PALEO LECTURE, PAGE 1
I. Tales Told by the Dead
A. Paleontology - study of ancient life
Fossil = any evidence of prehistoric life
1. Paleozoology - study of fossil animals
a. Invertebrate paleontology - study of fossil invertebrates (animals without a vertebral
column)
b. Vertebrate paleontology - study of fossil vertebrates (animals with a vertebral column)
2. Paleobotany - study of fossil plants
a. Palynology - study of pollen and spores (some also include marine one celled "plants"; i.e.
acritarchs, dinoflagellates, tasmanites, silicoflagellates, diatoms, ebridians, calcareous
nannoplankton/coccoliths)
3. Micropaleontology - study of small fossils (includes many groups mentioned under
palynology and also foraminifera, radiolaria, chitinozoa, graptolites, pteropods (gastropods),
ostracods (crustaceans), conodonts
B. Objectives of the paleontologist
1. Identification
2. Determine Form (= Morphology) and Function
3. Association of plants and animals and environmental reconstruction (paleoecology)
4. Evolution in Various Organisms
5. Dispersal and distribution of plants and animals through space and time (including studies of
paleozoogeography/paleogeography and biostratigraphy)
6. Correlation and Dating Rocks
7. Studies of Geochemistry - especially changes in ocean chemistry due to actions of organisms
C. Prerequisites/Preferred Conditions for fossilization:
1. Relatively abundant organisms
2. Presence of hard parts
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3. Avoid chemical and physical destruction
- rapid burial, typically within a relatively low energy depositional environment
- preservation depends on Eh/pH environment; plants often preserved within acidic and reducing
conditions; calcareous shells and bones typically within non-acidic
D. Types of Hard Parts
1. Plants
a. Cellulose - fibrous polysaccharide forming cell walls
b. Lignin - complex polymer binding cellulose fibers
2. Invertebrates
a. Organic Compounds include:
a1. Chitin = nitrogen-containing polysaccharide (carbohydrate) forming fibrous molecules; Ex.
= arthropods
a2. Scleroproteins = fibrous proteins such as collagen (Ex. = graptolites) and conchiolin (Ex. =
molluscs)
b. Minerals include:
b1. Calcium carbonate = forms intergrowth of crystals in an organic matrix; includes calcite
(Ex. = echinoderms) and aragonite (Ex. = some molluscs; aragonite is a chemically-unstable
mineral and typically recrystallizes to calcite)
b2. Opaline silica = often occurs as spicules (discrete parts; Ex. = some sponges) or forms
coherent network (ex. = radiolarians)
3. Vertebrates
a. Bone = collagen (a scleroprotein) hardened by mineral salts (mostly calcium phosphate);
with cellular structure
b. Cartilage = a resilient, partially fibrous protein; usually not preserved
c. Teeth = with dense calcium salts overlain by enamel (almost pure calcium phosphate and
carbonate)
E. Types of Fossil Preservation
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1. Unaltered
a.Unaltered Soft Parts
- unstable organic compounds such as carbon, hydrogen and oxygen
- rarely preserved; sometimes within permafrost (Ex. = mammoths) or glaciers, mummification
in dry caves (ground sloths), tanning by humic acids in peat (Ex. = "bog people"), within
anaerobic aqueous environments (such as the "limnic stagnation deposits" in the Eocene German
"brown coal" at Messel), within oil seeps, and in amber
b. Unaltered Hard parts (Durapartic Preservation)
- preserve original calcium carbonate or calcium phosphate "hard parts" such as bone (ex. = La
Brea tar pits, California), shells, "coralline" algae; relatively rare
2. Altered - more typical case.
a. Petrification includes:
a1. Cellular Permineralization (Impregnation) = percolating groundwater introduces minerals
(ex. = silicates, carbonates, iron compounds, phosphates) into the pore spaces (especially
permineralize calcareous shells with calcite; also wood and bone often permineralized)
Coal Balls = permineralize uncompacted peat with calcium carbonate; especially important for
Carboniferous plant studies from bituminous coal beds
a2. Recrystallization = change form and/or size of original crystal structure; Ex. = conversion
of aragonite to calcite often destroys fossil detail
a3. Replacement = percolating ground water dissolves hard parts and replaces them with
different minerals; Minerals involved include carbonates, silicates, iron oxides such as hematite
and "limonite", pyrite, and collophane
b. Carbonization - volatile components (hydrogen, oxygen, nitrogen) decrease and the outline of
the animals is preserved as a carbon film; scleroprotein, chitin, cellulose and lignin may be
carbonized; often combines with petrification
Coalified Compressions - plant cell walls collapse after deposition; cause loss of soluble
materials with residues altering to black, coaly deposits
3. Traces of Animals
a. Molds and casts
Mold - impression of skeletal (or skin) remains in an adjoining rock
External mold = impression of outer side
Internal mold (steinkern) = impression shows form or markings of inner surface
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Cast - original skeletal material dissolves and cavity (mold) fills with material
Endocast- natural infilling of cranial cavity (may study brain evolution in fossil mammals)
b. Ichnology - study of trace fossils (Ichnofossils = tracks, trails and burrows of organisms)
c. Coprolites - fossil excrement of animals; may contain undigested remains of food
F. Pseudofossils
- many rocks and rock structures look like fossils, but aren't!
- the following represent a few sedimentary features that may be confused for fossils:
1. Differential Weathering
- weathering of rock and mineral surfaces often yield fossil-looking features
2. Nodules
- formed by filling voids in the sediment and incorporation of sedimentary materials within the
sedimentary body
a. Chert Nodules
- microcrystalline quartz; typically found along bedding planes in limestone
b. Septaria
- large nodules with radial and concentric cracks in their centers
- Melikaria are boxwork patterns of material filling septarian cracks; may be all that is left after
weathering of the septaria
c. Rosettes
- radiating macrocrystalline bodies of discoidal or spherical shape, consisting essentially of one
mineral (typically pyrite, marcasite, barite, or gypsum)
3. Concretions
- mineral growth within sediment often forms structures that resemble bones, turtle shells, logs,
etc.
4. Dendrites
- precipitation of manganese oxide along bedding planes creates fern-like patterns
II. Rocks, Fossils and Ages
A. Biases of the Fossil Record
PALEO LECTURE, PAGE 5
- certain environments and processes preferentially preserve fossils; collecting techniques are
also biased
1. Hard Parts - soft-bodied organisms rarely fossilize
2. Preferential environments
- those with rapid burial
a. Aquatic environments preferentially preserved; especially shallow waters of continental
margins and inland seas, deltas, lagoons, rivers (especially floodplains), coal swamps and lakes
- typically lower-energy (finer grain size) environments with best preservation; Ex. = limestone,
shale, siltstone, chert
b. caves and fissure fillings also good for preservation
c. Konservat-Lagerstätten
- fossil localities exhibiting exceptional preservation
- fossilization often takes place under anaerobic conditions and/or within fine-grained sediments
- some examples include the Burgess Shale (Cambrian; British Columbia, Canada), Mazon Creek
(Pennsylvanian; Illinois), Solnhofen Limestone (Jurassic; Germany), Messel (Eocene; Germany)
and La Brea (Pleistocene; California)
3. Preservational Biases
- most fossils are known from species that were common, widespread and long-lived
4. Collecting Biases
a. best fossil hunting is often in erosional areas such as "badlands" of deserts and semiarid areas
(where you can see the fossils)
b. collecting techniques may be biased to large animals, small animals or animals from certain
paleoenvironments
B. Geologic Time
1. Relative Dating Techniques
- sequence geologic events
a. Biostratigraphy - see section below
b. Lithostratigraphy - correlation based on rocks
Correlation is often Accomplished by Use of:
PALEO LECTURE, PAGE 6
b1. Key (Marker) Beds - distinctive bed which is nearly the same age everywhere; Exs. =
volcanic ash, tillite
b2. Unconformities - deposits resting on unconformities (erosional surfaces) are of similar
age; often "global" unconformities are due to marine regressions [Eustatic (worldwide) lowering
of sea level]; unconformities can be located in subsurface by seismic surveys
c. Formal Lithostratigraphic Units - rock-stratigraphic units
c1. Formation - fundamental rock-stratigraphic unit; with mappability and lithologic constancy
c2. Member - subdivision of formation; may be mapped locally
c3. Group - contains several formations united on basis of similar characteristics
c4. Supergroup - composed of several groups
2. Absolute (Actual) Dating Techniques
- yields dates in years
a. Radioactivity
a1. Isotopes - forms of an element with same number of protons, different numbers of neutrons
a2. Radioactive Decay - atoms change to another element by releasing subatomic particles and
energy; parent isotope decays to daughter isotope at a constant rate
a3. Radiometric Dating - measure amount of parent materials relative to their daughter products
Half Life - time required for isotope to decay to half its original amount
- in paleontology often use potassium-argon (especially on volcanic rocks) and Carbon-14 (for
Pleistocene/Holocene deposits)
Notation:
Kiloannum (plural = Kiloanna; kilo an) = Ka = thousands of years in the radioisotopic time scale
Megannum (plural = Meganna; mega an) = Ma = millions of years in the radioisotopic time
scale; M.Y. (or m.y) = millions of years, without reference to the radioisotopic time scale
Gigannum (plural = Giganna; giga an) = Ga = billions of years in the radioisotopic time scale
b. Magnetic Stratigraphy
b1. Earth's Magnetic Field due to motions of liquid, iron-rich outer core (behaves like bar
magnet with north and south pole)
PALEO LECTURE, PAGE 7
b2. Magnetic Reversal - reversal of polarity in earth's magnetic field; is recorded in iron-rich
igneous and sedimentary rocks (Normal Interval = polarity same as todays; Reversed Polarity =
polarity opposite to todays)
b3. have constructed Paleomagnetic Polarity Scale based on magnetic reversals and "tied" with
absolute dates (Ex. = Text, p. 34)
Chrons = larger intervals defined by magnetic stratigraphy
3. Chronostratigraphic Units - body of rock representing a particular interval of time
Time Unit
Eon
Era
Period
Epoch
Age
Chronostratigraphic Unit
Eonathem
Erathem
System
Series
Stage
D. Geologic Time Scale
- learn Time Scale (Last Page of Lecture Notes)
E. Biostratigraphy ("Stratigraphic Paleontology")
1. Biostratigraphic distributions are controlled by:
a. Evolution
b. Paleoecology - no organism inhabits all environments
b1. Facies-controlled organisms = restricted to particular sedimentary environments (often
with slow evolutionary change)
b2. Biofacies = facies distinguished on the basis of their fossils (Ex. = reef biofacies - may
have corals, coralline algae, stromatoporoids, rudist bivalves)
2. Biostratigraphic Units
- body of rocks delimited from adjacent rocks by their fossil content
- often use fossils for Correlation (matching stratigraphic sections of the same age)
a. First appearances of fossils may be due to 1) evolutionary first occurrence 2) immigration
FAD = First appearance datum FOD = First occurrence datum
b. Last appearance of fossils may be due to 1) extinction event 2) emigration
LAD = Last appearance datum
LOD = Last occurrence datum
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c. Biozone
- basic unit of biostratigraphic classification
- based on the distribution of Index Fossils (fossils characteristic of key formations; should have
short time span, wide geographic range, independent as possible of facies, abundant, rapidly
changing and with distinctive morphology)
Types of Biozones Include:
c1. Assemblage Zones - strata grouped together on the basis of an assemblage of forms
Oppel Zone - interval of common occurrences of all or a specified portion of the taxa
Mammal age - geochronologic unit based on an association of fossil mammals considered to
represent a particular interval of geologic time; important for correlating Cenozoic fossil
vertebrate faunas worldwide
c2. Range Zones - plot stratigraphic range of fossil(s)
Teilzone = partial, local range zone
Taxon Range Zone (Acrozone) - total horizontal and vertical range of a taxon
Concurrent range zone - overlapping ranges of specified taxa
- Taxon and Concurrent Range Zones are most important range zones
c3. Acme Zone (Peak Zone, Abundance Zone)
- grouped together because of abundance of certain forms
3. Major Fossils used in Biostratigraphy
- best are pelagic [planktonic (floating) or nektonic (swimming)] forms
a. Macrofossils
- ammonites (Permian and Mesozoic)
- land mammals and plants (Cenozoic)
b. Microfossils
- most important include foraminiferans, radiolarians, palynomorphs (pollen, spores,
dinoflagellates, acritarchs, calcareous nannoplankton), conodonts
4. Quantitative Biostratigraphy
- use statistics to compare the degree of similarity between fossil faunas
- use Similarity Coefficients including:
a. Simpson Coefficient = C/(N1+N2)
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b. Jaccard Coefficient = C/(N1+N2-C)
c. Dice Coefficient = 2C/(N1+N2)
d. Otsuka Coefficient = C/square root of N1N2
WHERE: C = number of items in common
N1 = number of species in the smaller sample
N2 = number of species in the larger sample
The larger the values of the coefficients calculated from two faunas when compared, the closer in
age they are considered to be. But it is difficult to correlate quantitatively without determining
the relative value of the index fossils!
III. Continents Have Moved and Climates Have Changed
A. Paleobiogeography
- study of the ancient geographic distribution of organisms
1. Differences in distribution are due to
a. Barriers to organism dispersal - include physical barriers (Ex. = land and water barriers) and
environmental barriers (i.e. latitudinal and temperature changes)
b. Historical Factors - evolution of different organisms in different regions, etc.
2. Ancient Faunal Provinces
- often classified in modern ecosystems on the basis of the number of endemic species (=
organisms confined to one biogeographic unit)
a. Faunal Realm - largest biogeographical unit; over 75% endemic species
b. Faunal Region - between 50% and 75% endemics
c. Faunal Province - between 50% and 25% endemics
d. Faunal Subprovince - less than 25% endemics
- these classifications not typically used for fossil assemblages
3. Influences of Plate Tectonics
- one of major pieces of evidence for the presence of supercontinents was the common
distribution of plants (EX.= Glossopteris flora) and animals (the aquatic reptile Mesosaurus) on
the "Gondwana continent"
PALEO LECTURE, PAGE 10
a. Closing Oceans
- convergent plate margins often cause greater similarity of organisms
b. Opening Oceans
- continental fragmentation often leads to fragmentation of ranges of organisms and increasing
evolutionary dissimilarity through time
c. Accreted Terrains
- accreted (suspect) terrains are caused where microcontinents suture to other continental plates
- individual accreted terrains are often recognized by their distinctive (exotic) fossil faunas
d. Vicariance Biogeography
- modern distribution of organisms is largely due to "vicariating" (fragmenting) the ranges of
organisms (due to plate tectonics, ice ages, etc.)
B. Paleoecology
1. Ecology - study of the factors that govern the distribution and abundance of organisms
2. Paleoecology - the relationships between species represented in the fossil record and the
environments in which they inhabited
3. Taphonomy - all aspects of the passage of organisms from the biosphere to the lithosphere
a. Taphonomic Processes
a1. Physical Processes
- examples include mechanical breakdown of organic material by waves and currents, and burial
by sediments
a2. Chemical Processes
- examples include alteration of shell mineralogy, and leaching of shells and skeletons by
groundwater
a3. Biological Processes
- examples include destruction of hard parts by scavengers, and breakdown of skeletons by the
action of organisms (boring algae and sponges, etc.)
b. Taphonomic Biases - certain environments and taphonomic processes preferentially preserve
fossils; collecting techniques are also biased
b1. Preferential environments - Aquatic environments preferentially preserve fossils
b2. Preservational Biases - most fossils are known from species that were common,
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widespread and long-lived
b3. Time Averaging - fossil assemblages will be less similar to the living community the
greater the temporal variation of the living community and the longer the time averaged in the
fossil assemblage
b4. Collecting Biases - best fossil hunting where rocks and sediments are exposed; can avoid
biases by bulk collecting matrix and estimating proportions of fossils by constructing quadrants
or line transects
c. Size Distribution - often fossils are size-sorted due to current action; Micromorph Faunas
consist of unusually small individuals of species whose size is due to unusual environmental
factors
4. Sedimentary Environments - portion of the earth's surface with distinctive physical, chemical
and biological characteristics
a. Facies -body of sediment or rocks with distinctive characteristics
Facies Models - summary of specific sedimentary environments
b. Walther's Law - the vertical sequence of rocks may reflect the horizontal succession of
environments/facies
5. Biologic Criteria
- must be cautious in environmental interpretations based on fossils
- modern ecosystems are characterized by biocoenoses ("life assemblages"); paleontologists find
primarily thanatocoenoses ("death assemblages", or taphocoenoses)
a. Habitats - environments inhabited by life
b. Species relationships
Ecological niche - way in which a species relates to its environment
c. Ecologic Community - populations of several species living together in a habitat
- paleontologists do not observe fossil communities ("paleocommunities"); what they observe are
assemblages of fossils (fossils that occur together repeatedly define fossils assemblages)
c1. Ecosystem - organisms and their physical environments
Fauna - animals of an ecosystem
Flora - plants of an ecosystem
Biota = flora + fauna
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c2. Diversity
- number of species that live together in a community; tropical climates contain more diverse
plant and animal communities
Diversity = number of species/number of specimens
c3. Food chains - sequence of nutritional steps in an ecosystem
Trophic Level - position in food chain; organisms from lower trophic levels have more potential
for fossilization than those from higher trophic levels (because organisms from lower trophic
levels are more numerous)
c4. Food webs - nutritional structure of ecosystem in which more than one species occupies
each level
Competition - two species vie for limited environmental resources
Autotrophs (Producers) = manufacture their own food; "plants"; form lowest trophic level and
constitute the base of the biomass "pyramid"
Heterotrophs (Consumers) = feed on other organisms; consist of "animals" (much energy is lost
cycling through higher trophic levels, and therefore with fewer organisms)
Herbivores = feed on producers
Predation = effect of a predator on a prey species
Carnivores = feed on other consumers by predation
Parasites = derive nutrition from other organisms without killing them
Scavengers = feed on dead organisms
Commensalism = biological association beneficial to one but does not hurt the host
Symbiosis = mutual benefit to both participants
c5. Succession = changes due to modification of the environment by organisms
Stages of Succession Include:
Pioneer Stage: with abundant, rapid-growing, short-lived species with abundant offspring (rstrategists)
Mature Stage: with the most diversity
PALEO LECTURE, PAGE 13
Climax Stage: slower-growing, larger, longer-lived species with fewer offspring (K-strategists)
replace organisms of earlier stages
6. Limiting factors
- environmental factors controlling species distribution
- includes chemical, physical and biological factors
Organism Distribution (Especially Marine) Depends Upon the Following:
a. Seawater Properties - Density and Viscosity
Density of aquatic organisms typically equals water density
Viscosity - influences shape and feeding (there are many "filter feeders" in aquatic environments,
due to the viscosity of water allowing food to be held in suspension)
b. Salinity
- usually measured in parts per thousand (0/00); average seawater salinity is 35 0/00 but varies
from 0 to 270 0/00
- in Geochemical Studies of Paleosalinity use boron (greater in saltwater); other trace elements;
type of organic matter; carbon and oxygen isotopes [freshwaters depleted in heavy carbon
(C-13) and heavy oxygen (0-18)]
- in Biological Studies use stenohaline (restricted by salinity; organisms internal "salinities"
equals surrounding water salinity; if rapid change cells may not function) versus euryhaline
(salinity tolerant) organisms
c. Temperature
- water moderates temperature
- in cold-blooded organisms, an increase in temperature of 10°C often causes metabolic activity
to double
- in warm-blooded organisms there is little metabolic change with temperature change
- temperature influences reproductive cycles
- in Geochemical Studies of Paleotemperature use 18O/16O (less with greater temperature; most
important for determining paleotemperatures); boron and bromine greater if greater
temperature; Calcium/Magnesium and Calcium/Strontium ratios are less if the temperature is
increased
- in Biological studies of paleotemperature use stenothermal (temperature intolerant) versus
eurythermal (temperature tolerant) organisms; also may look at species diversity (greater in
warmer environments) or morphology (body form reflects environmental factors)
d. Dissolved Gases
- concentrations depend on atmospheric concentration; solubility of gas; water temperature and
salinity
d1. Nitrogen (N) - most abundant dissolved gas; required by plants in ionic form
d2. Oxygen (O) - enters sea by photosynthesis, river water, atmosphere; all organisms use
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oxygen during respiration; oxygen at maximum near surface, minimum at about 7001,000m Oxygen; approximately 6 to 10 ppm; warmer, saltier or organic debris-rich water
with less oxygen
d3. Carbon Dioxide (CO2) - enters sea from organism respiration, atmosphere and rivers;
removed by plants for photosynthesis and used by organisms to make shells; increases to
approximately 1,000m; increased CO2 leads to Greenhouse Effect (increase temperature)
d4. Hydrogen Sulfide (H2S) - produced by anaerobic bacteria
e. Light
- Photic zone = zone of light penetration
Euphotic zone = upper illuminated layers of water in the photic zone; receive sufficient light to
support photosynthesis; usually 10-60 meters but clear tropical waters may be greater than
100 meters
- Aphotic zone = zone in which light does not penetrate
f. Pressure
- pressure increases approximately 1 atmosphere per 10 meters
- affects vertical migration of organisms, bacterial decomposition, production of shells (CCD =
carbonate compensation depth)
g. Depth
- deep water stores carbon, nitrate, phosphate
Paleobathymetry - the ancient water depth may be determined by type of body fossils and trace
fossils present
h. Water energy, turbidity and sedimentation rates
- affects distribution of food and nutrients; types and morphology of organisms present
- amount of suspended sediment especially affects filter-feeders
- nature of substrate affects type of infauna (live in substrate) or epifauna (live on substrate;
sessile or vagile benthonic) present
7. Paleoclimatology
- study of ancient climates
- utilizes sedimentologic, paleontologic and geochemical data to reconstruct ancient temperature,
wind patterns, precipitation and evaporation
8. Chemical Cycles in Earth System History
Chemical Reservoirs - bodies of key elements and compounds in the Earth system that shrink or
expand as fluxes between them change
- these reservoirs are influenced by the following:
PALEO LECTURE, PAGE 15
a. Photosynthesis and Respiration
Photosynthesis - process by which plants use the energy of sunlight to produce sugars from
carbon dioxide and water; oxygen is a by-product of this process
Respiration - opposite chemical reaction versus photosynthesis; organisms oxidize sugars in
order to release their energy
b. Carbon Dioxide and Oxygen Cycles
- if no dead plant tissue is buried, it decomposes and carbon dioxide returns to the atmosphere
- if dead plant tissue is buried (such as in swamps or anoxic marine environments), it upsets the
balance between photosynthesis and respiration (with the amount of carbon dioxide in the
atmosphere shrinking and with increase in oxygen levels)
- weathering of minerals removes carbon dioxide from the atmosphere (enhanced by mountain
building, warm climates, high rates of precipitation, and more vegetation)
- the initial spread of forests during the Devonian intensified weathering, depleted the
atmospheric reservoir of carbon dioxide; this reduced greenhouse warming and probably
contributed to the cooler climate conditions and formation of the Late Paleozoic "Ice Age"
c. Methane Cycles
- methane is a powerful greenhouse gas
- when global warming melts masses of methane hydrate on the seafloor, the addition of methane
to the atmosphere produces further global warming
d. Negative Feedback in Carbon Dioxide and Global Warming Cycles
- when climate warms, chemical weathering accelerates (extracting carbon dioxide from the
atmosphere) and the amount of evaporation increases on the ocean (which further accelerates
weathering on land, extracting more carbon dioxide from the atmosphere)
e. Submarine Volcanism versus Seawater Chemistry, Mineralogy and Types of Organisms
- seawater circulating around mid-oceanic ridges transfers calcium to the seawater; magnesium is
extracted from the water and becomes locked in the rocks [therefore with more seafloor
spreading there is a rise in sea level (more rocks produced) and a decrease in the
magnesium/calcium ratio (more magnesium extracted from seawater)]
- with increased marine volcanism, the low magnesium/calcite ratios produce "Calcite Seas", in
which calcite forms oolites and marine cements and organisms with calcite skeletons become
successful reef builders (the lowest magnesium/calcite ratio of the Phanerozoic was during the
Cretaceous, which contains much more "chalk" than any other system)
- when the total volume of volcanics at mid-oceanic ridges is low, aragonite and high-magnesium
calcite is more abundant; "modern" types of corals, with aragonite skeletons, are more abundant
during these periods of Earth history
IV. Groups, Names and Relationships
PALEO LECTURE, PAGE 16
Taxonomy - process of classification and naming organisms; typical classification of organisms
is by their relationship to one another (= "natural" classification)
Systematics - grouping organisms according to the extent to which they are related
- the classification of organisms has traditionally used the Linnaean System, formulated by
Carolus Linnaeus in the 1700's (Many biologists and paleontologist are now abandoning the
Linnaean System, due to the influence of Cladistic Taxonomy )
A. Taxa (singular = taxon) in the Linnaean System
1. Domain
- in some recent classifications, constitutes the highest taxonomic category
- often include the Domains Archaea/Archaebacteria, Bacteria/Eubacteria, and Eucarya
2. Kingdom
- in many classifications is the highest taxonomic category
- there are typically 5 to 6 recognized kingdoms [Monera (often classified as Domain or
Kingdom Archaea/Archaebacteria and Domain or Kingdom Bacteria/Eubacteria); Domain
Eucarya includes the Kingdoms Protoctista (Protista), Fungi, Animalia (Metazoa), and Plantae
(Metaphyta)]
3. Phylum
4. Class
5. Order
- superorders often end in -ica, orders in -ida (-formes in many vertebrate orders) and suborders
in -ina
6. Family
- superfamilies often end in -oidea, families in -idae and subfamilies in -inae
- To convert Latin names to English use suffix "-id"; if it resembles a group use "-oid"
7. Genus
- group of interrelated species; plural = genera
8. Species
- fundamental unit of taxonomy
Binomen = genus + species names; there may also be subspecies
a. There are two concepts of what constitutes a species:
a1. Biogeographic-Genetic Species = population of individuals that can interbreed and
produce viable offspring; are spatially segregated and genetically isolated from similar adjacent
groups
PALEO LECTURE, PAGE 17
a2. Linnaean Species = based on discontinuity in the range of variation in the form
(morphology) of organisms; is typically used in paleontological studies
B. Naming a Taxon
-use International Rules of Zoological or Botanical Nomenclature
1. Each genus + species has a name independent of change; names are Latinized
2. Each genus + species will have separate names
- No genus name can be duplicated
3. Different names will not be applied to one species or genus
Synonym = two or more different names given to the same animal; use Law of Priority to
determine which is correct
4. Each genus + species must have a Type (= primary name bearer)
a. Type species of a genus - composed of one of its species
b. Type specimens of species - is a particular specimen
Holotype = single specimen serves as the name bearer (is now a rule)
Paratypes = other specimens which serve to characterize a species
5. Author citations
a. Cite authors name after taxon and first year of publication
b. If author's species transferred to another genus then place original author's name in
parentheses
C. Theories of Taxonomy
- what taxonomists seek is the establishment of Monophyletic Groups (species that share a
common ancestry that are grouped together taxonomically; the grouping that includes the
ancestor and its descendants is often termed a Clade)
- taxonomists want to avoid Polyphyletic Groups (group evolved from two or more distinct
ancestors) and Paraphyletic Groups (groups with a common ancestry but with one or more
descendant groups excluded; include many modern groups)
1. Evolutionary Taxonomy/Systematics
- this is Darwin's taxonomy
- you must classify populations ("taxa") rather than individuals or characters
- first you classify a phenotype (the characteristics) and then you infer the genotype (its genetic
PALEO LECTURE, PAGE 18
constitution)
2. Phenetics (Numerical Taxonomy)
- classify organisms by purely mechanical or mathematical means
- select a group of characters to describe the Operational Taxonomic Unit (OTU), construct a
similarity matrix, and then display the results as a phenogram or dendrogram
- But is it a "natural" classification system?
3. Cladistic Taxonomy (Phylogenetic Systematics; Hennigian Systematics)
- formulated by entomologist Willi Hennig
- Hennig stated that primitive characters are of no use in taxonomy (a "character" is any definite
aspect of a particular organism)
- The larger the number of nonprimitive ("shared derived" or synapomorphic) characters shared
by two subgroups the more closely related the subgroups (character = any recognizable trait of an
organism; Character State = presence or absence of trait or alternative ways in which a character
may be expressed)
a. Types of Characters
a1. Discrete characters - have a limited number of possible values
Binary Characters - have two states (Ex. = presence or absence of a feature)
Multistate Characters - have more than 2 states (Ex. = blue, green and brown eye color)
a2. Continuous Characters
- measurements on a continuous scale (Ex. = size of organisms)
- continuous characters are hard to use and interpret
b. Types of Phylogenetic Traits
b1. Plesiomorphy = primitive trait
Symplesiomorphy = shared primitive trait
b2. Apomorphy = specialized or derived trait
Autapomorphy = specialized trait unique to one group
Synapomorphy = specialized trait shared by two or more groups
c. Sister Groups
- two groups united by the presence of one or more synapomorphic characters
- Sister Groups share a common ancestor and are each other's closest relatives
PALEO LECTURE, PAGE 19
d. Polarity
- direction of evolutionary change
- is determined by the stratigraphic sequence, ontogeny (organisms life history, especially
embryological development), outgroup comparison [characters are derived if they do not appear
in closely-related "outgroups" (i.e. taxa that are not part of the group under consideration but
share a common ancestry)], character analysis within groups and anatomical progression
(Morphocline = characters that vary quantitatively within a group; ex. = body size, limb
proportions)
e. Parsimony
- the best hypothesis is the one with the fewest number of processes (the majority of characters
rule; also, choose and weight the characters of "most importance")
f. Cladogram
- diagram that depicts recentness of divergence of subgroups based on the number of shared
derived characters (but is not based on the absolute time scale)
g. Why some taxonomists think cladists are full of bull:
- Cladists tend to ignore stratigraphy of the fossil record
- it is very difficult to assess relationships from the initial stages of major adaptive radiations
(plesiomorphic, autapomorphic and synapomorphic characters are difficult to differentiate)
- Cladists hope that what they deal with is Divergent Evolution (evolutionary diversification) and
that evolution cannot be reversed (Dollo's Law); Dollo's Law may typically be true (but it is
tough to judge)
There are types of evolution that may confuse cladists:
Parallel Evolution = two closely related organisms undergo a similar evolutionary change
through time
Convergent Evolution (adaptive convergence) = close morphologic similarity arises between
two unrelated groups that take on similar life habits (Homeomorphs)
D. Molecular Phylogeny
- sequences of bases in chains of genetic material (DNA and RNA) and amino acid sequences of
proteins are diagnostic for each organism (the closer the relationships the greater the genetic
similarities)
- random mutations substitute various amino acids in molecules that is more or less directly
proportional to time (therefore there may be "Molecular Clocks")
- may compare the proteins in preserved tissues up to or compare the proteins of living forms to
determine their relationships (latter is most often used)
E. Adaptation and Functional Morphology
1. Adaptation
- the "fitness" of an organism; how organisms cope with changing environmental conditions,
invade new environments, and function more efficiently in a given environment
PALEO LECTURE, PAGE 20
a. Why adaptation occurs:
a1. Must have features that allows the organism to survive in particular environments
a2. Red Queen Hypothesis - formulated by Leigh van Valen; because of competition for
resources with other organisms, a species must continuously improve its adaptation or becomes
extinct (even in stable environments)
b. Evidence for Adaptation
b1. Morphology - body parts of an organism are "designed" to fit the environment in which
they live
b2. Convergent Evolution - independent evolution of similar morphologies that function
similarly
c. Organisms are not "completely" adapted to their environments because:
c1. they are constrained by their ancestry
c2. there are multiple uses of organs - but in changing environments this is not all bad!!!!
2. Functional Morphology
- the study of the relationship of form to the functions that organism or their component parts
perform
a. Morphology (form) is controlled by:
a1. Adaptation - organisms morphology is restricted by environmental constraints
a2. Phylogeny - organisms morphology is restricted by their evolutionary history
a3. Growth
Isometric Growth - all parts grow at the same rate
Allometric Growth - some parts grow faster or slower than others (found in most higher
organisms)
b. Studying Morphology
b1. Theoretical Morphology
- often uses a Paradigm (model or pattern); computer programs are helpful for studying a wide
variety of parameters
b2. Comparison with Living Organisms
PALEO LECTURE, PAGE 21
- is very helpful but assumes that modern organisms have similar morphological features and
constraints as their fossil "counterparts" (sometimes a bad assumption!!!)
F. Mechanisms of Evolution
Evolution = (1) historical changes in structure, function and adaptation (2) genetic changes and
processes of selection and population dynamics
1. History of Evolutionary Theory
a. Jean-Baptiste Lamarck (1744-1829) - French naturalist; developed theory now known as
Lamarckism (theory of inheritance of acquired characteristics)
b. Thomas Malthus (1766-1834) - English clergyman and economist; wrote "Essay on the
Principle of Population"; introduced concept that population exhibits exponential growth,
whereas food production exhibits linear growth; population expands to limits set by famine, war
and disease
c. Alfred Wallace (1823-1913)- codiscoverer of the theory of natural selection independent of
Darwin; also a prominent zoogeographer
d. Charles Darwin (1809-1882) - most naturalists of his time were "special creationists"; as
ship's naturalist on the H.M.S. Beagle (1831-1836) developed the foundation of his theory of
evolution; Read Malthus' Essay on Population; Wrote "The Origin of species by means of
Natural Selection" in 1859
Darwin's facts and deductions include:
- organisms tend to increase in numbers by a geometric ratio
- in spite of the tendency to progressive increase the number of individuals within a species tend
to remain approximately constant.
- Deduction: Since more young are produced than can survive there must be a competition for
survival ("Struggle for Existence")
- all organisms vary; some variations are inherited
- some individuals fail to survive, others live to reproduce (natural selection)
Summary of Darwinian Evolutionary Theory: New species arise from preexisting ones as a
result of natural selection acting on inherited variations
e. The Synthetic Theory (Neodarwinism)
- developed in the 1930's and 1940's by Theodosius Dobzhansky, Ernst Mayr, George Simpson
and Julian Huxley
- stated that the determinants of traits on which natural selection acts are genes (heritable units of
information governing structure, development and function)
- variation is due to gene mutation (also now theorized that tandem multiplication of nucleotides
and gene duplication is important)
PALEO LECTURE, PAGE 22
- also population structure and distribution is important in the development of new species
Natural Versus Sexual Selection
- natural selection depends on fitness of the organism to its environment
- sexual selection depends on attractiveness to females (one may work against the other; Ex. =
elaborate plumage of birds)
f. The Neutral Theory
- developed in the late 1970's by Motoo Kimura
- states that most genetic differences neither foster nor hinder an organisms survival and their
persistence or elimination in a population is a matter of chance
- genetic differences have an adaptive effect that supplies abundant raw material for the creative
force of natural selection
g. Punctuated Equilibrium versus Phyletic Gradualism
g1. Phyletic gradualism
- rates of evolution are regular
- is Darwinian Evolutionary Theory
g2. Punctuated equilibrium
- first proposed by Niles Eldredge and Stephen Gould during the 1970's
- says that evolution occurs in fits and spurts separated by long periods of little change
- problem in testing (sudden appearances in fossil record may be due to immigration rather than
rapid speciation)
- problem in classification (no classification system can show intermediate forms (only "species")
h. Mosaic Evolution
- first proposed by Gavin deBeer
- different parts of organisms do not change at a uniform rate in the course of evolution
- I interpret it as the middle ground between punctuated equilibrium and phyletic gradualism
2. Evolutionary Changes
a. Evolutionary Change is by means of (?):
a1. Phyletic Evolution (Anagenesis) - process by which a single lineage changes over time
a2. Speciation (Cladogenesis) - process by which a single species divides into two lineages
that become reproductively isolated from one another; preferred by proponents of punctuated
equilibrium
Clade - all organisms descended from a progenitor species
b. Peripatric Speciation
- Evolutionary changes are most likely within small, geographically isolated populations
PALEO LECTURE, PAGE 23
(therefore most important groups for establishing evolutionary patterns and processes are least
likely to be preserved)
- inbreeding leads to homozygosity (with recessive and dominant traits common and therefore
potentially rapid change)
- if an isolated population rejoins with the parent population again (sympatry), they must diverge
behaviorally and/or physically even more to survive
3. Microevolution versus Macroevolution
a. Microevolution = process of evolution within a single lineage
- involves natural selection between individuals
b. Macroevolution = process of evolution between groups
- involves higher taxonomic categories
b1. Species Selection - differential survival among a number of species that descended from a
common ancestor; if significant changes take place than assume there were a large number of
species involved in that competition
- Competition between groups is demonstrated by convergent evolution, mimicry (often nonpoisonous types mimic poisonous ones) and protective coloration (organisms camouflaged to
resemble environment)
- Evolutionary "Arms Race" = competition beween predators and prey leads to sequence of
evolutionary changes in both groups
b2. Trends in Macroevolution
- initially with low number of lineages and absence of competition (not much difference between
species)
- features become stabilized and are recognized as characters of families or orders
- adaptive radiation may give rise to tremendous increase in diversity during short time
b3. Cope's Law = size increase among warm-blooded animals
4. Evolution and Ontogeny
a. Ontogeny - life history of an organism (especially embryological development)
b. Embryos develop from general characters towards more specific ones
- in early stages of development animal embryos tend to be very similar
c. Haeckel's Law - ontogeny recapitulates phylogeny
- i.e., in its development from embryo to adult the individual passes through the evolutionary
stages of its ancestors (= Peramorphosis)
d. Paedomorphosis - early stages of the ontogeny of ancestors become the adult stage in
descendants (Ex. = some adult amphibians have larva-like form)
PALEO LECTURE, PAGE 24
G. Evolution in Earth History
1. Rates of Evolutionary Change
a. is probably irregular [Simpson, 1944, coined Bradytely (slow change), Horotely (medium
change) and Tachytely (rapid change) terms]
Darwin = unit for measuring evolutionary change; d = change by a factor of e per million years,
where e is the base of natural logarithms (very different rates for vertebrates; probably 0.02 to
400 d in "natural" settings)
b. Adaptive Radiation
- emergence of new structures and ways of life, or mass extinctions, often leads to "adaptive
radiations" with large increase in number of daughter species evolving
- major changes in life styles often due to relatively minor modification of skeletal features
- many clines with adaptive radiations followed by slow decline toward extinction
c. For determining evolutionary patterns and rates at the species level need (and is rarely
accomplished):
- sedimentary record complete with gaps less than 10,000-20,000 years
- total sequence probably exceeding 100,000 years
- good dating (especially radiometric)
- entire species range known with a record of ancestral and descendant species in the area
- geographical range of species known
- significant portion of skeletal anatomy known
2. Trends and Cycles
a. Trend - "unidirectional" changes
- Ex. = increase in oxygen content
- increased specializations of organisms through time
b. Cycles
- repetitive sequences (may greatly influence evolution)
b1. "Greenhouse"/"Icehouse" Cycles
- moving continents and expansion and contraction of ocean basins leads to "greenhouse"
(increased volcanism produces more CO2, which leads to a greenhouse effect with greater
temperatures)
- cycles 300 to 500 million years in length
b2. Sea Level Fluctuations
- transgressions (relative rise in sea level) and regressions (drop in sea level) may influence
evolution [regressions may place stresses on shallow-water marine organisms; "specialist"
PALEO LECTURE, PAGE 25
organisms usually with highest evolutionary rates just after the period of greatest transgression]
- Seismic evidence from passive plate tectonic margins indicates there are patterns of small-,
medium- and large-scale sea level cycles that produce unconformities (Vail Curves)
b3. Astronomical Cycles
- periods of increased bolide impacts (asteroids, comets) lead to extinction
3. Extinction
- most likely in species with small populations and live in limited geographic areas (population
size related to trophic level and body size with carnivores most likely to become extinct and
small herbivores least likely)
a. Types of Extinction
a1. Background Extinction
- probability of extinction is approximately constant through the life of a particular group but
rates vary from group to group
- therefore there is a "normal background rate" of extinction
a2. Mass Extinction
- there are six Phanerozoic episodes of major extinction
b. Reasons for extinction include:
b1. Competition
- difficult to determine even among living species
b2. Predation
- also tough to tell
b3. Environmental Deterioration
- climate change (Exs. = cooling trends, drop in sea level, oxygen-depleted deep ocean water
rises onto continental shelves, violent volcanism) causes mass extinctions
b4. Stochastic Processes
- says that origin and extinction of organisms is probabilistic (like a "flip of a coin")
- computer programs generating "artificial" phylogenies are much like "natural" clades
Ex. = Extraterrestrial causes - extinction by periodic bolide impacts or comets?
b5. Man
- important for past 11,000 years (?)
V. Earth's Oldest Remains
PALEO LECTURE, PAGE 26
A. Earth Origin
1. Age of the Earth - based primarily on Extraterrestrial Evidence:
a. Meteorites - extraterrestrial objects that fall to earth; most dated at approximately 4.6 Ga
b. Moon Rocks - oldest nearly 4.6 Ga
c. Oldest Rocks on Earth - oldest crustal rocks from Canada are dated at 4.04 Ga;
metamorphosed sediments in western Australia have zircon grains dated at 4.4 billion years old
2. Origin of the Solar System and Planets
Solar Nebula Theory - solar system formed from cloud of cosmic dust; rotated, became disc-like
and planets accreted
3. Formation of the Earth's Atmosphere was probably by:
a. Outgassing of earth's interior during Archean times by volcanic activity; produced water
vapor, nitrogen, carbon dioxide, etc.
b. Impact by cometary ice
c. Plant Photosynthesis - provides oxygen (but probably with little oxygen in the Precambrian)
4. The Oceans
- gases condense during Earth cooling; "modern" salinity obtained in Early Archean
- the Early Archean ocean were probably much warmer than that of today due to the presence of
abundant radioactive elements in the Earth's crust and the "Greenhouse Effect"
B. Organisms
- ordered (i.e. with cellular organization) living creatures
- "life" is a series of chemical reactions, using carbon-based molecules, by which matter is taken
into a system and used to assist the system's growth and reproduction, with waste products being
expelled
- life forms pass on their organized structure when they reproduce
C. Origins of Life
1. The Earth During the Archean Eon
- equable conditions for prebiotic evolution could have existed on Earth as long ago as 4.4 Ga
- Archean Earth was dominated by oceanic lithosphere with volcanic islands and small
microcontinents
- large amounts of CO2 may have led to a Greenhouse Effect, with atmospheric temperatures up
to 100°C or more (therefore NO polar icecaps; with permanently stratified stagnant iron-rich
PALEO LECTURE, PAGE 27
deep ocean waters and wind-mixed iron-poor surface waters)
- hot springs, submarine hydrothermal systems, and heated wind-mixed layers of the oceans may
have been areas where prebiotic evolution occurred
2. Origins of Life
a. Depends upon the synthesis of Carbon
- once carbon is synthesized, all other biogenic molecules may be formed (Organic Molecules are
complex, carbon-based molecules)
- elements most prominent in organic molecules are carbon, hydrogen, oxygen and nitrogen
b. Cellular Structure
b1. Cell
- a "container" filled with organic and inorganic molecules (= Protoplasm); the cell contains:
b2. Proteins
- built from amino acids; proteins are used as "building materials" and for chemical reactions
b3. Nucleic Acids
- includes Deoxyribonucleic Acid (DNA) and Ribonucleic Acid (RNA); provide information for
the structure of the organism and the means to pass on this information in reproduction
- DNA carries the genetic code of an organism, providing information for its growth and
metabolism; it has the ability to replicate itself in order to pass this information on to
subsequent generations
- RNA has several functions (carries genetic message of DNA to sites; assembles amino acids
into proteins; acts as a catalyst for chemical reactions), and because of this versatility was
probably the nucleic acid present within the earliest life forms (this earliest ecosystem is often
termed the "RNA World"); but RNA was eventually replaced by DNA as the genetic code (as
DNA is a more stable molecule)
b4. Organic Phosphorous Compounds - found in small amounts; transform light or chemical
fuel into energy
c. The Formation of Proteins
c1. Amino Acids
- mixture of methane, ammonia, hydrogen and water vapor (or nitrogen, carbon dioxide and
water vapor) in the presence of electricity or ultraviolet light leads to the production of amino
acids
- some meteorites also contain amino acids
- production of amino acids must take place in an anaerobic (devoid of free oxygen) environment
PALEO LECTURE, PAGE 28
c2. Proteins
- removing water from amino acids yields Polypeptides (protein-like chains)
- when polypeptides cool they form Microspheres (cell-like structures)
D. Kinds of Organisms
1. Prokaryotes
- single-celled organisms with their DNA loosely organized within the cell, are not bounded by a
membrane into a nucleus and they lack chromosomes
- reproduce by simple nuclear division of cells; meiosis absent
- range from 0.3 to 20 microns
- are often termed Monerans
- often divided into two Domains (or Kingdoms):
a. Domain/Kingdom Archaea/Archaebacteria
- superficially similar to eubacteria but differ greatly in their molecular (especially RNA)
sequences
- include the methanogens (tend to be found in highly saline environments), sulfur-metabolizing
bacteria and sulfate-reducing bacteria (found around hydrothermal vents)
- probably included the oldest life forms, which were probably thermophilic autotrophs (used
molecular hydrogen, carbon dioxide and sulfur compounds to produce energy, with optimal
growth at temperatures from 70° to 110°C); possible environments of origin include hot springs,
heated ocean waters, and hydrothermal vents
b. Domain/Kingdom Bacteria/Eubacteria
- contain the most commonly recognized or "true" bacteria and cyanobacteria
- evolved both thermophilic autotrophs in heated environments and photoautotrophs in shallow
marine environments (see discussion below)
- life originated at least as early as 3.5 Ga ago, as indicated by (mostly) Eubacteria
Evidence Includes:
b1. Megascopic Stromatolites
- Stromatolites are laminated structures formed by blue-green algae (cyanobacteria)
- the earliest Stromatolites come from the Swaziland Group of South Africa and the Pilbara
Supergroup of Australia (dated about 3.0 to 3.55 Ga)
b2. Permineralized Microfossils
- filamentous kerogen-rich microfossils similar to cyanobacteria occur in cherts of the Pilbara
Supergroup (Warrawoona Group) of Australia dated at about 3.4 Ga
b3. Biologically Produced Organic Matter
- organic carbon-13 values from the 3.0 to 3.55 Ga-old Swaziland and Pilbara sediments are
similar to those of modern cyanobacteria and photosynthetic bacteria
PALEO LECTURE, PAGE 29
2. Domain Eucarya
Eukaryotes = single- or multi-celled organisms with chromosomes made of DNA, RNA and
proteins contained within a membrane-bound nucleus
a. Characteristics
- with specialized structures (vacuoles, mitochondria, many with chloroplasts)
- oxidize sugars as a source of energy
- meiosis present = with two consecutive cell divisions by which the chromosomes are reduced
from the diploid number of somatic cells to the haploid number (half) characteristic of gametes
and spores
- sexual reproduction provides more variation that may potentially enable the species to better
survive environmental changes
- cells range from 3 microns to several millimeters
- the Domain Eucarya includes the Kingdoms Protista (Protoctista), Fungi, Plantae (Metaphyta)
and Animalia (Metazoa)
b. Origin of Eukaryotes
- nuclear membrane probably formed by invagination of cell membrane
- specialized structures (chloroplasts and mitochondria) probably developed from endosymbiotic
prokaryotes living within the cell membrane of archaebacterial prokaryotes
c. The Oldest Eukaryotes
- as oxygen built up in the Early Proterozoic atmosphere, due to the presence of photosynthetic
prokaryotes, the concentration of dissolved oxygen increased in the upper ocean; as a result more
nitrogen was oxidized to form nitrate (NO3-), which is an important nutrient for eukaryotic algae
(Cyanobacteria don't need nitrates, as they can use pure nitrogen (N2) for their metabolism)
- oldest known probable eukaryote is the corkscrew-shaped, cylindrical megascopic colonial alga
Grypania, from a 2.1 Ga-old banded iron formation in Michigan
- organic-walled microfossils of eukaryotic photoautotrophic plankton ("acritarchs") occur in
rocks slightly younger than those containing Grypania
E. Atmospheric Oxygen
- increased dramatically between 2.2 and 1.9 Ga-ago
- increase in atmospheric oxygen was very important for the development of more complex life
forms
1. Evidence of Increased Atmospheric Oxygen Levels Includes:
a. Paleosols
- analyses of iron oxides in soils older than 2.2 Ga indicate atmospheric levels of oxygen at 0.2%,
or 1% PAL (present atmospheric level is 21%); atmospheric levels in younger than 1.9 Ga-old
paleosols indicate 15% PAL, or about 3% total gaseous composition of atmosphere
b. Red Beds
PALEO LECTURE, PAGE 30
- oldest known thick redbeds at over 2.2 Ga; indicate oxidation of iron
c. Weathering Residues in Sedimentary Rocks
- no widespread deposits of placer uraninite are found in rocks younger than 2.3 Ga (uraninite is
unstable in the presence of free oxygen)
d. Metals In Black Marine Shales
- weathering of uranium and molybdenum on land in oxygenated environment would lead to
greater concentrations of these elements in seawater
- 2.5-2.7 Ga-old marine shales are low in uranium and molybdenum; those younger than 2.1 are
enriched (indicating presence of free oxygen)
e. Banded Iron Formations
- alternating chert and hematite/magnetite layers
- therefore oxidized (ferric) iron formed in marine basins (although there is some debate as to the
original oxygen content in BIF's)
- but Banded Iron Formations disappeared about 1.9 Ga-ago when oxygen content was supposed
to be increasing (BIF's may also be influenced by ocean stratification and therefore this may be
the source of conflicting data, or they may not have contained as much oxygen as some
geologists have claimed)
2. The Ozone Shield
- development of ozone (O3) prevented lethal radiation from reaching the Earth and was of major
importance in the development of life
F. Origin and Diversification of the Metazoa
1. Metazoa (Animalia)
- with specialized cells forming tissues (= metazoan organization)
- tissues are united into organs (except in simplest invertebrates)
2. Vendian Body Fossils and Trace Fossils
a. The Vendian Period (610-550 Ma ago) or Neoproterozoic
- beginning of Vendian Period with most intensive glaciation in Earth history (the
Varanger/Varangian or Marinoan Glaciation)
- later Vendian with relatively warm global climate, with major marine transgression and
development of extensive shallow marine environments, which led to a greater diversity of
organisms
b. Tracks and Burrows
- oldest undisputed metazoan traces found in Late Proterozoic rocks (680-900 Ma)
- Vendian trace fossil assemblages (Ichnocenoses) include feeding burrows, dwelling burrows,
crawling and grazing trails; differ from later Phanerozoic types with Vendian trace fossils
smaller, with shallow penetration into the sediment, and used different types of peristaltic motion
PALEO LECTURE, PAGE 31
(with hydrostatic skeletons or muscular contraction of the ventral side of the body)
c. Ediacara Fauna
- originally from Pound Quartzite of South Australia; later found in approximately 25 Late
Proterozoic localities worldwide (on all continents except South America and Antarctica)
- Vendian fossil record consists of moderately large, soft bodied invertebrates preserved in wellaerated shallow marine environments (unusual to preserve in this environment during later
Phanerozoic times, probably mostly due to absence of predators, scavengers, deposit feeders, etc.
during Vendian times)
- the structure and relationships of Vendian Fossils is greatly debated; hypotheses of their
relationships consist of the following:
c1. Vendian Fossils may be placed primarily within Modern Soft-Bodied Metazoans
- the "classical theory" says that Ediacara fossils can be placed in the Phylum Coelenterata
(classes Hydrozoa, Anthozoa, Scyphozoa, Conulata, medusae of uncertain systematic position,
and problematic Petalonamae), Phylum Annelida (Class Polychaeta), Phylum Arthropoda
(Superclass Trilobitomorpha or Chelicerata represented by the uncertain class and superclass
Crustacea, Class Branchiopoda), Phylum Pogonophora, Phylum Echiurida, as well as some forms
of uncertain position even at the level of phylum
c2. Vendian Fossils have NO recent modern Analogues
- Adolf Seilacher suggests the Ediacara fauna (the Vendobionta) have a unique organization
characterized by an extensive body surface developed by a very complicated relief and by a low
body volume due to their flatness ("pancake animals"); fossils have a foliated and quilted
construction to increase surface area
- flattened morphology, quilting and high surface/volume ratio allowed absorption of oxygen and
organic matter dissolved in the water by diffusion through the body wall; therefore did NOT have
a mouth, digestive, or respiratory organs
- some fossils may have had internal sand skeletons adapted to living on unstable sandy bottoms
(Seilacher's "rock in a sock" morphology)
3. The Tommotian Fauna
- often classified as the base of the Cambrian
- first fossils of the "Cambrian Explosion"; first abundant record of hard parts, with thousands of
taxa represented
- late Proterozoic and earliest Cambrian with fossil tubes of various composition
- the Tommotian Fauna includes "small shelly fossils"; with disjunct sclerites of calcium
carbonate or calcium phosphate ("tommotiids" are phosphatic sclerites that evidently articulated
to form an exoskeleton), mollusc-like shells (monoplacophorans), calcareous and siliceous
spicules of sponges and probably soft corals, arthropod carapaces, calcareous cups of sponge-like
archaeocyathans, shells of brachiopods and brachiopod-like animals, as well as various tooth-like
objects
- hyolithids (Cambrian - Permian) sometimes classified as molluscs but often with opercula and
"arm-like" structures
PALEO LECTURE, PAGE 32
G. The Causes of Metazoan Diversification (the "Cambrian Explosion")
1. Environmental Factors
a. end of late Precambrian (Varanginian) glaciation
b. development of extensive continental shelf areas and epicontinental seas
c. Oxygen increases to 6-10% of present atmospheric levels; development of the ozone layer
allows organisms to leave restricted environments
2. Biological Factors
a. microorganisms increase in number and therefore with increase in filter-feeders
b. organisms create habitats for other organisms
c. secretion of skeletons
- development of hard skeletons of organic (scleroproteins and polysaccharids) or biomineralized
(silica, carbonate, apatite) materials
- for protection, support above the substrate, muscle attachment, guides for feeding currents,
supplies of calcium and phosphate nutrients
- calcium carbonate skeletons could not be secreted until oxygen reached approximately 10% of
modern levels (about 2% total atmospheric gases)
H. Characteristics and the Classification of the Modern Metazoans
1. Presence/Absence of Internal Body Cavities
a. Acoelomate Organisms
- do not have coeloms (cavities) for housing organs
- include Protozoa, Porifera, Cnidaria, Platyhelminthes (flatworms)
- probably evolved from colonial flagellate protozoans
b. Coelomate Organisms
- with coeloms; higher invertebrates and chordates; molluscs with poorly developed coeloms
- echinoderms, annelids, arthropods, chordates with well-developed coelomic cavities
b1. Pseudocoelomates
- space between the gut (endoderm) and external covering (ectoderm) is not filled with
mesodermal cells; includes the wormlike rotifers and nematodes (no fossil record); coelom is to
make the body rigid for muscle contraction
b2. Schizocoelomates
PALEO LECTURE, PAGE 33
- coelom forms first as a split in the mesodermal tissue (= schizocoel); characteristic of annelids
and arthropods
b3. Enterocoelomates
- coelom forms when pouches from the gut extend into the mesodermal cells and are "pinched
off" (= enterocoels); characteristic of echinoderms and chordates
- schizocoelomates and enterocoelomates originated coelom for metabolic exchanges
2. Bilaterians (the Bilateria)
- organisms with a bilateral symmetry
- include most phyla of metazoans, except sponges and cnidarians
3. Metamerism
- segmentation of organisms
- formed due to need for muscular contractions in crawling, burrowing, swimming, etc.
a. Metameric segmentation
- divides entire body; is characteristic of annelids and arthropods
b. Oligomeric segmentation
- with body divided into three parts; characteristic of most other metazoans
4. Development of the Embryonic Mouth
a. Protostomes
- invagination ("pushing in") of embryo becomes the mouth; includes molluscs, annelids and
arthropods
b. Deuterostomes
- invagination of embryo becomes the anus; includes echinoderms and chordates; echinoderms
probably developed from tube-dwelling worms
- chordates probably developed from free swimming "larval" echinoderm-like forms;
development of notochord as an "anti-telescoping" device for swimming
5. Lophophorates
- possess a lophophore (comblike organ used for filter-feeding); include bryozoans and
brachiopods
VI. A Variety of Protists
A. Kingdom Protista/Protoctista
- Unicell or unicell-colonial organisms; eucaryotic cells (with organelles, membrane-bound
nucleus, etc.); Range = Precambrian to Recent
PALEO LECTURE, PAGE 34
A common classification for protists is as follows:
Kingdom Protista
Subkingdom Protozoa
Phylum Sarcomastigophora
Subphylum Sarcodina
Superclass Rhizopoda
Class Granuloreticulosa
Order Foraminiferida - foraminiferans ("forams")
Superclass Actinopodea
Class Radiolaria - radiolarians ("rads")
*Subkingdom Algae
Division Pyrrhophyta
Class Dinophyceae - dinoflagellates, ebidians (?)
?Class Incertae Sedis (uncertain taxonomic position) = acritarchs
Division Haptophyta
Class Coccolithophyceae - calcareous nannoplankton
Division Chrysophyta
**Class Bacillariophyceae (Diatomaceae) - diatoms
Class Chrysophyceae - silicoflagellates, archaeomonads (?)
Class Xanthiophyceae
Division Rhodophyta - red algae
Division Chlorophyta - green algae
Division Phaeophyta - brown algae
* Note: Subkingdom Algae is often placed within the Kingdom Plantae. **Diatoms are often
placed in a separate Division (as in your lab).
B. Division Rhodophyta
- red algae
1. ?Phylloid Algae - leaf-like; formed small carbonate banks in Carboniferous seas
2. Superfamily Corallinaceae (Late Paleozoic? Jurassic-Recent) - coralline algae; most
important rhodophytes in modern oceans; skeletal tissue forms two-layered cellular structure
C. Division Chlorophyta
- green algae; ancestral to land plants
- codiacean algae (Jurassic-Recent) with tiny aragonite spicules; important in formation of
carbonate sediments in modern tropical oceans
- receptaculitids (Ordovician-Permian) with sac-like form; often termed "sunflower fossils"; the
classification of this enigmatic taxon is controversial, with some scientists placing them within
the "pleosponges" (kin to archaeocyathans)
D. Division Pyrrhophyta/Dinoflagellata
- dinoflagellates; important index fossils
PALEO LECTURE, PAGE 35
1. Morphology
- during "resting stage" shell differentiated into two layers [outer layer (theca) composed of
cellulose-like substance; inner layer (test or cyst) made of tough, resistant easily-fossilized
organic substance]
2. Morphologic types of Dinoflagellates
- Hystricospheres (Jurassic-Recent) with long spines (processes; i.e., chorate cysts); usually
found in open marine environments
- Proximate Tests with spines short or absent; most often found in near-shore environments
3. Ecology/Paleoecology
- most marine planktonic; some benthonic; others freshwater, symbiotic (zooxanthellae of coral
reefs), or parasitic
- produce "red tide" due to production of "paralytic shellfish poison"; some luminescent
E. Division Bacillariophyta
- diatoms
1. Morphology
- pillbox-like siliceous skeleton (frustule); epitheca (larger valve) overlaps the hypotheca
2. Morphological types of Diatoms
- centric diatoms with radial symmetry
- pennate diatoms bilaterally symmetrical and with a raphe (longitudinal slit in the valve along its
apical axis)
3. Ecology/Paleoecology
- wide variety of environments; freshwater, marine; planktonic or benthonic
- asexual reproduction with reduction in size of tests (returns to normal size during sexual stages)
F. Division Haptophyta
- calcareous nannoplankton or coccoliths; Early Jurassic-Recent
- with skeleton consisting of minute calcareous shields (usually fall apart after death of algae)
- coccoliths (individual elliptical to circular shields) 1 to 15 microns in diameter
- asteroliths (discoasters) often star-shaped
G. Phylum Protozoa
- single cells or colonial aggregates or cells without differentiation of function; reproduce mostly
asexually; move by means of pseudopodia or cilia
Subphylum Sarcodina = non-flagellate, with pseudopodia
1. Order Foraminiferida
a. Foraminiferan Biology
PALEO LECTURE, PAGE 36
a1. Nutrition
- Pseudopodia = flowing protoplasmic extensions; moves particles in or out of inner protoplasm
in conveyer-like motion (Streaming)
- Some benthic and planktonic forams cohabit with symbiotic algae (Zooxanthellae);
photosynthesis provides food for forams
a2. Movement
- Benthic forams - sessile or vagile (move by pseudopodia)
- Planktonic forams - several migrate through water column into surface zone (probably by
changes in gas content of protoplasm)
a3. Reproduction
- Heterophasic - with 2 types (phases) of reproduction (= alternation of generations); only in
benthics
- Schizogony = asexual phase; with larger initial chamber (proloculus) = Macrospheric
Generation)
- Gamogony = sexual phase; smaller proloculus (= Microspheric generation)
b. Foraminiferan Test Morphology
Test (the "shell") - consists of a secreted or agglutinated covering
b1. Wall Structure - cement grains, mineralize carbonates or combination of these two
Agglutinated Wall Structure - oldest geologically, cement particles on layer of tectin (organic
compound)
Microgranular wall structure = evolved in Paleozoic; microganular calcite gives test a "sugary"
appearance
Calcareous Walls
Calcareous hyaline = calcite or aragonite; with minute perforations in the test wall
Radial hyaline = calcite or aragonite arranged with "C" axis normal to test surface
Granular hyaline = crystallites randomly oriented
Calcareous porcelaneous = shiny, smooth appearance of test due to orientation of submicroscopic
calcite grains (randomly arranged or brick-like)
b2. Chambers = test cavity and its surrounding wall
- may possess one or more chambers
- Chamber arrangement = uniserial (1 row of chambers); biserial (2 rows of chambers added in
each whorl); triserial [3 (or 2 and 3) chambers added in each whorl]
- Degree of curvature of rows of chambers = rectilinear (straight series); arcuate (curved row of
chambers); planispiral (spiral lies in single plane); trochospiral (spiral does not lie in single plane
but with an axis of coiling); streptospiral (trochospiral coiling in several planes of coiling)
PALEO LECTURE, PAGE 37
b3. Degree of involution = involute (majority of previous coils hidden) and evolute (majority
of previous coils visible)
b4. Coiled Test morphology = spiral side (side showing traces of coil); umbilical side
(opposite side of spiral, may have umbilicus = axial space between inner margins of chambers
belonging to same coil)
b5. Apertures = primary openings of the test to the outside environment
b6. Pores = round, slit-like or irregular openings approximately 5-6 mm in size; found in
agglutinated and hyaline forams
b7. Ornamentation = protrusions; thickening or sharpening of chamber peripheries to form
keels; also ribs, ridges, striae, furrows, spines
c. Major Morphological Groups of Foraminiferans
- approximately 100 families; 1200 genera; 27,000 species of forams
- over 35 classification schemes have been used
c1. Basis of classification (most important are grouped first)
1) wall composition and microstructure
2) chamber arrangement and septal addition
3) aperture characters and modifications
4) chamber form
5) life habits and habitats
6) protoplasmic characteristics
7) ontogenetic changes
8) reproductive processes
9) Geologic Ranges
c2. Outline of Classification (Major Groups)
Suborder Allogromiina = single-chambered, tubular, round, or flask-shaped; test pseudochitinous
(tectinous), agglutinated material in some genera (Paleozoic-Recent)
Suborder Textulariina = arenaceous or agglutinated tests (Paleozoic-Recent)
PALEO LECTURE, PAGE 38
Suborder Fusulinina = primitive forams; calcareous microgranular tests which lack a
crystallographic orientation (Pennsylvanian-Permian)
Suborder Miliolina = calcareous, porcelaneous tests (Triassic-Recent)
Suborder Rotaliina = hyaline perforate calcareous test (Triassic-Recent)
d. Fusulinid Foraminifera
d1. Morphology
- small to very large (up to 10 cm); often look like "wheat grains"
- studied by means of axial (most important), sagittal and tangential thin sections
- evolutionary trends are increase in size of the initial chamber (proloculus); increase in overall
size; increase in complexity of the wall structure; increase in intensity of the septal fluting (i.e,
increase in corregations of the septa, which divide the test into chambers)
d2. Biostratigraphy
- Fusulinid Range = Lower Pennsylvanian - Upper Permian
- In Upper Paleozoic with 10 fusulinid biostratigraphic assemblage zones
d3. Paleoecology
- most were marine, benthonic and associated with relatively shallow, well aerated, carbonate
depositional environments; often associated with corals and algae
e. Paleozoic Agglutinated Foraminiferans
- Suborders Allogromiina and Textulariina with approximately 67 genera in the Paleozoic
- typically found in silty shales and/or fine-grained shaly sandstones and fine-grained mud-rich
limestones
- Carboniferous with 14 biozones based on agglutinated and microgranular forams
f. Giant Foraminiferans
- important throughout the Cenozoic in tropical seas; typically planispirally-coiled; Ex. =
Nummulites (Camerina)
g. Planktonic Foraminiferans
- Jurassic- Recent
- important sediment-formers and important in Mesozoic and Cenozoic biostratigraphy
- with ornamentation (spines, keels) or bulbous chambers to assist in flotation
2. Phylum Actinopoda (Radiolaria)
- radiolarians
a. Morphology
- shells of silica or strontium sulfate
PALEO LECTURE, PAGE 39
b. Classification
- divided into four classes on the basis of the construction of the nucleus and the shape and
composition of the shell (only Classes Spumellariina and Nassellariina important; both with
shells of opaline silica)
- spumellarians with spherical symmetry; nasellarians with tripod-shape or ring-like, or shells
elongate, multichambered and latticed
c. Ecology/Paleoecology
- exclusively marine and planktonic; live at all oceanic depths and with cosmopolitan (worldwide) distibution
VII. Sponges, True and Problematical
A. Phylum Archaeocyatha
- sometimes placed within the sponges
1. Biology
a. Calcareous skeleton, usually conical
- usually double-walled with space (intervallum) in between (some lack inner wall); vertical
partitions (septa) and horizontal partitions (tabula) divide the intervallum into loculi
- with central cavity; skeleton perforated by large and small pores
b. Reproduction by asexual budding and fission; also sexual? (probably with planktonic larvae)
2. Paleoecology
- shallow marine, sessile benthonic (as adults), filter-feeders
- lived in aggregates or communities dominated by calcareous algae or algal-like organisms of
uncertain affinities; often found in reef-like carbonate buildups
3. Biostratigraphy
Range: Lower to Upper Cambrian (in North America only Lower Cambrian types are known)
B. Phylum Porifera
- sponges
1. Biology
a. Soft Parts
- No internal organs, nervous tissue, circulatory or digestive system (No mouth or anus)
- Dermal pores = external apertures which bring in food and oxygen; lined with collared
flagellate cells (choanocytes) that produce water currents and trap food
- Cloaca (spongocoel) = central cavity
PALEO LECTURE, PAGE 40
- Osculum = lets out water from the spongocoel
b. Reproduction
Asexual - by budding or branching
Sexual - most important; spherical larva (amphiblastula) attach themselves to substrate and give
rise to a sponge
2. Skeleton
- simple types with no skeleton
a. Spongin = horny organic substance; not found fossilized
b. Spicules
- interlocking minute siliceous (opaline silica) or calcareous (calcite) needles, hooks or plates
embedded in the tissues
- with Two sizes of spicules = Megascleres (larger spicules up to 0.3mm long; forms main mass
of skeleton); Microscleres (smaller spicules 0.01-0.1mm; serve as reinforcement, especially
around pores)
- Kinds of spicules include Monaxon spicules (with single axis; calcareous or siliceous); Triaxon
spicules (siliceous; 3 axes); Tetraxon spicules (4 axes not in the same plane); Polyaxon spicules
(with several equal rays diverging from a point; siliceous) and Desmas (siliceous spicule; with no
ordered arrangement)
3. Types of body structure
a. Ascon (asconoid) type
- simplest; vaselike; water enters body by means of dermal pores and water exits through large
rounded vent (osculum) at top of sponge
b. Sycon (syconoid) type
- with infolded wall (for strength and increase digestive area)
c. Leucon (Leuconoid) type
- chambers become subdivided and concentrated; typically lack a wide central chamber
d. Rhagon (rhagonoid) type
- most advanced sponge; derived leucon type in which flagellated cells are confined to spherical
chambers buried deeply in body wall
4. Sponge Classification
The following is a typical sponge classification:
Phylum Porifera
Subphylum Symplasma
PALEO LECTURE, PAGE 41
Class Hexactinellida
Subphylum Cellularia
Class Calcarea
Order Pharetronida
?Order Heteractinida
Other minor orders
Class Sclerospongea*
?Order Stromatoporoidea*
?Order Chaetetida*
?Class Archaeocyathida* (see above)
Class Demospongia
Order Lithistida
Order Sphinctozoa
Order Keratosa
Other minor orders
*Note: The Sclerospongea (including Stromatoporoidea), Chaetetida and Archaeocyathida are
often referred to the Demospongia. Archaeocyathans, as noted above, are often classified as a
separate phylum (as followed herein). Sclerosponges, chaetetids and stromatoporoids are often
classified separately (as in your book). Receptacultids and Archaeocyathids are often classified
together as "pleosponges", although I have tentatively classified receptaculitids as algae!
5. Class Demospongea
- includes approximately 95% modern marine sponges
a. Morphology - may lack spicules or have skeletons of spongin or silica or spongin + silica;
(often siliceous spicules with rays meeting at 60 or 120° angles); body structure: rhagon
b. Fossil Representatives - Lithistids most important Paleozoic demosponges; skeleton of
siliceous desmas
c. Ecology/Paleoecology - includes all of known freshwater forms; approximately 95% of
modern marine sponges; marine environments range from warm, shallow subtidal, high energy to
quiet, cold oceanic deeps
d. Biostratigraphy - Middle Cambrian to Recent; record is typically discontinuous, localized
and represents a poor sampling of sponge diversity (all sponges of little use biostratigraphically)
6. Class Calcarea (Calcispongea)
a. Morphology - discrete or united calcareous spicules; spicule types = monaxon, triaxons
(most common), tetraxons; body structure = ascon, sycon, rhagon
b. Fossil Representatives
- "Pharetronids" (probably a polyphyletic group) are Calcarea with rigid skeletons (Lower
PALEO LECTURE, PAGE 42
Permian - Recent) and represent most abundant group
- Order Heteractinida with polyaxons of octactine (most abundant), sexiradiate and polyactine
morphology (see lab manual); spicules are solid and form discrete units; Middle Cambrian to
Permian; Ex. = Astraeospongium
c. Ecology/Paleoecology - mostly shallow marine
d. Biostratigraphy - Range = Precambrian?; Cambrian-Recent (also see above for individual
groups)
7. Class Hexactinellida
- include "glass sponges"
a. Morphology - tubular bodies; six-rayed discrete or unified siliceous spicules; rays developed
along three mutually perpendicular axes; microscleres always present and either hexasters (small
hexactinal spicules, often flower-like ends) or birotulates (small monaxons with umbrella-like
ends); axial canal of megascleres is square in cross-section; body structure: Rhagon
b. Ecology/Paleoecology - Paleozoic types mostly lived on organic-rich, soft mud bottoms,
probably in quiet water ; Mesozoic forms (especially Cretaceous) often in chalk facies; Cenozoic
forms little-known; modern types mostly in upper bathyal zone (200-2000 m water depth)
c. Biostratigraphy - Range: Lower Cambrian-Recent
8. Class Sclerospongiae
a. Morphology - with a three-layered skeleton (base of crystalline and aspicular calcite or
aragonite; middle of living tissues; upper with siliceous spicules and collagenous fibers);
probably related to demosponges (and often classified with them)
b. Fossils - may include the stromatoporoids and chaetetids (see below)
c. Ecology - modern types often in shaded crevices, caves and tunnels on coral reefs
d. Biostratigraphy - Cambrian to Recent (if stromatoporoids are included)
e. Order Stromatoporoida
e1. Morphology
- calcareous skeleton (coenosteum) with horizontal (plates, laminae) and vertical (pillar)
structures; outwardly-branching canals may be present; growth = laminar (sheet-like), massive,
cylindrical, dendroid; with small pores present in laminae or pillars and laminae
e2. Paleoecology
- typically lived in clear warm, shallow water; occured on reefs (reef-builders) or as commensals
PALEO LECTURE, PAGE 43
of corals in quiet water a few feet deep
Biotic association = most often found with tabulate corals, also bryozoa, algae, crinoids,
brachiopods
e3. Biostratigraphy
- Cambrian through Cretaceous (abundant in carbonate environments from Middle Ordovician Late Devonian)
-----------f. Order Chaetetida
f1. Morphology = skeleton composed of numerous distinct, narrow tubes (calicles); walls of
tubes joined; calicles small (0.1-0.6 mm), divided by septa (vertical partitions) and tabulae
(horizontal partitions)
f2. Paleoecology = firm substrate, most in shallow, warm, sunlit waters; often associated with
algae and may form bioherms or reefs
f3. Biostratigraphy = Ordovician to Miocene (locally abundant in Lower to Middle
Pennsylvanian)
VIII. Simple Coelenterates: the Cnidarians
Phylum Cnidaria - well developed body tissues but simply organized; includes corals, sea
anemonies, jellyfish
A. General Characteristics
1. Multicellular, most with tentacles (food-grasping projections) which surround mouth
2. radial symmetry about an axis between the mouth (oral pole) and base (aboral pole)
3. Tissue grade of construction; body wall and tentacles with ectoderm and endoderm separated
by mesoglea (connective tissue)
4. With central cavity (coelenteron/enteron) joining mouth (intake and ejection of food); central
cavity often divided by radial folds and partitions
a. Systems present = digestive, muscular, nervous, reproductive, elementary sensory
b. Systems lacking = respiratory, excretory, circulatory
5. Nematocysts (stinging capsules) present for use in defense and food capture
PALEO LECTURE, PAGE 44
6. Asexual budding producing solitary polyps or polypoid colonies; sexual reproduction
produces ciliated larvae (planula) which attach to bottom and form a polyp
7. With two stages (polymorphism) - a free-swimming medusoid stage and fixed polyp stage; in
Hydrozoa both stages may occur or may have medusoid stage only
8. Some with endoskeletons, some exoskeletons which may be calcite or aragonite (hydrozoans,
anthozoans) or chitin and calcium phosphatic (conulatids); very rarely horn-like fossils of
hydroids and are more like anthozoans
9. Chiefly marine
B. Class Hydrozoa
- includes Hydra (fresh-water) and many marine types (staghorn coral and siphonophores)
1. Characteristics
- solitary or colonial; enteron lacks gullet (leads from mouth to gastrovascular cavity); most with
chitinous skeletons (some calcareous); mostly marine (few fresh-water); often polyp and
medusoid generations alternate
2. Range: Late Proterozoic? to Recent - not important as fossils
C. Class Scyphozoa
1. Biology
- solitary; radial symmetry; Medusa stage dominant; Polyp (attached forms) much reduced,
highly modified or lost; coelenteron in some types divided by mesenteries (radially-arranged
walls of tissue); living forms with sexes separate (male sperm, female eggs)
2. Classification
a. Subclass Scyphomedusae
- jellyfish (true medusae = free-floating forms); nektonic; hard parts lacking (gelatinous bell and
tentacles); marine only; Range: Upper Proterozoic? - Recent
b. ?Subclass Conulariida (conulatids, conularids)
- formerly referred to the worms, molluscs, coelentrates and hemichordates; Skeleton chitin and
calcium phospate; elongate pyramidal form; attached by apex of pyramid or free-swimming;
tentacles present
- Paleoecology = Marine sessile benthonic or nektonic; found in all lithologies but mostly in dark
carbonaceous shale
- Biostratigraphic Range: Middle Cambrian-Early Triassic
D. Class Anthozoa
PALEO LECTURE, PAGE 45
- includes sea anemones, corals, sea fans, sea pens, sea feathers
1. Biology
- solitary or colonial; polyps only (no medusae); oral end bears tentacles; gullet present (leads
from mouth to gastrovascular cavity); coelenteron partitioned by mesenteries (radially arranged
wall of tissue; will have mineralized septa of aragonite within and between mesenteries in most
groups)
2. Classification
- classified on whether the mesenteries are paired or not; 2 subclasses but only important one is
the Zoantharia
Subclass Zoantharia
- includes corals, sea anemones, seafans, sea pens, tabulate and rugose corals
- classification based on arrangement and development of mesenteries and presence or absence of
a skeleton
- Characteristics = solitary or colonial; calcareous exoskeleton; paired (coupled) mesenteries
a. Order Rugosa (Tetracoralla)
- Biology = solitary or colonial; calcareous skeleton (corallite) with epitheca (calcareous wall),
septa (radial plate from wall to axis of corallite) and typically with tabulae (transverse partitions)
and dissepiments (small curved plates forming a vesicle); 6 primary septa (protosepta;
correspond to 6 paired mesenteries); secondary septa develop in 4 of 6 interseptal spaces
[therefore 4-fold (biradial) symmetry and called Tetracoralla)
- Paleoecology = marine sessile benthonic; most in shallow water; warm, well-oxygenated water
with normal salinity; best in areas of slow deposition (limestone beds rather than shale or
sandstone); Solitary types with small attachment and often knocked over (twisted skeletons);
often found on reefs along with tabulate corals, stromatoporoids, brachiopods and bryozoans
- Biostratigraphic Range: Ordovician-Permian; Rugose biozones in Mississippian through
Permian in North America, Britain and Australia and to a lesser extent in Ordovician-Silurian
b. Order Tabulata
- Biology = colonial; calcareous skeleton with epitheca (outer wall) and tabulae (transverse
partitions); septa (radial partitions) typically small or absent; when present most common number
is 12
- Paleoecology = reef builders in warm, shallow (less than 50m water depth), clear, welloxygenated (agitated, gently circulating) water; bottom free of silt (if silty would prevent larval
attachment)
- Biostratigraphic Range: Ordovician-Permian
c. Order Scleractinia
c1. Morphology
- septa in multiples of six (hexacorals)
PALEO LECTURE, PAGE 46
c2. Paleoecology
- most important modern reef-builders [live in symbiotic relationship with dinoflagellates
(zooxanthellae)]
- shallow water (maximum water depth fifty meters); well-oxygenated, agitated, well-circulated
water in photic zone; prefer water temperature of about 65°F; substrate relatively free from silt
accumulations
IX. "Moss Animals", or Bryozoans
Phylum Bryozoa - 4,000 living and 15,000 fossil species; live in colonies or a few individuals up
to 10cm diameter; may appear bush-like, fungiform or encrusting; often carpet-like ("mossanimals"); Sessile, most with calcareous skeleton
A. Biology
1. Soft parts
- Zooid = (individual animal) consists of polypide (soft parts) and zoarium (skeleton)
- polypide enclosed in a carbonate skeleton with opening (orifice, zooecial aperture)
- with lophophore [this links bryozoans with tubicolcous worms (Phylum Phoronida) and
Brachiopoda; all 3 probably evolved from a worm-like ancestor] = food catching organism
consisting of tentacular crown (with 8 to more than 100 tentacles) arranged in a circle around the
mouth; tentacles with cilia which produce a water current to sweep food into the mouth; food
consists of microorganisms, bacteria and organic detritus
- Mouth leads into a complete alimentary canal
- No respiratory or circulatory system
- Polymorphism = many groups with ordinary feeding individuals, some may have wierd birdhead like animals for feeding or defense, others with bristles to move food and larvae, others
with thickened walls for attachment
2. Reproduction and Life Cycle
- Colonies usually hermaphroditic (with male and female zooids; rarely colonies consist of all
males or all females)
- Larva settles to substrate in a few hours and metamorphoses into a primary zooid; Colony forms
by asexual budding of daughter zooids
3. Skeleton
- most with skeleton of CaCO3 (calcite or calcite and aragonite)
- study usually by thin sections (1 longitudinal section and 1 tangential section (perpendicular to
tubes) = especially study Wall Structure
- Types of Wall Structure include amalgamate structure = walls of adjacent tubes coalesced;
integrate structure = tube walls of zooecium distinct from other zooecium walls
- Acanthopore = slender dense-walled tube
PALEO LECTURE, PAGE 47
- Zooecium (Autopore) large tube or chamber occupied by one of main zooids
- Mesopore = tube parallel to autopores; usually smaller and more angular with numerous
diaphragms; probably occupied by specialized zooids
- Cystiphragm = calcareous plate extending from zooecial wall part-way across tube; surface
coned, convex upward and inward
- Diaphragm = calcareous plate extending transversely across width of zooecial tube; surface flat
or gently curved
- Coenosteum (coen) = vesicular or dense skeletal material between zooecia
B. Classification of Bryozoans
1. Class Stenolaemata
- zooecia cylindrical with calcified body wall; new zooecia produced in a common bud by
division of septa; marine; ovicell large; Ordovician-Recent (approximately 550 genera)
a. Order Tubuliporata (Cyclostomata) = calcareous tubular chamber with lidless circular
aperture; Early Ordovician to Recent
b. Order Cryptostomata = short calcareous tube; colony peripheral walls thick; Ordovician Permian
c. Order Cystoporata (Fistuliporids) = tubular zooecia isolated by cystose tissue; Early
Ordovician - Triassic
d. Order Fenestrata (fenestrates, fenestellids) = sheets pierced by holes; Early Ordovician Triassic
e. Order Trepostomata = long curved calcareous tube usually intersected by partitions
(immature and mature parts of colony distinct); Ordovician - Triassic
2. Class Phylactolaemata
- non-calcareous body wall, fresh water; Late Tertiary-Recent (fossil record poor)
3. Class Gymnolaemata
- most successful group of modern bryozoans; almost exclusively marine (but some freshwater)
having a circular row of tentacles surrounding the mouth; most complex forms with elaborately
calcified zooids, skeletons often with both aragonite and calcite layers; Ordovician - Recent
a. Order Ctenostomata
- zooids enclosed in a gelatinous chamber; comb-like processes close aperture when tentacles are
PALEO LECTURE, PAGE 48
retracted; fossils typically consist of chemical borings produced by soft-bodied colonies within
calcareous substrates (and often classified as trace fossils); Ordovician-Recent
b. Order Cheilostomata
- zooids enclosed in short saclike chitinous or calcareous chamber; hinged chitinous operculum
(lid) encloses aperture when tentacles are retracted; about 1000 genera, constituting most known
fossil and living species of bryozoans; Jurassic-Recent
C. Ecology/Paleoecology of Bryozoans
1. Sessile benthonic; most normal marine [a few (12 genera) are freshwater]
2. Lithology = most in calcareous rocks (limestone, calcareous shales and shelly marls); rare in
black shales, dolomites and quartzose clastic rocks
3. Biotic Association
Paleozoic = most with sessile benthonic organisms (solitary corals, articulate brachiopods,
echinoderms)
Post-Paleozoic = mostly with mollusks, sponges, octocorals
4. In both ancient and recent sediments most often found in sediments of continental shelves
and around coral reefs (often contribute to reef buildup by trapping sediments)
5. Factors controlling distribution
- generally hard substrates (attached to invertebrate shells, stones and large algae)
- water turbulence controls upper bathymetric limit; delicate, leaf-like types in calm water;
branching forms usually in lower waters and massive, encrusting types in more turbulent water
- rates of sedimentation = Bryozoa not much affected
- salinity = normal sea water (salinity = 35 o/oo)
D. Biostratigraphy of Bryozoans
- bryozoans may be useful biostratigraphically; microorganisms, widespread, rapid evolution
- Lower Paleozoic with mostly stony bryozoans (with robust branching zoaria but occur in
massive or globular colonies)
- Upper Paleozoic mostly slender branching colonies and lace-like types (fenestellids)
- during Upper Cretaceous the Cheilostomata expanded to approximately 100 genera, where they
are well-preserved within chalk deposits
- Lower Tertiary with rapid and abundant changes in morphology
- Upper Tertiary with many geographic shifts in distribution, but less origination and extinction
versus Lower Tertiary
PALEO LECTURE, PAGE 49
X. The Sturdy Brachiopods
Phylum Brachiopoda - lophophore-bearing marine coelomates; related to bryozoans and
phoronid worms; 1700 fossil and extant genera, 30,000 extinct species; approximately 260 extant
species
A. Biology
1. Soft Parts
a. Lophophore
- complex ciliated, feeding organ surrounding the mouth; consists of pair of coiled arms (brachia)
with ciliated, tentacle-like cirri
b. Mantle
- two folds of body wall that line the inner surface of the valves; outer fold secretes shell and
inner fold separates 2 cavities
c. Cavities
- Body (coelomic) cavity in posterior 1/3 of shell; main body occupies body cavity
- Mantle (brachial) cavity occupies anterior 2/3 of shell; largely occupied by lophophore
suspended between mantles
d. Systems
Digestive = articulates intestine with blind terminus (fecal pellets voided through mouth);
inarticulates with anus
- Primitive circulatory and nervous system
- Muscular = 3 sets of muscles in articulates [1 to open valve (diductor), 1 to close valve
(adductor), pedicle (muscular) attachment]; Inarticulates with 1-2 adductors (close valves), 3
pairs of oblique muscles; muscle scar morphology is important in brachiopod taxonomy
2. Reproduction and Life Cycle
- Sexes separate
- commonly with free swimming larval stage whose head attaches to bottom to form benthonic
adult form
3. Skeleton
PALEO LECTURE, PAGE 50
a. Bilaterally symmetrical (line must be drawn across valves; pelecypod with line drawn
between valves); valves in brachiopods unequal
b. Bivalved
- Dorsal (brachial) valve = contains lophophore
- Ventral (pedicle) valve = larger valve which has muscular pedicle at posterior end
- Valves hinged (articulates) or unhinged (inarticulates)
c. Morphology of articulate brachiopods:
Foramen = pedicle opening
Beak = pointed extremity of valve where shell growth begins
Commissure = junction between edges of valves
Hinge line = edge of shell where valves articulate
Cardinal extremity = lateral terminus of hinge line
Beak ridge = ridge extending from beak to cardinal extremity
Delthyrium = opening in pedicle valve adjacent to hinge line; serves for passage of pedicle
Fold = elevation (up-arch) of a valve (usually on brachial valve) along the midline
Sulcus = depression of a valve along the midline (usually on pedicle valve)
Plications (plica) = radial ridges and depressions involving entire thickness of shell
(corrugations on inner and outer surfaces)
Umbo = relatively convex portion of valve next to (anterior to) beak
Interarea = plane or curved surface between beak and hinge line on either valve
B. Brachiopod classification
1. Class Inarticulata
- shell chitinophosphatic or calcareous; shell punctate (perforated by fine tubes or pores from
interior to almost the outer surface; for respiration when valve is closed) or impunctate (solid
layers); valves never articulated by teeth and sockets; muscles and body wall hold valves
together; attachment by pedicle or no attachment; Range: Lower Cambrian-Recent
PALEO LECTURE, PAGE 51
- Major orders include Paterinida, Lingulida, Acrotretida, and Obolellida
a. Order Lingulida
- Cambrian to Recent; shells primarily composed of calcium phosphate; shells biconvex, and
oval to squarish in outline; lingulids burrow into soft sediment, where they are anchored by their
long pedicle
b. Order Acrotretida
- Cambrian to Recent; shells generally subcircular to circular, unequally biconvex, and often have
a pedicle opening; craniaceans have no pedicle and cement their ventral valve to the substrate
c. Order Obolellida
- Cambrian only; valves circular to oval; ventral valve with a pseudo-interarea and with a pedicle
opening
2. Class Articulata
- Shell calcareous, punctate (perforated by fine tubes or pores from interior to almost the outer
surface), impunctate (solid layers) or pseudopunctate (lack pores but fibrous layer with rod-like
calcite; differential weathering gives appearance of being punctate); valves articulated by hinge
teeth and sockets; Lower Cambrian-Recent
a. Order Orthida
- probably ancestral to other articulate brachiopods; generally unequally biconvex shells with
radial ribs (costae); relatively wide straight hinge lines and with interareas on both valves; shell
impunctate, rarely punctate or pseudopunctate; 2 suborders; Lower Cambrian-Upper Permian
b. Order Strophomenida
- plano-convex to concave-convex, less commonly biconvex; interareas highly variable, hinge
line typically long; pedicle opening much reduced or absent; typically pseudopunctate; Lower
Ordovician - Triassic; 4 suborders (two important)
- Suborder Strophomenidina (Strophomenacea) = interarea well developed on one or both valves;
pedicle foramen very minute or lacking; Lower Ordovician - Triassic
- Suborder Productidina (Productacea) - interareas reduced or lacking, spines distributed over
shell surface; Devonian - Permian
c. Order Pentamerida
- probably evolved from the Orthida; with strongly biconvex valves that are smooth or finely
costate; with robust pedicle spondylium (curved plate in midline of beak on pedicle valve for
muscle attachment); open delthyrium (opening in pedicle valve adjacent to hinge line; not
covered by a deltidium); impunctate shell; interareas commonly small; hinge line short or
moderately long; 2 orders; Middle Cambrian-Upper Devonian
d. Order Rhynchonellida
PALEO LECTURE, PAGE 52
- probably evolved from pentamerids; shell typically biconvex; interareas, pedicle and hinge
length highly variable; punctate or impunctate; spiral brachidium; Mid Ordovician-Recent; 3
Suborders (some say superfamilies)
e. Order Spiriferida
- shell typically biconvex; interareas, pedicle and hinge length highly variable; punctate or
impunctate; spiral brachidium "points" toward cardinal extremities; Mid-Ordovician-Jurassic; 4
Suborders
- Suborder Spiriferidina (Spiriferacea) = impunctate shells, long hinge lines; surfaces marked by
ribs (costae) and plications (internal and external corrugations); Middle Silurian - Early Jurassic
f. Order Terebratulida
- most abundant modern brachiopods; typically biconvex shells with short hinge line; shell
surface smooth or finely costate; interarea on pedicle valve only; punctate; functional pedicle;
complex looped brachidium (calcareous support for lophophore); Range: Lower DevonianRecent
C. Ecology of Brachiopods
1. Exclusively marine, benthonic epifaunal and gregarious
2. Food = diatoms and dinoflagellates (the #1 and #2 primary producers in modern seas)
3. Water depth = mostly shallow, continental shelf forms
4. Distribution = cosmopolitan - from Arctic to Antarctic
5. Salinity = typically normal marine but modern terebratulids and lingulids can survive lower
salinities
6. Substrate - may prefer hard substrates
D. Paleoecology of Brachiopods
1. Paleobathymetry
- water depth
- Paleozoic = essentially all shallow-water forms; Cambrian/Ordovician articulates and
inarticulates found mostly in sandy and shelly facies indicative of littoral zone; Many associated
with reef facies (Ex. = Permian Delaware Basin, Texas); Productids lived in the shallow basin, a
few on the shelf; a few associated with graptolites were probably pelagic (attached to floating
seaweeds)
- Mesozoic-Tertiary = Essentially all deeper water forms originated during Mesozoic - post-
PALEO LECTURE, PAGE 53
Mesozoic
- Essentially all inarticulates at shallow depth (most less than 60 feet)
2. Biotic Association
- Paleozoic with very abundant brachiopods and probably very important link in food chain
- some with possibly symbiotic relationships with corals (?)
3. Attachment
- Fossil brachiopods variously attached pedicles; some first attached by pedicle but later pedicle
atrophies and leaves shell free on substrate (Strophomenida); attached by cementation to hard
substrates; originally cemented but later free on substrate (commonly with concave-convex shells
such as productids; anchored or attached by spines); some types with byssus-like threads
attaching to substrate
E. Biostratigraphy of Brachiopods
- Cambrian dominated by trilobites and inarticulate brachiopods
- three maxima for numbers of genera - Ordovician, Devonian (most diversity) and Permian
- three groups dominate Paleozoic = orthids, strophomenids, spiriferids
- Ordovician with marine transgression and opening of new niches
- Devonian - brachs in all marine environments; many important index fossils
- Mississippian - Pennsylvanian with decline (due to abundant coal swamp environments and
cooling seas?)
- Tremendous decrease in numbers in Late Permian - Early Mesozoic
- Few Mesozoic forms (mostly rhynchonellids and terebratulids; Terebratuloids found throughout
Tertiary worldwide)
XI. Worms, Burrows, Trails, and Other Problematica
A. Worms of Various Phyla
- a number of largely unrelated forms (the "Vermes" of older classifications) have been
considered as "worms"; these include the priapulid worms (Nemertea), flatworms
(Platyhelminthes), peanut worms (Siphunculoida), roundworms (Nematoda or
Nemathelminthes), horsehair worms (Nematomorpha), and segmented worms (Annelida; the
only phylum commonly preserved as fossils)
PALEO LECTURE, PAGE 54
1. Phylum Annelida
- segmented worms, including earthworms (Oligochaeta), leeches (Hirudinea) and marine
bristleworms (Polychaeta)
a. Annelid Biology
- composed of many ringlike, similar segments, and with segmentation of internal structures
including nerves, muscles, circulatory, excretory and reproductive organs
b. Annelid Paleontology
- members of a few polychaete orders possess pharyngeal jaws (scolecodonts), including a
ventral pair (mandibles) for chewing, a series of asymmetrical paired maxillae for manipulating
food, and a basal pair (carriers) that support the posterior maxillae; some polychaetes secrete
agglutinated tubes by cementing sand grains, shell fragments or debris with mucus, or secrete
calcareous shells that are commonly preserved as fossils (Exs. = Spirorbis, Serpula); about 150
genera of polychaetes known; Proterozoic?, Cambrian to Recent
B. Ichnology
- study of trace fossils (ichnofossils, lebensspuren; tracks, trails, and burrows of organisms)
- may be described by means of descriptive-genetic classification, Ethological classification or by
morphology
- Ichnogenus - morphological type of a trace fossil (reflects environment rather than the creator)
- Ichnofacies - correlation between depositional environments and trace fossil assemblages
1. Trace fossils useful due to:
a. long time range
b. narrow facies range
c. no secondary transport (therefore good indicators of original sedimentological conditions)
d. prefer clastic sediments
- trace fossils are often formed in environments hostile to the preservation of body fossils, such
as beach sands and deep marine shales
e. not usually affected by diagenesis
2. Sedimentological uses of trace fossils
a. Rate of deposition
- Slow, continuous deposition typically with complete bioturbation
- Rapid, continuous deposition with no trace fossils except escape structures
b. Substrate consistency
- Silty and muddy substrates with deposit feeders
PALEO LECTURE, PAGE 55
- Clean, well sorted (high energy) sediments with specialized suspension feeders
- Soft substrates- soft bodied forms
- Firm substrates-crustaceans (with claw marks)
- Hard substrates- mechanical or chemical borers
c. Paleobathymetry- determining ancient water depth; the major use of trace fossils
Ichnofacies Include:
c1. Scoyenia Ichnofacies
- curvilinear rods with wrinkled or striated surfaces; horizontal to vertical; insect burrows?;
found in nonmarine environments
c2. Trypanites Ichnofacies
- borings into fully consolidated substrates on rocky coasts, in beach rock, reefs and hardgrounds.
c3. Skolithos Inchofacies
- intertidal environments (zone of suspension feeders); vertical "pipe rocks" in sandy sediments
c4. Glossifungites Ichnofacies
- ear-shaped spreite developed on intertidal firm mud bodies
c5. Cruziana Ichnofacies
- crawling traces (Cruziana) or inclined spreite-filled U-shaped burrows (Rhizocorallium)
developed on the continental shelf (zone of generalized sediment feeders)
c6. Zoophycos Ichnofacies
- large spreite- filled feeding loops found below wave base and above turbidite zone (zone of
churners; also with worm-like Phycosiphon in muds)
c7. Nereites Ichnofacies
- zone of systematic grazers and farmers with densely meandering horizontal feeding traces
(Nereites) or leaf-like traces (Oldhamia); zone of systematic grazers and farmers
3. Descriptive-Genetic Classification of Trace Fossils
a. Tracks and Trails
a1. Track - impression left in underlying sediment by a podium or foot
a2. Trackway - succession of tracks indicating directed locomotion
a3. Trail - directed locomotion produces a superficial groove made by contact of the animal's
body OR continuous subsurface structure made by a mobile endobenthic/infaunal organism
PALEO LECTURE, PAGE 56
b. Burrows and Borings
b1. Boring - excavation made in consolidated or firm substrates (e.g., shell, rock, bone, wood,
etc.)
b2. Burrow - excavation in loose, unconsolidated sediment
b3. Burrow or Boring System - highly ramified or interconnected burrows or borings, typically
involving shafts and tunnels
b4. Burrow Casts - sediments infilling a burrow
c. Bioturbation Texture
- texture or fabric due to disturbance of sediments by organisms (bioturbation); often consists of
dense, contorted, truncated or interpenetrating burrows or other traces, few of which remain
distinct morphologically
d. Spreite
- blade-like to sinuous, U-shaped, or spiraled structure consisting of sets or cosets of closely
juxtaposed, repetitious parallel or concentric feeding or dwelling burrows or grazing traces
4. Ethological Classification of Trace Fossils
a. Cubichnia
- resting traces; often shallow depressions made by animals settling or digging into the substrate
b. Repichnia
- crawling traces; trackways, superficial trails, etc.
c. Pascichnia
- grazing traces; grooves, pits, and furrows due to mobile deposit feeders ("strip-miners") at or
near the surface of the substrate
d. Fodinichnia
- feeding structures; temporary burrows due to deposit feeders ("underground miners"); often
form single, branched or unbranched shafts or U-shaped burrows OR spreite structures
e. Domichnia
- dwelling structures; burrows or tubes representing "permanent" domiciles, mostly of suspension
feeders; form simple, bifurcated or U-shaped structures perpendicular or inclined at angles to the
bedding OR branching burrow systems
f. Fugichnia (Escape Structures)
- substrate degradation or aggradation results in displacement of animals upward or downward
with respect to the original substrate surface; often forms vertically repetitive traces
PALEO LECTURE, PAGE 57
XII. Animals in Three Parts: the Trilobites
A. Phylum Arthropoda
1. Biology
a. Segmented exoskeleton (somites, metameres); paired jointed legs on most segments;
bilaterally symmetrical; body consists of two or more distinct regions, termed Tagma (most
differentiated into head, thorax and abdomen)
b. External skeleton (Exoskeleton) chitinous and jointed
- to increase size the exoskeleton is shed and replaced (this process is termed molting, or ecdysis)
c. Body Systems:
Nervous = highly organized
Sensory Organs = many with ocelli (compound eyes); organs for taste, smell and touch, "hearing"
(antennae and antennules = sensory bristles)
Digestive = well-developed; mouth on underside of head
Respiratory = subaqueous with gills (on limbs or confined to special gill chambers); air-breathers
with branching tubular processes (tracheae)
Circulatory = heart on dorsal side, with arteries but no veins
d. Reproduction and Ontogeny
- sexes usually separate, fertilization usually internal; after hatching pronounced changes in body
form (metamorphism) occur in many types
2. Classification
- There is much diversity in the classification of arthropods. Some authors consider the
Arthropoda as a superphylum that is subdivided into the Phylum Unirama (Classes Onychophora,
Myriapoda and Insecta), Phylum Chelicerata (Classes Xiphosura, Eurypterida, Scorpionida and
Arachnida), Phylum Crustacea (Classes Branchiopoda, Cirripedia, Malacostraca and Ostracoda)
and Phylum Trilobitomorpha (Classes Trilobita and Trilobitoidea). I have chosen a classification
system that is a bit more conservative and traditional. The numbers of described fossil genera are
given (in parentheses) and the geologic ranges of each taxon given.
Phylum Arthropoda
Superclass Trilobitomorpha: Proterozoic(?); Cambrian-Permian
PALEO LECTURE, PAGE 58
Class Trilobita (1401); Cambrian-Permian
Class(es) Uncertain including "Trilobitoidea" (16); Proterozoic(?);
Cambrian-Devonian
Superclass Crustacea: Proterozoic(?); Cambrian-Holocene
Class Brachiopoda (119); Proterozoic(?); Cambrian-Holocene
Class Malacostraca (586); Cambrian-Holocene
Class Ostracoda (1900); Cambrian-Holocene
Class Cirripedia (107); Silurian-Holocene
Class Euthycarcinoidea (2); Triassic
Class Copepoda (2); Miocene-Holocene
Class Cephalocarida (1); Camprian-Holocene
Class Mystacocarida; Holocene
Class Brachiura; Holocene
Superclass Chelicerata: Cambrian-Holocene
Class Merostomata (89); Cambrian-Holocene
Class Arachnida (289); Silurian-Holocene
Superclass Myriapoda: Silurian-Holocene
Class Archipolypoda (8); Silurian-Pennsylvanian
Class Arthropleurida (1); Pennsylvanian
Class Diplopoda (23); Pennsylvanian-Holocene
Class Chilopoda (5); Cretaceous-Holocene
Class Symphyla (1); Oligocene-Holocene
Class Pauropoda; Holocene
Superclass Hexapoda: Devonian-Holocene
Class Collembola (25); Devonian-Holocene
Class Insecta (approximately 5,000); Pennsylvanian-Holocene
Class Protura; Holocene
Class Diplura (2); Tertiary-Holocene
Superclass Onychophora: Cambrian-Holocene
Class(es) uncertain (2); Cambrian-Holocene
Superclass Pentastomida: Holocene
Class Linguatulida; Holocene
Superclass Tardigrada: Holocene
Class Eutardigrada; Holocene
Class Heterotardigrada; Holocene
Superclass Pycnogonida: Devonian-Holocene
Class Pantopoda (1); Devonian-Holocene
In this section I will review the characters of the major superclasses (or whatever they are) of
paleontological importance.
B. Superclass Trilobitomorpha
- aquatic arthropods with antennae; no appendages specialized as mouthparts; Geologic Range:
Cambrian - Permian
1. Classes Uncertain
PALEO LECTURE, PAGE 59
– the taxonomy of Cambrian arthropod-like fossils is very confused; in the past they have been
lumped into the "Trilobitoidea"; some species such as Anomalocaris are now placed within the
Protarthropoda (separate and considered to be more primitive than the “true” Arthropoda)
- the Middle Cambrian Burgess Shale fauna of British Columbia has fossils with preserved softpart anatomy; most forms have the first pair of appendages modified into antennae with the other
appendages undifferentiated
2. Class Trilobita
a. Soft Parts
a1. Appendages - biramous (differentiated into a gill and leg) OR uniramous, (forming
antennae)
a2. Body systems
- Sensory apparatus - appendages modified as antennae; lateral paired eyes either compound
(holochroal) with closely packed hexagonal lenses OR aggregate (schizochroal) eye; some
species with eye reduced or lost; also with ventral stiff tactile bristles
- Muscular and digestive systems complex
- Respiration by external gills
- Reproduction = sexes separate
- 3 larval stages (planktonic); adults usually benthonic but some planktonic or nektonic (spinous
forms); molting probably occurred 20-30 times during life of individuals
b. Hard Parts
b1. Exoskeleton mineralized, chitinous
b2. Body divided transversely into cephalon (head shield or tagma), thorax (series of separate
articulate segments); pygidium (tail shield or tagma)
b3. Body longitudinally trilobed - with 1 axial lobe (probably contained internal organs) and 2
pleural lobes (lateral to axial lobe and probably to protect appendages or for hydrofoils; pleurae =
lateral thoracic segments)
b4. Facial sutures
- line along which exoskeleton of head split when trilobite molted; may be limited to margin of
cephalon or pass as fine line along dorsal surface of cheek
- Opisthoparian suture = crosses cheek, passes along medial border of eye and intersects posterior
margin of cephalon medial to genal angle (Genal angle = posterior lateral corner of cephalon)
- Proparian suture = crosses dorsal surface of cephalon, passes along medial edge of eye,
intersects lateral border of cephalon in front of genal angle
PALEO LECTURE, PAGE 60
- Gonatoparian suture = bisects genal angle
- Marginal suture = suture entirely along lateral edge of cephalon
Other Features Important in Classification Include:
- Cranidium = central part of cephalon including axial lobe and bounded by the facial suture
- Genal spine = spine extending posteriorly from posterior-lateral corner (genal angle) of
cephalon
- Glabella = elevated axial portion of cephalon; represents anterior part of axial lobe
- Hypostoma = plate on under surface of cephalon directly in front of mouth
- Occipital ring = narrow posterior part of glabella set off from rest of glabellum by an occipital
furrow
- Rostral plate = median, ventral plate in cephalon between doublure of cranidium and
hypostoma
c. Classification of the Class Trilobita
- typically in seven to eight orders (some authors have as few at two!), 13 suborders, 30
superfamilies based primarily on 1) cephalic axial characters (glabella, shape, furrows, etc.), 2)
pattern of facial sutures, 3) morphology of pygidium (especially caudalization)
c1. Order Agnostida = smallest trilobites; eyeless (except 1 family) trilobites with subequal
cephalon and pygidium; possess only 2-3 thoracic segments; probably planktonic; 2
suborders; Lower Cambrian - Upper Ordovician
c2. Order Redlichiida = first trilobites; large and spinose; large, semicircular, relatively wide
cephalon; typically large genal spines; numerous thoracic segments; facial sutures
opisthoparian or fused; Glabellar segments typically distinct; pygidium small to
rudimentary; eyes commonly form elongate crescents; 3 suborders; Lower to Middle
Cambrian
c3. Order Corynexochida = subelliptical, typically with large pygidium, cephalon semicircular
(commonly with large genal spines); glabella distinct, expands forward; eyes elongate
and narrow; Opisthoparian sutures; rostral plate fused with hypostoma or rudimentary.
Thorax with 5-11 segments with spinose pleurae; Lower to Upper Cambrian
c4. Order Ptychopariida = typically opisthoparian, more rarely proparian or with marginal
sutures; three or more thoracic segments present; pygidium small (early) to large; eyes
more distinct from eye ridges than in Redlichiida. Glabella typically tapers forward
PALEO LECTURE, PAGE 61
(thought to be closely related to Redlichiida and ancestral to all post-Cambrian
trilobites except agnostids, but may be a polyphyletic group); 5 suborders, 26
superfamilies; Cambrian - Ordovician
c5. Order Phacopida = typically proparian or gonatoparian, rarely opisthoparian. Glabella
either expanding or tapering forward. Pygidium typically medium to large; 3 suborders:
Lower Ordovician to Upper Devonian
c6. Order Lichida = glabella broad, extending to anterior border; glabellar furrows elongated
longitudinally; occipital ring tends to fuse with glabellar lobe. Opisthoparian.
Pygidium large, includes leaflike or spinose pleurae; Lower Ordovician to Upper
Devonian.
c7. Order Odontopleurida = Strongly convex cephalon. Glabella widest at occipital ring; ring
elongate posteriorly and commonly bearing tubercles or spines. Opisthoparian. Large
genal spines typical; small spines on anterior border of cephalon; Pleurae each bear pair
of spines, posterior one long. Paired spines on pygidium; Lower Ordovician to Upper
Devonian
c8. Order Proetida = glabella large and vaulted, well defined, usually with genal spines, narrow
and backwardly tapering rostral plate, opisthoparian, eyes holochroal and usually large,
long hypostome. Thorax with eight to ten segments. Isopygous pygidium, with
pygidium usually furrowed and not spiny; Ordovician - Permian.
d. Paleoecology
- Marine only
- Larvae probably mostly planktonic/nektonic, adults probably mostly benthonic but many in
other environments
Adaptations versus environment:
- Vagile benthonic tendencies include reduction or loss of pygidia
- some Odontopleurida with ventral cephalic spines to prop themselves on sea floor
- Burrowing (fossorial) trilobites with pygidia with large surfaces (many incurved); lose external
sculpture; eyes reduced or lost (or eyes tall); prominent pygidial spines (also serve as mooring
function)
- Nektonic trilobites with pygidia with large surfaces; bodies lightly constructed; large eyes;
expanded glabella (may have contained fat); ovate body shape
- Planktonic trilobites with very spinose forms; expanded glabella; ovate body shape
e. Biostratigraphy - important index fossils in the Cambrian with a number of biozones; also
used in the Ordovician, Silurian and Devonian
D. Superclass Onychophora ("Velvet worms")
- wormlike arthropods that represent "missing links" between the segmented worms (annelids)
and the joint-legged segmented arthropods
- Fossil onychophorans are marine; Modern onychophorans are usually found in dense tropical
PALEO LECTURE, PAGE 62
rain forests beneath rocks and boulders and in humus
- Cambrian - Holocene
XIII. Crustaceans
Phylum Arthropoda, Superclass Crustacea
A. Biology
- Head composed of several fused cephalic segments (somites); 2 somites preoral and bear 2
pairs antennae; 1 pair of antennules present; 3 somites postoral and bear 2 maxilla and 1
mandible; thorax with 2 (ostracodes) to more than 40 (some branchiopods) somites; some two
branched (biramous) appendages present; with nauplius larva (a microscopic, free-swimming
larval stage, typically with three pairs of appendages)
B. Classification
- 9 classes; 2 unknown as fossils
1. Class Cirripedia
- barnacles
- free swimming larval stage settles down on head, lose bivalve shell; attach by antennules;
secrete overlapping calcareous plates; food brought to mouth by biramous and fringed legs; 5
orders; Silurian - Holocene
- marine, mostly shallow water; food plankton and organic detritus, some parasitic
2. Class Branchiopoda
- "fairy shrimp", "brine shrimp", "waterfleas"
- most primitive crustaceans; large number of body segments (some with more than 40 somites);
small, shrimp-like animals; leaflike appendages; carapace univalved or carapace absent; Range:
Proterozoic(?); Cambrian - Recent
- fresh to brackish water; supersaline water (brine shrimp), rarely normal marine; tolerates wide
variety of temperature and drying and freezing of pools
- 3 superorders and 4-7 orders; only 1 order (conchostracans) important as fossils
Order Conchostraca = chitinous + calcium carbonate carapace consists of 2 flaps continuous
across the dorsal region; useful in microbiostratigraphy (mainly because preserved in high stress
environments - glacial lakes, supersaline conditions)
3. Class Copepoda
- the Copepods are the most abundant zooplankton in the World's oceans (there are also include
benthonic and parasitic representatives); they are common in temperate and subpolar waters
- copepods are about 0.3 to 8 millimeters long, with a jointed exoskeleton and 2 bristly antennae
that form a filter-feeding device in front of the mouth
4. Class Malacostraca
- lobsters, crabs, crayfish, shrimp, also sandhoppers and pill bugs (sow bugs)
PALEO LECTURE, PAGE 63
- Most with body composed of approximately 20 segments (6 fused to form head, 8 thorax, 6
abdomen; also 1 telson on end of abdomen); appendages present on all body segments; anterior
antennules uniramous, 1 pair biramous antennae; 1 pair heavy mandibles, 2 lighter pairs
maxillae; 2 superorders; 5-8 orders; Range:Cambrian-Recent
- marine, freshwater, terrestrial; most decapods in littoral zone; estuarine, swamp and lagoonal
environments often favored by fossil forms (Ex. = Pennsylvanian coal swamps); decapods mostly
carnivorous, others filter feeders
a. Subclass Eumalacostraca
- Carapace covers entire thorax and fused to all thoracic segments; abdomen with six segments;
includes the decapods
Order Decapoda - crabs, lobsters, shrimp, prawns, crayfish; Range: Triassic - Recent
Order Phyllocarida - "leaf shrimp"; Cambrian - Recent
5. Class Ostracoda
- usually small (0.5-4 mm long) but may exceed 20 mm in length; body divided into head and
thorax; carapace bivalved, with hinged articulation; inside of shell with central and dorsal muscle
scar fields (muscle scars used in classification)
- omnivores, herbivores, some scavengers and a few commensal or parasitic; freshwater,
brackish, marine, some terrestrial (forest humus); almost all latitudes and depths (but most above
photic zone); most pelagic and benthic from shoreline to several thousand meters
- useful for biostratigraphy (abundant in many environments)
- 6 orders (1 of these uncertain); Lower Cambrian - Recent; the following two are the most
important
Order Palaeocopida (Beyrichicopida) = carapace well calcified; long, straight cardinal margin;
many with lobes and sulci; Ordovician - Triassic, Tertiary(?)-Recent(?); includes most
Paleozoic ostracodes (500 genera)
Order Podocopida= carapace well calcified; adductor muscle scars (close valves) well-developed;
includes all recent freshwater forms and most modern marine) Geologic Range: Ordovician Recent; inclues most Mesozoic and Cenozoic ostracodes (1200 genera)
XIV. Arthropods from Shoals to Air
A. Phylum Arthropoda, Superclass Chelicerata (Cheliceriformes)
- body consists of prosoma (cephalothorax) and opisthosoma (abdomen; usually 12 segments);
Prosoma with 6 pairs of appendages (2-4 jointed pincers = chelicerae, chelae; pedipalps
(orginally for locomotion but modified for grasping, sensing, or chewing); no antennae; aquatic
or terrestrial; scavengers or carnivores; Cambrian - Recent
PALEO LECTURE, PAGE 64
1. Class Merostomata
- body typically divided into two parts (a cephalothorax/prosoma and an abdominal
tagma/opisthosoma); with anterior claws (chelicerae); opisthosomal appendages biramous, with
one branch serving as a gill; with 150-200 thin leaf gills; terminal segment bears a spine (telson);
marine, freshwater; Cambrian - Recent
a. Subclass Xiphosura ("horseshoe crabs")
- typically wide and short body with long telson; opisthosomal segments typically fused; 6 pairs
legs (1 pair chelicerae, 4 pairs walking, last pair "pushers" for forcing animal through mud)
- Classification = 3 orders
Ecology/Paleoecology - all modern xiphosurans marine; migrated from marine to
brackish/freshwater during Devonian; Permo-Carboniferous with many freshwater forms
- Limulus (horseshoe crab) found in shallow water; eat worms and soft molluscs; Triassic-Recent
b. Subclass Eurypterida
- Biology = opisthosoma with 12 free segments excluding telson; 6th pair of appendages
typically oar-like; sexual dimorphism (male with claspers); up to approximately 3 meters long
- Classification = approximately 19 genera
- Paleoecology = found in fresh or brackish water but NOT generally found with "normal
marine" invertebrates; possibly preferred lagoonal with high and low salinities; nektonic;
carnivorous
Biostratigraphy: Ordovician - Permian (most common Silurian - Devonian)
2. Class Arachnida
- includes scorpions, spiders, ticks, mites
a. Biology = body with cephalothorax and abdomen (fused in ticks and mites); cephalothorax
bears 6 pairs appendages (no antennae or mandibles); first two appendages modified for feeding,
last four for locomotion; air-breathing, with respiration by book lungs (leaf-like plates containing
blood vessels) or tracheae (ramified tubules)
b. Classification = 5 orders based primarily on segmentation (number of segments; fused or
unfused) and form of chelicerae (scorpions with pincers, spiders without)
c. Ecology/Paleoecology - terrestrial, solitary, carnivorous or parasitic
d. Biostratigraphy: Silurian - Recent
Scorpions = Upper Silurian-Recent
Spiders = Middle Devonian-Recent (approximately 250 fossil species)
Ticks and mites = Devonian-Recent; very sparse fossil record
B. Phylum Arthropoda, Superclass Myriapoda
PALEO LECTURE, PAGE 65
1. Biology
- wormlike, with multiple segments bearing legs; single pair antennae; mandible "toothed" for
chewing; skeleton chitinous (may be strengthened by carbonates); air breathing through tracheae
2. Classification - 6 classes; relatively rare as fossils
a. Class Chilopoda
- centipedes
-all body segments with single pair of legs except first (with a poison claw) and last];
Cretaceous-Holocene
b. Class Diplopoda
- millipedes
- some body segments with 2 pairs legs
- originally freshwater, one of first invertebrate groups to venture onto land; PennsylvanianHolocene
3. Ecology/Paleoecology
- terrestrial; Chilopoda carnivorous; Diplopoda primarily eat decaying vegetation; fossil
representatives probably similar in habits
C. Phylum Arthropoda, Superclass Hexapoda, Class Insecta
- Hexapoda includes four classes; only Class Insecta with extensive fossil record
1. Biology
- Body with three distinct tagma (head, thorax, abdomen); head with 1 pair antennae; compound
eyes; 3 pairs mouth parts (1 pair mandibles, 2 pairs maxillae); 3 thoracic segments with pair of
jointed legs on each; wings often present; abdomen usually with 11 segments or fewer (6-8);
respiration by tracheae; sexes generally separate; many with metamorphosis
2. Classification - approximately 25 to 30 orders; over 1 million modern species and
approximately 13,000 fossil species
a. Apterygota
- small, wingless insects (include the bristletails and their kin); Devonian - Recent
b. Palaeoptera
- primitive winged insects that lack the ability to fold their wings
- the Palaeoptera may be a paraphyletic group
b1. Protodonata - "ancestral dragonflies" (often differentiated into the Palaeodictyptera and
Megasecoptera); wingspreads up to 0.7 to 0.75 meters and bodies 0.3 to 0.4 meters long;
Pennsylvanian - Permian
PALEO LECTURE, PAGE 66
b2. Odonata (dragonflies) = Early Permian - Recent
c. Neoptera
- winged insects that can flex their wings over their abdomens
c1. Orthoptera (grasshoppers, crickets) = Pennsylvanian - Recent
c2. Hemiptera (bugs, aphids) = Early Permian - Recent
c3. Coleoptera (beetles) = Late Permian - Recent
c4. Diptera (flies, mosquitoes) = Triassic - Recent
c5. Hymenoptera (bees, wasps, ants) = Triassic - Recent
c6. Lepidoptera (butterflies) = Cretaceous - Recent
c7. Blattodea (cockroaches) = Pennsylvanian - Recent
3. Ecology/Paleoecology
- essentially all environments; primarily terrestrial but many with aquatic larvae
4. Biostratigraphy
- sometimes useful in microbiostratigraphy; Geologic Range: Middle Devonian - Recent
- Note: The millipedes, centipedes and insects are often placed within a "phylum" or
"subphylum" Uniramia, based upon the shared presence of uniramous appendages in these
groups
XV. Snails and Their Kin
A. Phylum Hyolitha
- sometimes grouped with the molluscs
1. Biology
- operculate, shell elongate and tapering; apical portion commonly with septa; most species with
elongate paired structures (props)
- Order Hyolithida with a ligula (anterior shelf-like extension of the aperture) and a helens (thin,
scimitar-shaped lateral appendages between the operculum and conch; for stabilization?)
2. Paleoecology
- originally believed to be planktonic/nektonic but now believed to be vagile benthonic (used
props to "pole" animal across substrate?) or sessile benthonic; may have been deposit-feeders
PALEO LECTURE, PAGE 67
3. Biostratigraphy
- most abundant during Cambrian, then declined rapidly; extinct in Late Permian
B. Criconarids
- cone-like, probably planktonic organisms sometimes placed with the molluscs; OrdovicianDevonian
- the major group of criconarids are the Tentaculitids, typically represented by 1-80 mm long
straight cones ornamented with transverse rings or striae
C. Phylum Mollusca
- Comprise approximately 11% of all extant and fossil species of invertebrates and vertebrates
1. Mollusc Biology
a. Soft Parts
a1. Unsegmented (except Monoplacopherans) but probably share common ancestry with
"segmented" arthropods and annelids
a2. bilateral symmetry (except gastropods)
a3. Body regions
Head = with tentacles and eyes (lost in bivalves)
Foot = ventral and muscular
Visceral Mass (visceral hump) = coiled in gastropods; internal organs concentrated in this mass
Mantle (Pallium) = dorsal soft skin or sheet of tissue overgrowing visceral mass; secretes
calcareous shell with an organic matrix
Mantle cavity = space at posterior end of visceral mass containing paired gills (Ctenidia) used for
breathing and (in bivalves) for filter-feeding; anus, excretory and reproductive systems open into
the mantle cavity
a4. Digestive Tract
- with mouth, commonly with jaws; buccal cavity with radula (horny ribbon for rasping)
a5. Organs and organ system
- usually 3-chambered heart, usually 1 pair of gills or with lung, sexes usually separate;
hermaphroditism (both sexes in same animal) widespread; usually trochophore larva (free,
swimming ciliated larva), followed by veliger larva (top-shaped with equatorial flange (velum)
bearing cilia); or NO larval stages
PALEO LECTURE, PAGE 68
b. Hard parts
- most with external calcareous shell (aragonite and calcite)
b1. Shell structure
- shells with 5 basic structures; most common are prismatic and crossed laminar; best seen under
petrographic microscope
Prismatic structure = single or compound crystals with long dimensions at right angles to the
plane of the shell; often dull or chalky luster
Crossed laminar structure = laminae inclined in opposite directions to increase strength of shells
(usually made of aragonite)
Foliated structure= mica-like
Nacreous structure = thick aragonite layers separated by organic substance
Homogeneous structure = no structure under plane light
2. Classification
Class Aplacophora = no shell, worm-like; no fossil record
Class Monoplacophora
Class Polyplacophora
Class Scaphopoda
Class Gastropoda
Class Rostroconchia
Class Bivalvia (Pelecypoda)
Class Cephalopoda
D. Phylum Mollusca - Class Monoplacophora
1. Anatomy
a. Soft Parts
- 1 living species with segmentation (paired gills, muscles and other structures)
b. Hard parts
- cap, spoon-shaped or arched single shell; shell aragonite or aragonite + calcite
2. Classification - 4 orders; bellerophontids are the most important fossils (Cambrian - Early
Triassic)
3. Paleoecology - most Early to Mid Paleozoic in epicontinental seas; during Late Paleozoic? or
Early Mesozoic moved to deeper water; most were probably deposit feeders
PALEO LECTURE, PAGE 69
4. Biostratigraphy - Lower Cambrian-Triassic (fossils); 1 modern genus
E. Phylum Mollusca - Class Polyplacophora (Amphineura)
- chitons and their relatives
1. Biology
a. Soft Parts
- with encircling girdle; flat foot and ventral sole adapted for creeping; 3-80 pairs of gills; low
visceral hump; rudimentary head; radula usually present
b. Hard Parts
- aragonite shell composed of eight overlapping, articulate plates (valves) in series along middorsal line or No shell
- fossils of chitons typically consist of loose, disarticulated valves
2. Classification - 2 orders differentiated by valve structure
3. Ecology/Paleoecology
- marine, vagile benthonic (sluggish bottom crawlers); live on or under rocks, typically within the
intertidal zone; herbivores, omnivores
4. Biostratigraphy
- Late Cambrian to Recent; most abundant in Cenozoic
F. Phylum Mollusca - Class Scaphopoda
- "tusk shells"
1. Anatomy
a. Soft parts
- elongate body; head and appendages project from wider anterior opening (aperture); other end
of shell (apex) extends above sea floor surface and produces exhalent/inhalent currents; head
with many prehensile processes (captacula) protruding from large gills which collect food
b. Hard parts
- 3-layered tusk-like aragonite shell; apex may be simple, slitted or notched; tube upright
2. Classification
- two families based primarily on ornamentation
3. Ecology/Paleoecology
- marine, semi-infaunal benthonic deposit-feeding burrowers; usually sublittoral or bathyal
PALEO LECTURE, PAGE 70
4. Biostratigraphy
- Range: Middle Ordovician to Recent; mostly Mesozoic-Cenozoic
G. Phylum Mollusca - Class Gastropoda
1. Biology
a. Soft Parts
- distinct head, fused with sole-like foot (for creeping); radula normally present; torsion present
(reorient organs; twists so that the mantle cavity lies alongside the head; balances animal over the
foot)
b. Hard Parts
- where present shell (conch) is single (univalve), calcareous (mostly aragonite; mostly lamellar
and nacreous structure)
b1. Types of Coiling
Planispiral - coiling in a single plane
Pseudoplanispiral - shell coiled in a single plane, but cannot be divided into symmetrical halves
by this plane
Conispiral - coiling deviates greatly from a single plane; spirally wound
- most conispiral shells are coiled clockwise down the cone (dextral), but a few are coiled in a
counterclockwise direction (sinistral)
b2. Morphology of conchs
Apex = tip of shell; point of beginning of shell growth
Whorl = single complete loop of a spiral shell
Suture = junction between two whorls
Spire = coiled gastropod shell exclusive of body whorl
Body whorl = last formed single complete loop of a spiral shell
Operculum = plate-like structure attached to the snail's foot; protects the animal by sealing the
aperture (opening)
2. Classification - 3 subclasses based on torsion and gill position
a. Subclass Prosobranchia - almost all commonly observed snails; shell cap-shaped or
PALEO LECTURE, PAGE 71
conispiral; with torsion; primarily marine, some freshwater and terrestrial; Geologic
Range: Lower Cambrian-Recent
a1. Order Archaeogastropoda - fully torted; right gill usually lost; shells usually low-spired and
equidimensional; inner layers of shells usually nacreous; 8 suborders; includes
essentially all Pennsylvanian gastropods; Range: Lower Cambrian-Recent
a2. Order Mesogastropoda - with single left gill; usually conispiral and often with inhalent
notch; shell often porcelaneous; Range: Middle Ordovician to Holocene; include many
common Mesozoic and Cenozoic types
a3. Order Neogastropoda - single left gill; shells conispiral with siphonal notch or canal;
carnivores; Range: Cretaceous to Recent (these are the dominant Cenozoic and modern
snails)
b. Subclass Opisthobranchia - with detorsion and one gill; shell tends to be reduced or absent
(therefore poor fossil record except for the pteropods = marine nektonic; often thin shell;
often operculate; Geologic Range: U.Cretaceous - Recent)
c. Subclass Pulmonata - most shell-bearing but lack operculum; with detorsion; Mantle cavity
acts as a lung; Most terrestrial and freshwater; Geologic Range: Pennsylvanian - Recent
3. Ecology/Paleoecology
- most shallow marine, herbivorous, vagile benthonic
Prosobranchia = most marine, some freshwater, few terrestrial
Opisthobranchia = only important fossil is pteropods (exclusively marine)
Pulmonata = terrestrial or fresh water
4. Biostratigraphy
- Range: Lower Cambrian to Recent
- Useful on a species level and for local biostratigraphy in Carboniferous, Permian, Cretaceous
but no specific bizones
XVI. Bivalves: Clams, Mussels, and Oysters
Phylum Mollusca - Class Bivalvia (Pelecypoda)
A. Biology
1. Soft Parts
- Body bilaterally symmetrical; compressed
PALEO LECTURE, PAGE 72
- Mantle grows down and completely envelops "head", foot and visceral mass
- Head reduced to rudimentary condition
- Foot usually wedge-shaped (movement by plowing)
- Two gills with abundant cilia
- Inhalent and exhalent siphons present (for inflow and outflow of water and body wastes)
- Complex nervous system; closed circulatory system and digestive system
2. Hard Parts
- Shell bivalved, of calcium carbonate (calcite, aragonite or both); shell with 2-3 layers
Shell Morphology:
- Dorsal = direction toward part of shell containing hinge line
- Beak = sharp-pointed projection; inital point of shell growth
- Anterior = part of shell containing mouth (beaks of most pelecypods point anteriorly)
- Growth line = concentric lines parallel to shell margin
- Ventral = lies opposite hinge line
- Umbo = strongly convex portion of valve adjacent to beak
- Hinge line = edge of valve along dorsal margin that is in permanent contact with opposite valve
- Lunule = depressed plane or curved area along hinge line in front of beak, equivalent to anterior
part of cardinal area
- Escutcheon = depressed plane or curved area along hinge line behind beak, equivalent to
posterior part of cardinal area
- Plane of commissure = surface approximately coinciding with valve margins
- Hinge plane = edge of valve along dorsal margin which is in permanent contact with opposite
valve
- Hinge teeth = projections from hinge plate for articulation of valves
- Lateral teeth = projections from hinge plate nearly parallel to hinge line, situated in front or
behind cardinal teeth
- Cardinal teeth = projections vertical or oblique to hinge line directly beneath or closely adjacent
to beak; they fit into sockets of opposite valve
PALEO LECTURE, PAGE 73
- Socket = depression in hinge plate for reception of a hinge tooth of opposite valve
- Auricle (ear) = forward or backward projection of shell along hinge line in some pelecypods
- Plica = ribs involving entire thickness of shell
- Costa = ridge formed by thickening of shell surface
- Ligament area = portion of surface along hinge line to which ligament is attached
- Posterior = shell direction toward anus and siphonal opening (usually opposite beak inclination)
- Adductor scar = impression on inside of valve made by attachment of muscle which functions
for closure of valve
- Pallial sinus = inward deflection of posterior part of pallial line, defining space for retraction of
siphons
- Pallial line = ventral linear depression on inside of shell
- Ligament groove = linear depression in cardinal area or ligament area masking attachment of
ligament fibers
- Cardinal area = plane or curved surface between beak and hinge line
- Valve = part of shell lying on either side of hinge line
B. Classification of Bivalves
1. Most important features for classifying fossil bivalve shells are:
a. Dentition
- important at all taxonomic levels; most important types of dentition are Edentulous (simplest
hinge type; with ligament but lacks teeth), Taxodont (many small short teeth of variable shape,
which most often occupy most of the length of the dorsal margin), Actinodont (dentition
composed of pseudocardinal and pseudolateral teeth), Cyrtodont (lacks cardinal teeth),
Parallelodont (posterior lateral teeth parallel to dorsal margin), Isodont (two subequal prominent
hinge teeth on one valve and corresponding sockets in the other), Heterodont (teeth are separated
by an edentulous space; teeth are of distinct type with cardinals beneath beak and laterals in front
or behind or both)
b. Form of ligament insertion on the valves (especially important at the family or superfamily
level)
PALEO LECTURE, PAGE 74
c. State of adductor muscle scars (usually at the order to superfamily level)
d. State of pallial line (mainly at the family level and below)
e. Shell shape (all levels from superfamily downwards)
f. Shell mineralogy and microstructure (mainly at the superfamily level)
2. Bivalve Taxonomy
- superfamily level of bivalve classification is most stable and is often used to divide the bivalves
into major groups; with more than 50 superfamilies (but we will only cover the following
subclasses)
a. Subclass Palaeotaxodonta
- Early Cambrian to Holocene
- stratigraphically oldest and anatomically the most primitive pelecypods
- all marine and infaunal; most detritus feeders; palaeotaxodont nuculoids burrow into sediment
and gather food particles with the fleshy extensions of their labial palps
- no adult byssus (thread-like attachment structures); usually with equivalved shell and taxodont
teeth (with numerous, approximately equal, undifferentiated hinge teeth)
b. Subclass Isofilibranchia
- Early Cambrian to Holocene
- most shallow marine or brackish, some freshwater; mainly epibenthic, sedentary and attach by a
well-developed byssus
- with simple tooth structure or edentulous (lack hinge teeth); typically heteromyarian (posterior
adductor scar large) and integripalliate (pallial line forms a simple arc); anterior portion of valve
typically greatly reduced
c. Subclass Pteriomorpha
- Early Ordovician - Holocene
- most shallow marine, some estuarine, few freshwater; all suspension feeders ; byssate or
cemented to substrate as adults
- most with reduced anterior end and develop lobes, auricles and/or wings; many are
inequivalved; typically isomyarian (adductor scars are equal size) and lack well-developed
inhalent and exhalent siphons; dentition variable
- include arc shells, oysters, pen shells, file shells and scallops
d. Subclass Heteroconchia (Heterodonta)
- Early Ordovician to Holocene
- most shallow marine but also include most living freshwater species; most are burrowers
(infaunal) and suspension (siphon) feeders
- most with heterodont dentition [hinge teeth differentiated into vertical cardinals situated below
the beak (umbo) and with subhorizontal lateral teeth on either side] and are usually isomyarian
- include freshwater mussels, cockles, piddocks, giant clams, coquina clams, surf clams and
PALEO LECTURE, PAGE 75
rudists (Superfamily Hippuritacea; Jurassic-Cretaceous; important Cretaceous reef-formers)
e. Subclass Anomalodesmata
- Middle Ordovician - Holocene
- marine; most suspension-feeders; shells usually edentulous (lack hinge teeth) and isomyarian,
siphons commonly present, exterior shell ornamentation often with granules or conical spines
C. Class Rostroconchia
- earliest Cambrian through latest Permian; probable ancestors of the Bivalvia and Scaphopoda
- usually with small shells (less than 2 centimeters) but some Devonian types with shells up to 15
centimeters
- consist of bivalve shells that were joined permanently across the top (formed a "taco shell"-like
structure); shell apparently broke periodically along the margin to allow growth
- posterior portion of shell typically developed into an elongate tube
XVII. Feet Before Heads: the Nautiloids and Their Relatives
A. Phylum Mollusca - Class Cephalopoda
- Probably the most studied group of fossil invertebrates; have been used extensively as index
fossils
1. Biology
a. Soft Parts
- Body = bilaterally symmetrical; most planispiral
- Head = well developed; anterior in position; mouth with crown of mobile and prehensile
tentacles and contains radula and upper and lower jaws; eyes well-developed; hood located above
head (tough, fleshy operculum for closure of aperture when head is retracted into the shell)
- Foot = highly modified; with hyponome (muscular funnel or siphon for powerful exhalent water
current ejection for jet propulsion)
- Gills = single pair in dibranchiates (ex. Octopus); two pairs in tetrabranchiates (ex. Nautilus)
- Body Systems = heart 2-3 chambered; Respiratory system complex; Nervous system highly
organized
- Reproduction = sexes separate; development direct (from embryo to adult without trochophore
or veliger larval state); internal fertilization
b. Hard Parts
- Shell calcium carbonate aragonite/nacreous OR shell reduced/absent
PALEO LECTURE, PAGE 76
b1. Shell morphology:
- Whorls = shell coils
- Living chamber = large open receptacle for soft parts
- Camera = gas chamber in shell
- Phragmocone (phrag) = chambered portion of conch behind living chamber
- Adapertural (adoral) = portion of conch nearest aperture
- Adapical = portion of conch nearest apex
- Venter = part of whorl farthest from axis of coiling
- Dorsum = portion of conch which is uppermost
- Septum = curved calcareous partition dividing shell into chambers
- Suture = line of junction of septum with walls of shell
- Saddle = forward (adapertural) flexure of suture
- Lobe = flexure of suture toward rear (adapically)
- Protoconch = initial chamber of shell
- Siphuncle = tube extending from back of living chamber through septa to protoconch
- Connecting ring = calcareous ring forming wall of siphuncle between septa
- Umbilicus = depression (or in some an opening) in axis of coiling formed by diminishing width
of whorls towards axis
- Annulus = line along which animal is attached to wall of living chamber
- Septal neck = flexure of septum along siphuncle forming a short tube or funnel
- Siphuncular (siphonal) deposit = calcareous deposits along siphuncle; in some nautiloids of
considerable thickness
- Cameral deposit = calcareous deposits on septa and/or walls of camera
PALEO LECTURE, PAGE 77
b2. Types of Shells:
- Cyrtocone = curved, slender shell
- Orthocone = straight, slender shell
- Lituiticone = coiled in early stage, straight at maturity (named after Lituites)
- Brevicone = short, blunt shell
- Longicone = long shell
- Ascocone = with slender curved early stage and short, blunt mature stage in which gas
chambers overlie living chamber (named after Ascoceras)
- Gyrocone = loosely coiled shell (like Gyroceras)
- Advolute shell = coiled, whorls touching
- Involute = type of coiled shell in which part of outer whorl extends in toward center of coil and
covered part of adjacent inner whorl
- Convolute shell (nautilicone) = outer whorls embracing inner ones (like Nautilus)
- Conispiral (trochoid) = coiled like a screw
- Planispiral = type of coiled shell in which whorls lie in a single plane
- Heteromorph = ammonoid shell type in which shell is NOT planispiral and/or in which walls of
coil are not in contact
b3. Types of Sutures:
- Goniatite suture = type of suture characterized by simple fluting consisting of single series of
lobes and saddles (i.e., with first order lobes and saddles); flexures undivided (Devonian Permian; 1 Triassic genus, 1 Cretaceous genus)
- Ceratite suture = type of suture characterized by presence of small lobes and saddles on major
lobes (second order lobes and saddles) (Mississippian - Triassic; a few Cretaceous; are the
predominant Triassic ammonoids)
- Ammonite suture = type of suture characterized by complex fluting; smaller secondary and
tertiary lobes and saddles developed on larger primary set [Permian - Cretaceous (especially
Jurassic-Cretaceous)]
PALEO LECTURE, PAGE 78
2. Classification of Cephalopods
a. Subclass Nautiloidea
- small to large conchs, shells orthoconic (straight), Cyrtoconic (curved, slender), coiled-involute
(part of adjacent inner whorls covered); siphuncle position and diameter variable with long or
short segments; septal flexure of septum at siphuncle forming short tube or funnel necks usually
straight, cylindrical and extending only short distance to preceding septum (but sometimes
curved concave-outward); Geologic Range: Upper Cambrian - Recent; 8 orders, 700 genera
Order Nautilida = coiled shells; Ordovician - Recent
b. Subclass Endoceratoidea
- Medium to very large conchs [up to 10 meters long!]; usually orthoconic (generally longiconic);
rarely cyrticonic (curved, slender) or breviconic; siphuncles medium-large, usually located
ventrally; siphuncular deposits consist typically of conical sheaths (endocones); Geologic Range:
Upper Cambrian?; Lower Ordovician - Silurian; 2 orders
c. Subclass Actinoceratoidea
- Medium to very large conchs up to 6 meters long, usually orthoconic; cameral and siphuncular
deposits present; Geologic Range: Late Cambrian?, Middle Ordovician to Late Mississippian; 1
order
d. Subclass Bactritoidea
- Orthoconic to weakly cryptoconic (shells hidden inside tissue); longiconic or breviconic; septa
concave anteriorly; NO siphuncular or cameral deposits; siphuncle narrow and in contact with
ventral wall; sutures simple with at least one small, shallow V-shaped ventral lobe; probably
ancestral to all recent cephalopods (cuttlefish, squid, octopus) except Nautilus and possibly
ancestral to ammonoids; Geologic Range: Devonian - Upper Triassic; 1 order
e. Subclass Ammonoidea - see discussion below
f. Subclass Coleoidea - see discussion below
3. Ecology/Paleoecology of Primitive Cephalopods
a. Subclass Nautiloidea
a1. Locomotion:
- gas (argon/nitrogen) provides buoyancy; addition of camerae and cameral and siphuncular
deposits add ballast; camerae and septa brace against water pressure
- coiling resulted for solving problems of hydrostatic inequilibrium
- ancestral brevicones and cyrtocones may have been vagile benthonic (as indicated by preserved
"color" patterns; excessive "ballast")
- some groups nektonic (egg-shaped with Y- or T-shaped aperture)
- coiled-shelled forms either crawlers or swimmers
PALEO LECTURE, PAGE 79
a2. Distribution:
- most fossil orthocones probably in clear, shallow water
- faunas rich in nautiloids with sparse ammonoids and vice versa
- Feeding - probably most were carnivores
b. Subclass Endoceratoidea
- presence of siphuncular deposits (endocones = conical sheaths) enabled horizontal locomotion;
most benthonic?
c. Subclass Actinoceratoidea
- Cameral and siphuncular deposits present, probably many benthonic
d. Subclass Bactritoidea
- No siphuncular or cameral deposits; probably nektonic
XVIII. "Ammon's Stones" and Naked Cephalopods
A. Phylum Mollusca, Class Cephalopoda, Subclass Ammonoidea
1. Ammonoid Biology
- shell usually coiled (tight planispiral with bulbous, calcareous protoconch); siphuncle small and
marginal; NO siphuncular or cameral deposits; sutures with several lobes and (typically with
secondary lobes and saddles); Geologic Range: Lower Devonian - Upper Cretaceous; 8 orders;
1800 genera (less than 10% Paleozoic, over 90% Mesozoic)
- most Paleozoic ammonoids were "goniatites" belonging to the Order Goniatitida
- Permian through Cretaceous forms had ammonitic sutures (both saddles and lobes are
crenulate); most Mesozoic forms were planispirally coiled but "heteromorph" types with wide
variety of shapes; Cretaceous forms with shell diameters up to 3 meters
2. Biostratigraphy
- Ammonoids nearly became extinct three times (end of Devonian, Permian, and Triassic) before
their total extinction at the end of the Cretaceous; after each near-extinction event underwent a
major adaptive radiation
- Early Devonian ammonoids with primarily agoniatitic sutures (with a few simple undivided
lobes and saddles, with narrow midventral lobes and broad lateral lobes); tendency toward
development of tighter coiling
- Upper Devonian with 30 families, with short ranges and useful biostratigraphically
- goniatitic sutures dominated Mississippian (25 families) and Pennsylvanian (30 families)
- during Permian 27 families present; decrease in goniatitic sutures, with extinction of goniatitic
lineages at end of Permian
- three families survive into the Triassic, with great diversication of the ceratites (80 Triassic
families, almost all ceratites)
- Jurassic and Cretaceous with ammonitic sutures dominating; with 46 Jurassic and 85
PALEO LECTURE, PAGE 80
Cretaceous families
b2. Subclass Coleoidea (Dibranchiata)
- all living cephalopods except Nautilus
- with two arborescent gills in the mantle cavity, 8 to 10 sucker or hook-bearing arms (two of
them, when 10 are present, being developed into long tentacles), and internal shells; some lack
external shell, others with unchambered external shell
Order Teuthida (Teuthoidea) - includes the true squids (Jurassic - Recent); with ten arms;
chitinous shell (the pen) lies above the visceral mass; fossils typically consist of pens, with a few
rare impressions of soft parts
Order Sepioidea (Sepiidae) - include the cuttelfish; flattened dorso-ventrally; 10 arms present;
usually bottom predators; Spirula drifts through deep waters, has an internal chambered shell
Order Octopoda - octopuses; with eight arms and a bulbous body; earliest fossils are impressions
of soft parts from the Upper Cretaceous
Order Belemnoidea (Belemnitida) - include "belemnites" (Upper Mississippian to Upper
Cretaceous); with internal shell consisting of a chambered cone (phragmacone), pro-ostracum
and a guard (sheath, rostrum); well-preserved fossils show the presence of arm hooks and ink
sacs in belemnoids
XIX. Mostly Stemmed Echinoderms
Phylum Echinodermata - includes holothurians (sea cucumbers); echinoids (sea urchins);
asteroids (starfish or sea stars); crinoids (sea lilies) and also extinct types (examples = blastoids,
cystoids)
A. Echinoderm Biology
1. Most with pentameral (5-rayed) symmetry; bilateral symmetry in some fossil groups and in
echinoderm larvae
2. definite head or brain lacking
3. water vascular system present = network of tubes which open freely into surrounding sea
water through hydropores or a madreporite (sieve plate); original function respiratory but tube
feet (podia) used for respiration, locomotion, sensing, food gathering and digging (build burrows)
4. Endoskeleton consists of separate plates, spicules (holothurians) or pieces of calcium
carbonate
5. Organ systems - No heart, no definite vessels; nervous system primitive; respiratory system
PALEO LECTURE, PAGE 81
absent; sexes separate
B. Classification
- The classification of echinoderms is based primarily on the skeletal morphology of the adult
stages. As in most classifications, there is some controversy as to the precise relationships of a
number of groups. However, the following classification is typical. Number of genera is given
(in parentheses), along with the range of each taxon.
Phylum Echinodermata
Subphylum Crinozoa*
Class Crinoidea (1005); Middle Cambrian, Early Ordovician-Holocene
Class Paracrinoidea (13-15); Early Ordovician-Early Silurian
Subphylum Blastozoa
Class Blastoidea (95); Middle Ordovician(?), Middle Silurian-Late Permian
Class Rhombifera (60); Early Ordovician - Late Devonian
Class Diploporiata (42); Early Ordovician - Early Devonian
Class Eocrinoidea (30-32); Early Cambrian - Late Silurian
Class Parablastoidea (3); Early to Middle Ordovician
Subphylum Asterozoa (Eleutherozoa)
Class Asteroidea (430); Early Ordovician - Holocene
Class Ophiuroidea (325); Early Ordovician - Holocene
Subphylum Homalozoa
Class Stylophora (32); Middle Cambrian - Middle Devonian
Class Homoiostela (12-13); Middle Cambrian - Early Devonian
Class Homostelea (3); Middle Cambrian
Class Ctenocystoidea (2); Middle Cambrian
Subphylum Echinozoa
Class Echinoidea (765); Late Ordovician - Holocene
Class Holothuroidea (200); Middle Cambrian(?), Middle Ordovician - Holocene
Class Edrioasteroidea (35); Early Cambrian - Middle Pennsylvanian
Class Ophiocistiodea (6); Early Ordovician - Early Mississippian
Class Helicoplacoidea (3); Early Cambrian
Class Cyclocystoidea** (8); Middle Ordovician - Middle Devonian
Class Edrioblastoidea (1); Middle Ordovician
*Crinozoa and Blastozoa are sometimes placed within the Subphylum Pelmatozoa - both have
radial symmetry, a cup-shaped body (theca) enclosing the viscera, with food-gathering
appendages, and typically with a jointed stem attached to the substrate
**Cyclocystoidea is sometimes placed within the Edrioasteroidea
PALEO LECTURE, PAGE 82
C. Subphylum Crinozoa
- with globular, tightly sutured calyces; most with long erect arms, many arms pinnulate. Most
with theca of several circlets of plates showing well-developed pentameral symmetry. Mouth
nearly central on upper surface, anus lateral; typically attached to substrate by long columnalbearing stems or by cirri. Middle Cambrian to Holocene; approximately 1025 living and fossil
genera in two classes.
1. Morphology of the Crinozoa and Blastozoa
Aboral = direction opposite position of mouth
Ambulacrum = narrow tract or groove extending radially from mouth (Typically tissue overlying
groove thickly ciliated and underlain by radial canal of water vascular system; may subdivide
and extend on to appendages)
Ambulacral plate = calcareous plates forming on floor of ambulacral tract
Ambulacral pore = pore in or between ambulacral plates (for passage of podium or for
connection of podium to ampulla (muscular sacs which connect to cylinders which connect to
podia)
Arms = appendage on oral surface which bears extension of ambulacrus (crinoid)
Calyx (plural, Calyces) = part of crinoid which contains the soft parts; hard part of crinoid
exclusive of the free arms and pelma
Cirrus (plural, Cirri) = jointed appendage of crinoid stems attached to nodals or to centrodorsals;
also rootlike branch at base of some crinoid columns
Columnals = circular, elliptical or polygonal, discoid plates that form the stem
Crown = crinoid calyx and arms
Dorsal cup = portion of calyx below the arm
Interambulacral = area between rays of ambulacra
Madreporite = multiple openings of water vascular system to the exterior
Oral = toward mouth or on same surface as mouth
Pelma = crinoid column with all its appendages and anchorage structures
Periproct = area surrounding anus
PALEO LECTURE, PAGE 83
Peristome = area surrounding mouth
Pinnule = slender, unbranched jointed branchets of an arm (crinoid)
Stem (column) = series of disk-like plates mounted one on top of the other and attached to aboral
end of theca; typically terminal end is fastened to the substrate
Tegmen = ventral surface of calyx (covered by non-calcareous integument or by ambulacrals and
irregularly arranged interambulacrals)
Theca = skeleton of calcareous plates
Thecal plate = calcareous plate forming an element in the theca (usually distinguished from
ambulacral or arm plates)
2. Classification of the Crinozoa
a. Class Crinoidea
- "sea lilies"; approximately 800 living species (but more than 6 times that number of fossil
species); pentamerous (normally and primitively with 5 brachial processes (multiple arms well
developed, plated, movable; pinnulate, uniserial or biserial arms); commonly with long stalk and
sessile (secondarily stalkless and free-living); cuplike calyx of calcareous plates radially arranged
in 3 or more circlets; upper surface with mouth and anus; thecal plates without pores; 4
subclasses, 13 orders; Middle Cambrian, Early Ordovician - Recent
- strictly marine (salinity 24-36 o/oo); cosmopolitan (tropics to arctic); gregarious; feed on
phytoplankton and zooplankton; attachment by root system or cement (but many Jurassic-Recent
crinoids nektonic); most prefer shallow water; arm number varies with temperature (tropical
many; cold/deep waters with few species)
b. Class Paracrinoidea
- may be an artificial group of forms intermediate between "cystoids" and crinoids; calcareous
thecal plates with irregular pattern and variable in number; thecal plates with pores; brachioles
uniserial; 2 orders; Geologic Range: Early Ordovician - Early Silurian (2 orders based on
whether arms attached or arms free of theca)
D. Subphylum Blastozoa
- with globular, tightly sutured thecae, bearing erect brachioles; most with hydropore, gonopore
and accessory thecal respiratory structures. Most attached to substrate by stem composed of
columnals or holdfast composed of many plates in early forms. Early Cambrian to Permian;
approximately 233 genera in five classes
1. Morphology of the Blastozoa
- for other features see Crinozoa
PALEO LECTURE, PAGE 84
Biserial = arrangement of brachiole plates in interlocking double rows; found in many
blastozoans
Brachiole = free appendage of a blastozoan, which bears a food groove (along which food was
transported to the mouth)
Diplopore = paired arrangement of thecal pores in some blastozoans
Gonopore = one or more small openings in theca of many blastozoans, generally located between
the mouth and anus, presumably for discharge of eggs and sperm
Hydropore = generally a slitlike opening adjacent to gonopore, observed in many blastozoans;
interpreted as inlet for a water-circulatory system
Hydrospire = infolded thin-walled respiratory structure of blastoids beneath border of an
ambulacrum or intersecting radial and deltoid plates parallel to an ambulacrum
Lancet Plate = elongate spear-shaped plate occupying central area of an ambulacrum; its outer
surface is marked by a median longitudinal groove and many transverse grooves, which are
concealed by covering plates in perfectly preserved blastoids
2. Classification of the Blastozoa
a. Class Blastoidea
- with conical, bud-shaped or globular theca with four circlets of plates in well-developed
pentameral symmetry; Five short to long ambulacra, underlain by lancet plates, each bearing a
long erect brachiole; eight to ten groups of foldlike hydrospires suspended in coelomic cavity.
Stem usually long but with small diameter. Middle Ordovician(?), Middle Silurian - Late
Permian; about 95 genera.
- filter-fed on phytoplankton and organic detritus; sessile benthonic (fixed to substrate by flexible
stalk; moderate water energy levels); planktonic (some nektonic) larval stage; usually found in
fine grained (shales and micrites) facies; salinity probably normal marine
b. Class Rhombifera (Rhombifera and Diploporita are often termed "cystoids")
- medium-sized brachiole-bearing echinoderms with respiratory rhombs developed in adjoining
plates; rhombs are rhombic in shape and consist of rows of slitlike or porelike openings; with
globular, elongate, lens-shaped or flattened theca with numerous plates usually arranged in four
to five well-defined circlets. Stem of columnals used for attachment or possibly for swimming.
Early Ordovician - Late Devonian
c. Class Diploporita
- medium-sized blastozoan echinoderms with paired pores (diplopores) that penetrate some or
most of the thecal plates; small, erect, brachiole-like appendages; stemmed or stemless; Early
Ordovician - Early Devonian
- "cystoids" were gregarious; rare in general as fossils but locally may be very abundant; filter
PALEO LECTURE, PAGE 85
feeders (brachioles with food grooves); most sessile benthonic (cementation or by means of
prehensile column), few planktonic? (globose forms lacking stem)
d. Class Eocrinoidea
- radially symmetrical thecal plates arranged in circular rows; theca bearing long biserial
brachioles; stem present or absent; sutural pores present in early forms; later forms with very thin
thecal plates; ten families (based on plates, pores, brachioles); Geologic Range: Lower Cambrian
- Late Silurian
- Number of brachioles possibly correlated with temperature/water depth (more brachioles in
warm/shallow water, fewer in cold/deeper)
E. Subphylum Homalozoa
- includes four small classes; with body flattened dorsoventrally; asymmetric or bilaterally
symmetric skeleton; few or no arms; plated "tail" or "stem" (stele or aulacophore); theca of
calcareous plates
1. Classification
- originally placed with the cystoids (as Class Carpoidea); plate ornamentation and arrangement
may suggest that some orders (Cornuta and Mitrata) of Class Stylophora are primitive chordates
ancestral to tunicates, amphioxus, and the vertebrates (but much debated - echinoderm
characteristics of carpoids include calcite plates with an echinoderm-like microstructure and most
bear a food groove); ancestral to other echinoderms? (modification of tentacles would lead to
water vascular system)
- Benthonic? or Nektonic? or Nektobenthonic?; Tail (stele) used for attachment and feeding?
(prehensile?); feeding by cilia, stele, protusible tentacles?
2. Biostratigraphy
Geologic Range: Middle Cambrian - Middle Devonian
XX. Stars, Urchins, and Cucumbers of the Sea
A. Subphylum Asterozoa
- "starfish" (sea stars) and brittle stars; with star-shaped body, open water vascular system;
marine and usually a vagile benthic mode of life
1. Class Asteroidea
- starfish; hollow arms containing large lobes of body cavity and enclosed organs; Early
Ordovician to Recent
- carnivorous (able to extrude stomach through mouth for external digestion); able to withstand
many marine environments
2. Class Ophiuroidea
- brittle stars; slender, whip-like arms; Early Ordovician to Recent
- many detritus feeders, some carnivorous
PALEO LECTURE, PAGE 86
B. Phylum Echinodermata, Subphylum Echinozoa
- globose, without arms or brachioles; radial symmetry (typically 5-fold)
1. Class Helicoplacoidea
- spirally-pleated, expansible, flexible test; 2 spirally arranged ambulacra; Geologic Range:
Lower Cambrian; probably detritus feeders and moved in accordion-fashion
2. Class Edrioasteroidea
- Discoid theca; ambulacral system confined to upper hemisphere of test; 5 ambulacra radiate
from mouth (may curve clockwise or counterclockwise); small irregular plates in interambulacra;
usually attached on lower surface; anus and central mouth on upper; Geologic Range: Lower
Cambrian - Middle Pennsylvanian
- food = plankton; usually found in littoral zones on calcareous, arenaceous and micaceous mud
bottoms
3. Class Ophiocistioidea
- Pentaradiate, free-living forms with dome-shaped body; ventral mouth (peristome) surrounded
by 5 very large armored podia; 2 sizes tube feet [larger for locomotion and feeding (direct food
toward mouth) and smaller for sensory]; carnivorous; Geologic Range: Lower Ordovician Lower Mississippian
4. Class Cyclocystoidea
- sometimes placed within the Edrioasteroidea
- Small, discoidal theca; probably attached to flattened aboral side; numerous plates arranged in
rings; branching ambulacra; Geologic Range: Middle Ordovician - Middle Devonian ; may have
been free-living; food=filter-feeder
5. Class Holothuroidea
- sea cucumbers; sac-like body with small, loosely-attached plates (sclerites) in leathery skin;
mouth at one end surrounded by ring of tentacles formed from podia; anus at other end; Geologic
Range: Middle Cambrian(?), Middle Ordovician - Recent
- found at all depths but between 4000-8500m constitute 50-90% of total biomass; sessile or
vagile; some fossorial (burrowing); normal salinity but tolerates wide variety of temperature and
resists desiccation; predominantly scavengers; microorganisms and organic detritus
6. Class Echinoidea
a. Echinoid Biology
- globe-shaped armored animals with a subdermal skeleton composed of many plates and with
movable spines (for locomotion and defense)
- regular echinoids (Ordovician-Recent) with anus located at the "north pole" of the sphere within
a circlet of plates; vagrant benthonic
- irregular echinoids (Jurassic-Recent) with anus lying outside of and posterior to the ring of
plates; most were fossorial (burrowing) forms
PALEO LECTURE, PAGE 87
b. Echinoid Biostratigraphy
- Paleozoic echinoids are rare as fossils and are of little biostratigraphic use; all echinoids except
cidaroids became extinct at the end of the Paleozoic
- during Jurassic regular echinoids developed longer spines and more tube feet, increasing their
ability to respire and gather food; development of fossorial (digging) adaptations during the
Jurassic and Cretaceous resulted in an adaptive radiation with many new forms evolving
(therefore echinoids may be utilized for biostratigraphic studies within rocks of Jurassic,
Cretaceous and Tertiary age)
XXI. Nets, Wrigglers, and "Teeth" Without Jaws
A. Phylum Hemichordata
- often placed within the Phylum Chordata but do not appear to be closely related to true
chordates; embryo and early larva of hemichordates and echinoderms similar (deuterostomes);
suggest common origin
- formerly believed to possess a notochord but structure is actually an elongate tubular pouch
connected to the digestive tract; but most with paired gill slits
- includes the modern pterobranchs and acorn worms; only important fossil representatives are
the graptolites (are tentatively considered hemichordates)
1. Class Graptolithina
- fossil colonial marine organisms; proteinaceous skeleton; formed complexly branched colonies
or simple linear series of interconnecting tubes; zooids commonly in linear series or in series of
clusters, connected to each other by stolons; Cambrian to Pennsylvanian; approximately 240
genera and 1800 species
a. Morphology of Graptolites
Aperture - opening of one of colonial cups or tubes
Autotheca - largest of three cups or tubes produced by each act of budding
Basal Disk - chitinous patch at end of nema for attachment of colony
Bitheca - small cup or tube accompanying autotheca
Nema - chitinous threadlike tube which terminates in basal disk at one end and sicula at other in
dendroids; in graptoloids was threadlike rod by which colony was suspended
Rhabdosome - entire graptolite colony, developed by budding from a single sicula
Sicula- cup belonging to initial zooid of colony
PALEO LECTURE, PAGE 88
Stipe - branch of colony, consisting of overlapping thecae
Stolon - chitinoid tube extending through successive stolothecae of a stipe, and sending off
branch stolons to base of each autotheca and bitheca
Stolotheca - cup or tube of each set of three thecae from which a succeeding generation of three
thecae is budded
Theca - any cup or tube of colony that housed the zooid
Zooid - individual graptolite animal
b. Classification
- 6 orders (Dendroidea, Camaroidea, Crustoidea, Stolonoidea, Tuboidea, Graptoloidea);
Dendroidea and Graptoloidea most important
b1. Order Dendroidea
- attached, branching graptolites characterized by two sizes of thecae (larger autothecae and
smaller bithecae); in most species, stolons included hard, black, organic substance, probably
proteinaceous; most lived in relatively shallow waters; Middle Cambrian to Pennsylvanian;
approximately 30 genera
b2. Order Graptoloidea
- planktonic graptolites characterized by one type theca (equivalent ot autotheca of other
graptolites) on few stipes; in some colonies autothecae of progressively different shapes and sizes
along stipes; Ordovician to Early Devonian; about 185 genera
B. Phylum Chordata - Subphylum Vertebrata (Craniata) - Class "Agnatha" - Subclass Conodonta
- conodonts were previously placed within their own phylum (the Conodonta), but are now
typically considered to represent a member of the jawless fishes; preservation of soft-bodied
specimens indicate that they were elongate, eel-like animals
1. Relationships of Conodonts
- conodont chordate synapomorphies include the presence of a notochord, dorsal nerve cord,
myomeres (muscle blocks along the length of the body), a tail, and a midline tail fin
- Conodont vertebrate synapomorphies include the presence of a cranium in front of the
notochord, paired sense organs, extrinsic eye musculature (absent in hagfishes), and a caudal fin
with radial supports
- based on the presence of dentine- and enamel-like tissues, eye musculature, etc. the conodonts
appear to be more derived vertebrates than either hagfishes or lampreys
- see below for more characteristics of the Chordata, Vertebrata, etc.
2. Morphological Groups of Conodont elements
- skeletal parts consist of microscopic mineralized Elements arranged in patterns (Apparatuses);
PALEO LECTURE, PAGE 89
microwear studies indicate that these hard parts were used for securing and chopping up prey;
more or less complete apparatuses are termed Natural Assemblages
a. Cone-shaped (Coniform) Elements
- cone-shaped structures consisting of a base and a cusp
b. Blade-shaped (Ramiform) Elements
- structures that include a main cusp flanked by posteroanterior and/or laterally directed processes
that commonly possess denticles
c. Platform-shaped (Pectiniform) Elements
- structures that commonly bear denticles on platforms of laterally expanded processes
3. Classification of Conodonts (based on isolated elements)
a. Order Paraconodontida
- typically coniform with a deep basal cavity, a few widely-spaced lamellae (layers observed
within skeletal cross-sections), considerable organic matter within the skeleton; approximately 15
genera; Late Proterozoic - Mid Ordovician
b. Order Conodontophorida
- with coniform, ramiform, and pectiniform elements; numerous closely-spaced lamellae and
nonlaminated, often bubble-like, lighter-colored material (white matter) between and cutting
across the lamellae; basal plate present; elements often ornamented; approximately 215 genera;
Cambrian - Upper Triassic
XXII. From Starfish to Fish, Lords of the Water
Subphylum Vertebrata
A. Chordates
1. Characteristics
- possess a notochord, a dorsal hollow nerve cord with a shared developmental pattern, an
endostyle organ (equivalent to the thyroid gland of vertebrates), and a tail for swimming (a tail is
a distinct region developed behind the anus)
2. Origin of the Chordates
- Walter Garstang (1928) said that higher chordates evolved from sea squirt larvae through
paedomorphosis (adults retaining juvenile characteristics) but recent molecular data suggests that
sea squirts are a separate line of evolution
- modern hypotheses state that chordates are derived from hemichordates (both with ciliated gill
slits and giant nerve cells not seen in echinoderms) OR from calcichordates (based on
interpretation of fossils) OR that hemichordates and echinoderms are sister groups (the
PALEO LECTURE, PAGE 90
Ambulacraria) and urochordates, cephalochordates and vertebrates are a clade (with
cephalochordates closer to vertebates than urochordates (based on morphological and molecular
data)
B. Vertebrate Characteristics
1. Shape
- are bilaterally symmetrical with long axis of body usually in a horizontal position; tendency of
fish and other swimming vertebrates towards a fusiform shape
2. Cephalization
- tendency to concentrate sensory organs on the anterior ("front") end
3. Notochord
- long, rod-shaped anti-telescoping structure below nerve tube found in some lower vertebrates;
not preserved in the fossil record
4. Cartilage and bone - makes up the skeletal system
a. Cartilage
- soft, translucent material confined to deeper layers of body; capable of growth; some lower
vertebrates with cartilage only but usually not preserved in the fossil record
b. Bone
- distinguished from cartilage because bone has irregular, branching cell spaces and is much
stronger than cartilage; not capable of "expansional" growth
5. Axial Skeleton
- vertebrae constituting the backbone
6. Appendicular Skeleton
- consist of both unpaired and paired appendages and their supporting girdles
a. Limb girdles - support the limbs
b. Fin types
Median fins - unpaired fins
Dorsal fins - on upper side of body
Anal fin - on ventral (lower) portion of body posterior to the anus
Caudal fin - the tail fin; there are several different types: Heterocercal (body containing backbone
tips up posteriorly and the fin is developed below it; probably gave rise to all other caudal fin
PALEO LECTURE, PAGE 91
types); Reversed Heterocercal (Hypocercal) tail (posterior tip of body tilted down and fin
developed above it); Diphycercal tail (symmetrical tail in which the vertebrae extend outward to
the tip); Homocercal tail (derived fish tail type with the tail symmetrical and with abbreviated
vertebrae)
Paired fins- occur in pairs (of course); include Pectoral fins (found just posterior to the gill
region); Pelvic fins (found usually at posterior end of trunk in front of anal opening); the purpose
of fins (except caudal) is for steering and balancing
7. Branchial Arch System
- cartilaginous or bony bars situated between gill openings to support the gill musculature and
stiffen the gill region
8. Skull
- embryo in every vertebrate has a braincase that articulates with the vertebral column
- nasal capsules protect nostrils; hollows in sides receive eyes; posterior portion encloses the otic
(ear) capsules
9. Denticles
- derived from the deeper layers of the skin and found in many fish
- usually hollow, cone-shaped structures; probably modified to form fin spines in sharks, etc.
10. Teeth
- specialized dermal denticles present in "all" jawed vertebrates
C. The Record of the earliest Vertebrates
1. Middle Early Cambrian (525-520 Ma)
- Chengjiang Fossil Site, Yunnan Province, southwest China with mostly arthropods but also
possible basal deuterostomes (e.g., the Vetulicolians and Yunnanozoons) and the first fishes
(Myllokunmingia, Haikouichthys and Zongjianichthys)
2. Late Cambrian Vertebrates
- conodonts were the earliest vertebrates with hard tissues
- another group of vertebrates is indicated by isolated pieces of dermal armor (Anatolepis) from
Wyoming and Greenland (this dermal armor is made from apatite, which is characteristic of
vertebrates)
D. Agnathans
- jawless vertebrates; paired fins absent or poorly developed; primitive ear region
1. Classification
There is considerable debate. I have included a common classification here with some
PALEO LECTURE, PAGE 92
synonyms:
Phylum Chordata
Subphylum Vertebrata (Craniata)
Class "Agnatha" (= Cyclostomata)
Subclass Myxinoidea
Subclass Petromyzontida (= Petromyzonida; Petromyzontiformes)
Subclass Conodonta
Subclass Pteraspidomorphi (= Diplorhina sensu stricto)
Order Astraspida
Order Arandaspida
Order Heterostraci (= Pteraspida)
Subclass Cephalaspidomorpha (= Monorhini, Monorhina)
Order Osteostraci (= Cephalaspida)
Order Galeaspida
Order Pituriaspida
Subclass incertae sedis (i.e., we don't know the relationships of the following 2 groups)
Order Anaspida
Order Thelodonti (= Coelolepida; sometimes placed within the pteraspidomorphs)
2. "Cyclostomes"
- polyphyletic grouping of the modern lampreys (Petromyzontida) and hagfishes (Myxinoidea);
semiparasitic animals with no jaws; Upper Mississippian - Present
3. Conodonts
- see discussion above
4. Pteraspidomorphs
- often includes the Astraspida and Arandaspida (Ordovician groups represented by pieces of
dermal armor), the heterostracans, and sometimes includes the thelodonts
- with paired nasal sacs and openings; typically one pair of gill openings; skull not forming
complete head shield
Common types of Pteraspidomorphs include:
a. Heterostracans
Range: Ordovician - Upper Devonian (earliest undisputed vertebrates)
Characteristics: mouth usually anterior and ventral with the development of long, narrow Oral
Plates (have small tiny backward-pointing denticles that were probably used for capturing prey);
may have given rise to other agnathans but probably too specialized to give rise to jawed fishes
5. Cephalaspidomorphs
- include the Osteostraci, the Galeaspida and the Pituriaspida
a. Characteristics
PALEO LECTURE, PAGE 93
- with massive head shield that covered gills dorsally and with ventral placement of mouth and
gill openings
- with single, medially-placed nasohypophyseal opening
b. Osteostracans (Tremataspids + Cephalaspids)
- the most common cephalaspidomorphs
Range: Upper Silurian to Upper Devonian, mainly in western Laurasia
Characteristics: usually small fish with undivided bony shield which extends down the body;
head dorsoventrally compressed; dorsal eyes and with dorsal and lateral fields ("electric" or
pressure-sensitive "sensory" organs?) on top of head; heterocercal tail; believed to be bottom
dwellers and "mud grubbers"
6. Agnatha incertae sedis (Agnathans of uncertain affinities)
a. Anaspids
Range: Upper Silurian-Upper Devonian
Characteristics: small, streamlined (fusiform), laterally-compressed fishes; eyes laterally placed;
mouth terminal and in form of oval, vertical slit for filter feeding(?); hypocercal tail
b. Thelodonts (Coelolepids)
Range: Lower Silurian?; Upper Silurian-Middle Devonian
Characteristics: small fish with tiny cone-like scales (denticles; used in classification); eyes far
apart and lateral; mouth ventral (but nearly terminal); often with hypocercal tail
- some specimens from the Devonian with a deep, laterally-compressed body, a forked tail and
large stomach
E. Evolution of Jaws and Fins
1. Origin of Jaws
a. Older theories state that jaws may have been derived from gill arch supports
- but problem is that gills in lampreys develop medially to the supporting skeleton, whereas in
gnathostomes they develop laterally and jaws develop embryologically from the neural crest, not
from gills
b. Modern embryological studies indicate that once bones around eyes are formed, a series of
connector genes may have begun making a lower jaw cartilage, perhaps to strengthen the existing
mouthparts
2. Types of Jaw Articulations
a. Autostyly - articulation formed by jaws without aid from gill arch behind them; found in
most placoderms; some acanthodians
b. Holostyly - fusion of upper jaws to braincase; chimaeras, lungfish
PALEO LECTURE, PAGE 94
c. Amphistyly - first gill arch becomes enlarged and aids in propping the jaws on braincase;
found in some placoderms, some acanthodians, early sharks, early osteichthyes
d. Hyostyly - first gill arch bears main burden of jaw support; found in modern sharks and
higher actinopterygians
3. Fins
a. Early fins with spines, flaps or folds for stability; later types with two paired fins (pectorals
and pelvics) articulating with girdles
b. Origin of Paired Fins
Fin-Spine Theory - primitive fin type was skeleton with long central axis bearing side branches;
therefore primitive fin had a narrow base developed around a movable spine
Fin-fold Theory - fins originated as lateral folds from body walls; pectoral and pelvic fins
originated by subdivision of this fold; therefore primitive fin had broad base; most widely
accepted theory but fin origins may be combination of "fin spine" and "fin fold"
F. Placoderms
1. Classification
Phylum Chordata
Subphylum Vertebrata (Craniata)
Infraphylum Gnathostomata
Class Placodermi
Order Antiarchi
Order Arthrodira
2. Characteristics
typically dorsoventrally compressed fishes with head and trunk shields (in advanced types shields
connected by ball-and-socket articulation)
- Range: Devonian to Lower Mississippian; placoderms had no descendants
- Paleoecology: freshwater or marine; usually benthonic and not very powerful swimmers
- include the large carnivorous Arthrodires and the "arthropod-like" mud-grubbing Antiarchs
G. Acanthodians
1. Classification
Phylum Chordata
Subphylum Vertebrata (Craniata)
Infraphylum Gnathostomata
Class Acanthodii
PALEO LECTURE, PAGE 95
2. Characteristics
- small fusiform fish; all fins except caudal with spines on anterior edge; heterocercal tail
- Range: Late Ordovician to Lower Permian
H. Chondrichthyans
- sharklike fishes
1. General characteristics
Range: Upper Ordovician/Silurian? (based on isolate scales and teeth) to Recent
- cartilaginous (cartilage consists of prismatic structure; first preserved prismatic cartilage is
Early Devonian age); skin covered with dermal denticles including placoid scales, teeth, claspers
and fin spines (histology of teeth is sometimes used in classifications)
2. Classification
Here's a common classification but there are others:
Class Chondrichthyes
Phylum Chordata
Subphylum Vertebrata (Craniata)
Infraphylum Gnathostomata
Subclass Elasmobranchii
Infraclasses unnamed for following groups:
Order Cladoselachida
Order Symmoriida
Order Eugeneodontiformes (= Eugeneodontida) - includes the caseodonts and
edestids
Order Petalodontiformes (= Petalodontida)
Infraclass Euselachii
Order Xenacanthiformes (Xenacanthida)
Order Ctenacanthiformes
Order Hybodontiformes
Cohort Neoselachii
Subclass Subterbranchialia
Order Iniopterygiformes (Iniopterygia)
Superorder Holocephali
Order Bradyodontida -includes the Suborder Chimaerina
3. Subterbranchialians
Range: Mississippian to Recent
Characteristics of Subterbranchialians: shoulder girdle located directly behind head with the
branchial basket (gill area) crowded into restricted space anterior to shoulder and mostly beneath
the skull
- almost all were probably sluggish, vagile benthonic animals including the bizarre Iniopterygians
PALEO LECTURE, PAGE 96
and the Holocephalians (includes the modern ratfish)
4. Elasmobranchs
- with branchial basket expanded posteriorly and lying mostly behind the skull; gill pouches open
separately to outside and gill arches widely spaced
- approximately 10 orders; the most important are:
a. Symmoriids
- best known Paleozoic sharks
Range: Upper Devonian to Pennsylvanian; North America, Europe
Characteristics: cladodont dentition, a short blunt "snout"; some with wierd dorsal fin brushes
(for sexual display?)
b. Eugeneodonts
Range: Upper Devonian to Triassic
Characteristics - symphysial teeth tend to form elaborate cutting devices (edestid, caseodontid
and helicoprion-type sharks) with whorl-shaped replacement; lateral teeth usually form crushing
surfaces; with highly specialized tail fins in which the neural and haemal arches modified to form
a number of large cartilage plates; pelvic girdles and fins are completely reduced
c. Euselachians
- include the xenacanths and the "modern shark" groups; united in resemblances in their fin
structure
c1. Xenacanths (pleuracanths)
Range: Upper Devonian to Upper Triassic; North America, South America, Europe, Australia,
India
Characteristics : freshwater (?) sharks with fusiform body; teeth with two or three pointed cusps;
two anal fins; diphycercal caudal fin
c2. Ctenacanths, Hybodonts and Neoselachians
Range: Devonian to Recent
Characteristics: primary character is two dorsal fins with spines coated with an enameloid-like
dentine; skin covered with placoid scales
- improvements from primitive to modern sharks include shift from amphistylic to hyostylic jaw
articulation (with shortened jaws that pivot on modified first gill support; forms protrusion
mechanism); improvements in smell, large brains, calcified vertebral centra; three basal elements
in pectoral fins; neoselachian sharks include modern sharks, skates and rays
I. Actinopterygians
- bony fish (Osteichthyes) that differ from sarcopterygians in the presence of fin rays (bony, rodlike fin supports)
PALEO LECTURE, PAGE 97
1. Range: (Upper Silurian?) Lower Devonian-Recent
- found in both freshwater and marine environments from the Devonian to Recent
2. Classification and Origin
- possibly originated from the acanthodians
- taxonomy of actinopterygians is a mess with numerous controversies
- Psarolepis, from the Upper Silurian/Lower Devonian of China and Vietnam, shows
characteristics of both actinopterygians and sarcopterygians, and is classified as either a basal
actinopterygian or sarcopterygian on cladograms
a. A common classification is as follows (but there are others):
Phylum Chordata
Subphylum Vertebrata (Craniata)
Infraphylum Gnathostomata
Class Osteichthyes
Subclass Actinopterygii
Superdivision Chondrostei
Superdivision Neopterygii
Division Ginglymodi
Division Halecostomi (Ginglymodi + Halecomorphi = "Holosteans")
Subdivision Halecomorphi
Subdivision Teleosti
3. Evolution of the Major Morphological Features of the Actinopterygians
- mostly deal with feeding and locomotory systems
- I think it is a great example of DeBeer's concept of Mosaic Evolution
a. The Locomotor System
- act in propulsion, steering and hydrostatic adjustment
a1. Caudal Fin
- primitive is heterocercal and typically with a hypochordal (lower) lobe (found in chondrosteans)
- homocercal tail (with a symmetric caudal) found in some holosteans and in teleosts (probably
accompanied by greater efficiency of swim bladders and reduction of fish's weight by reducing
scales)
a2. Dorsal and Anal Fins
- Chondrosteans with stiff, triangular and broad-based dorsal and anal fins; fin rays numerous
and closely set and were strong but inflexible)
- primitive neopterygians ("holosteans") with fin rays becoming fewer, lighter, and therefore fins
were more flexible and mobile
- Teleosts developed stiff, pointed spines (especially in the dorsal fins)
a3. Paired fins
PALEO LECTURE, PAGE 98
Structural changes - primitive actinopterygians with triangular, broad-based paired fins with
numerous closely-spaced fin rays, with moderate to large pectoral fin and with small anal fin;
derived characteristics include narrow fin bases, reduction in number and wider spacing of fin
rays; teleosts developed spines
Position changes of paired fins - common derived condition is forward movement of pelvic fins
accompanied by tendency for pectoral fin to lie higher on the lateral body wall (good for intricate
manuevering)
a4. Vertebral Column and Ribs
- Chondrosteans with large, unrestricted notochord; centra generally absent; neural and haemal
arches well developed
- Teleosts with vertebrae consisting of biconcave centrum and with neural and haemal arches
fully ossified
a5. Scales
- general scale morphology and histology may be very useful in the classification of the
actinopterygians
Ganoid scales - large, thick rhomboidal scales with "peg and socket" articulation characteristic of
primitive actinopterygians; characterized by presence of a thin enameloid (= ganoin) layer on
outer surface
Cosmoid scales - derived(?) scale which consists of three parallel layers; possibly derived from
ganoid scales by reduction of ganoin; found in primitive crossopterygians and lungfish
Cycloid scales - lost ganoin and cosmine layers, leaving only the innermost bony layer
(isopedin); thin circular scales with growth rings found in many advanced actinopterygians
Ctenoid scales - very much like cycloid scales in structure but with ctenii (barbs) on the scales;
found in many derived actinopterygians
a6. Body Form
- primitive actinopterygians typically fusiform (chondrosteans and holosteans typically
conservative but some types had elongate or deep bodies)
- teleosts with a wide variety of body shapes
b. Feeding Systems
- many skull and jaw modifications due to feeding and respiratory modifications
- trend toward kinetic head skeletons (composed of several mobile units that can move against
each other)
b1. Chondrostean stage
- skull bones supporting jaw (suspensorium) strongly oblique; primary upper jaw bone (maxilla)
is firmly joined to other skull bones; branchiostegal rays (elongate bones on posteroventral part
of skull) numerous, closely spaced, small and all similar; cheek region completely covered (all of
PALEO LECTURE, PAGE 99
these features were for bracing the jaws)
b2. Primitive Neopterygian ("Subholostean/Holostean") Stage
- suspensorium of jaw becomes more nearly vertical; specialized jaw support (the symplectic)
forms; maxilla becomes separated from other skull bones but still retains teeth; number of
branchiostegal rays decreases (dorsal-most branchiostegal enlarged to anchor the muscle which
depressed the lower jaw); all of these features greatly increased feeding effectiveness by
increasing the strength of the bite
b3. Teleost Stage
- upper anterior jaw element (premaxilla) freed and becomes primary tooth-bearing element in
the upper jaw (became protrusible in many teleosts); maxilla freed so that it could be pulled
down and forward by the lower jaw as the mouth opened; these features were developed for
"suction feeding"
J. Sarcopterygian Fishes
- bony fish (Osteichthyes) with fleshy lobe fins, a squamosal bone is present on the skull, and a
cosmine layer is present on the scales and bones
1. Classification
- relationships of lungfishes, coelacanths and their Paleozoic relatives is controversial, with
several competing cladistic analyses
The following is one classification scheme with several others available:
Phylum Chordata
Subphylum Vertebrata (Craniata)
Infraphylum Gnathostomata
Class Osteichthyes
Subclass Sarcopterygii
Order Dipnoi
Infraclass Crossopterygii
Order Actinistia
Infraclass Tetrapodomorpha
Superorder Osteolepidida
2. Dipnoans
- the lungfish
a. Range: Lower Devonian to Recent
b. Characteristics:
- all dipnoans with holostylic jaw (fused to the braincase); they have no marginal teeth; the
external nasal openings are ventral in position; No choanae (internal nares) are present; all have
lobate fins
- most with diphycercal tail and with a continuous dorsal, caudal and anal fin; dentition usually
PALEO LECTURE, PAGE 100
consists of crushing toothplates
c. Paleoecology
- modern species are found in freshwater but extinct types inhabited a wide variety of
environments
- essentially all were bottom dwelling omnivores
- older types seem to have relied on lungs
- burrows (for aestivation during dry seasons, where they can survive in a semi-inanimate state in
a flask-shaped, mucus-lined pit) are found from the Devonian to Recent
3. Coelacanths (Actinistia)
- coelacanths and osteolepiforms are bony fish with two dorsal fins, lobate paired fins, and
cosmoid structure of the scales and dermal bones; most important distinguishing feature is
braincase division into an anterior (ethmo-sphenoid) and posterior (otico-occipital) parts with an
intracranial joint between them; small plates surround eye
- predominantly predatory fishes and mainly relied on sense of smell (with small eyes)
- fossils range from Middle Devonian to Upper Cretaceous (both marine and freshwater); with
one (or possibly two) living marine species (Latimeria chalumnae)
- features differing from osteolepiforms include: braincase juncture position different from
osteolepiforms; no maxilla; upper jaw attached to braincase
4. Osteolepiforms ("Rhipidistia", in part)
- important fish since they (or a closely related group) gave rise to the amphibians
- large, voracious fish
Range: Middle Devonian to Lower Permian
Characteristics: most differ from coelacanths in the arrangement and number of dermal bones in
the head (in fact the bones in the heads of osteolepiforms are largely homologous to those of
primitive tetrapods); usually possess choanae (internal nares)
- other important features which link the osteolepid fishes to early tetrapods include
labyrinthodont teeth (with infolded plicidentine), single basal elements in the pectoral and pelvic
fins (homologous to the humerus and femur) which articulate with the limb girdles; pairs of
radials articulate with the single basals (these pairs are homologous to the radius and ulna or tibia
and fibula of tetrapods); axial skeleton is like rhachitomous type found in some early tetrapods
(consists of a wedge-shaped intercentrum and small paired pleurocentra)
XXIII. The Greening of the Land
- included here is a discussion of the Kingdoms Fungi and Plantae (Metaphyta)
A. Kingdom Fungi
- heterotrophs that secrete enzymes able to break down external food sources into molecules
small enough to be absorbed by cells (extracellular digestion and absorption); are a major group
of decomposers; Saprobic/saprophytic types feed on nonliving organic matter; parasitic types
feed on living organisms
PALEO LECTURE, PAGE 101
1. Classification
- the Fungi is probably a polyphyletic group and therefore is invalid; includes the Divisions
Gymnomycota (slime molds), Mastigomycota (flagellate fungi or phycomycetes; including the
classes Oomycetes and Chytridomycetes) and the Amastigomycota (nonflagellated fungi or true
fungi; including the classes Zygomycetes, Ascomycetes and Basidiomycetes)
- there are about 250 genera and 500 species of fossil fungi, mostly from Cretaceous and Tertiary
2. Evolution and the Fossil Record
- the Ascomycetes and Basidiomycetes evolved in Cambrian and Ordovician seas as
heterotrophic fungi living on algae
- during the Silurian, fungi moved to land environments to live as saprophytes and parasites on
the early land plants
- all classes of fungi were present by the end of the Pennsylvanian
- fungi evolved and radiated into new environments pioneered by the flowering plants during the
Cretaceous and Tertiary; this adaptive radiation is probably due to coevolution of fungi with the
evolving angiosperms
B. Kingdom Plantae - Classification
*Subkingdom or Division Bryophyta (mosses, liverworts, and hornworts)
*Subkingdom or Division Tracheophyta (vascular plants)
Class Rhyniopsida (primitive vascular plants)
Order Rhyniales
Class Psilopsida (whisk ferns)
Class Zosterophyllopsida (ancestors of microphyllous plants)
Order Zosterophyllales
Order Asteroxylales (prelycopods)
Class Lycopsida (club mosses and their relatives)
Order Drepanophycales
Order Protolepidodendrales
Order Lycopodiales
Order Selaginellales
Order Lepidodendrales
Order Isoetales
Class Trimerophytopsida (ancestors of megaphyllous plants)
Class Sphenopsida (horsetails and their relatives)
Order Hyeniales
Order Pseudoborniales
Order Sphenophyllales
Order Equisetales
Class Filicopsida (ferns and their relatives)
Order Cladoxylales
Order Stauropteridales
Order Zygopteridales
PALEO LECTURE, PAGE 102
Order Ophioglossales
Order Marattiales
Order Filicales
Order Salviniales
Order Marsileales
Class Progymnospermopsida (ancestors of gymnosperms)
Order Aneurophytales
Order Archaeopteridales
Order Protopityales
Class Gymnospermopsida (plants with naked seeds)
Order Pteridospermales
Order Cycadales
Order Cycadeoidales
Order Caytoniales
Order Glossopteridales
Order Pentoxylales
Order Czekanowskiales
Order Gnetales
Order Ginkgoales
Order Cordaitales
Order Voltziales
Order Coniferales
Order Taxales
Subdivision Angiospermophytina (flowering plants)
Class Magnoliopsida/Dicotyledonae (dicotyledons)
Class Liliopsida/Monocotyledonae (monocotyledons)
* Depending upon the scientist, the taxonomic category will vary. Some paleobotanist's
"Subkingdom" is another's "Division", or "Division" to one may be a "Class" to another, etc. (see
classifications below for comparison)
C. Origin of Land Plants (Kingdom Plantae) is Monophyletic
- evolved from the Chlorophyta (grass-green algae)
Synapomorphic characters include:
1. have chlorophyll a and b
2. store true starch
3. have cellulose in cell walls
4. protostele with xylem forming core (xylem forms pipelines for conducting water and
dissolved minerals), phloem on outside (phloem is the food-conducting tissue; found in roots of
most vascular plants; stems of many psilopsids, lycopods, sphenopsids and ferns)
PALEO LECTURE, PAGE 103
5. life cycles similar (alternation of generations, etc.)
D. Characteristics of the Kingdom Plantae (*prevents desiccation in terrestrial environments)
1. fertilized egg develops into an embryo which is enclosed within a protective covering*
2. protection of spores and pollen grains by tough wall impregnated with sporopollenin*
3. Parenchyma Tissues - continue to live after maturity; may combine with other cells to form
complex tissues*
4. Waxy layers on leaves and branches*
5. Guard cells of stomata (openings in the leaves)*
6. Alternation of Generations
- multicellular gamete-producing organisms (gametophytes) alternate in the life cycle with
multicellular spore-producing organisms (sporophytes)
E. Classification and Characteristics of the Kingdom Plantae
1. Subkingdom Bryophyta
- includes mosses, liverworts and hornworts (may be a polyphyletic group and some propose
establishment of three separate Divisions)
- no stiffened vascular tissue for conducting water and nutrients; gametophytes most important
phase of sexual reproduction
- features useful for land-dwelling existence include presence of water-conserving cuticle on the
above-ground parts, presence of protective cellular jacket around the sperm- and egg-producing
parts of the plant to keep them from drying out, and the sporophyte begins early development as
an embryo inside the tissues of the female gametophyte
- poor fossil record (Devonian - Recent)
2. Subkingdom Tracheophyta
- vascular plants [with conducting cells (xylem and phloem) for transporting water and nutrients];
usually possess roots, stems and leaves
- with approximately 11 to 13 Divisions
The most important divisions are:
a. Division/Class Rhyniophyta (Rhyniopsida)
- Middle Silurian to Middle Devonian
- oldest-known vascular plants (Middle Silurian of Ireland); best fossils from the Rhynie Chert
(Lower Devonian, Scotland); Examples = Rhynia, Cooksonia
- no leaves or roots (therefore with photosynthesis occurring in the outer cells of the stem); with
PALEO LECTURE, PAGE 104
dichotomous branching of the stems (branch by producing two equal segments); stems capped by
spore-bearing cases (sporangia); spores are homosporous (with one type of spore) and spore is
trilete (round or triangular, with three folds on it)
b. Division/Class Psilopsida
- "whisk ferns"; the living whisk broom-looking genus Psilotum is very similar to the
Rhyniophyta with three-dimensional dichotomous branching and low degree of organ
differentiation with roots and vascularized leaves absent
- But sporangia are borne terminally on short lateral axes (whereas on Rhyniopsida are terminal
on the axial, or main, portions of the plant)
c. Division/Class Zosterophyllopsida
- Uppermost Silurian through Middle Devonian; Example = Zosterophyllum
- ancestors of microphyllous plants
- also leafless and branched dichotomously, but sporangia are borne along the sides of the axis;
sporangia kidney-shaped and attached to a short stalk; branches fork into two axes, one grows
upward and one downward ("H-branched", probably allowed plant to spread outward from a
center and to be attached to the soil as it grew out)
d. Division/Class Lycophyta (Lycopodophyta, Lycopsida)
- Devonian-Recent; includes the modern club mosses and quillworts; also arborescent (tree-like)
lycopods up to 40 meters high (Order Lepidodendrales; Devonian- Pennsylvanian; dominated
Carboniferous coal swamps)
- evolved from the Rhyniopsida
- have true roots (or at least root-like organs), stems and often with small leaves with a single
strand of vascular tissue and NO leaf gap ("microphylls"); leaves on trunk in pits (leaf
cushions/bolsters) and arranged in spirals
- often with cone-shaped clusters of leaves bearing spore sacs (each cluster is a Strobilus); spores
dispersed from spore sacs and germinate to form small, free-living gametophytes; modern types
require water in which sperm can swim to the eggs (therefore restricted to wet habitats)
- Examples = Lepidodendron, Lepidophloios, Sigillaria (stems/trunks), Stigmaria (roots or
rhizophores), Lepidophylloides (leaves)
e. Division Sphenophyta (Sphenopsida)
- include the modern horsetails and several extinct groups (Devonian- Recent)
- with scale-like, small leaves arranged in whorls around an above-ground, bamboo-like jointed
(with nodes and internodes) photosynthetic stem that is hollow inside; walls of stem cells contain
silica, so stems often "gritty" (hence the name "scouring rushes"); spores form inside coneshaped clusters of tiny branches at the shoot tips and are dispersed by air currents; spores must
germinate within a few days to produce gametophytes (free-living plants)
- are typically found in swamps, moist woodlands, and along lake edges
- common fossils include Calamites (a Pennsylvanian-age arborescent sphenopsid; some
members up to 15 meters or more in height) and Annularia (leaf whorls)
f. Division Filicinophyta (Filicopsida, Pteridophyta)
PALEO LECTURE, PAGE 105
- include ferns and their allies (Upper Devonian - Recent)
- large, complex leaves [megaphylls; with leaf gaps (spaces developed where the leaf stalk
(petiole) joins the vascular cylinder of the twig)]; fern leaves (fronds) usually featherlike with
blades finely divided into segments (leaf pinnately compound, with the leaflets arranged along
the sides of a common axis) and develops rachis, pinna and pinnules; immature fronds unroll
(circinate) in most members; often with clusters of spore cases (Sorus) on leaf undersides, with
sporangium snapping open at dispersal time to cause the spores to catapult into the air;
germinating spore develops into a small gametophyte
- Tree ferns were large, arborescent ferns (Mississippian - Permian) found in coals swamps (Exs.
= Psaronius, Pecopteris)
- arborescent lycopods, sphenopsids and tree ferns became extinct when the Late Paleozoic coal
swamp environment declined, probably due to climate changes resulting from the formation of
Pangaea
g. "Gymnosperms"
- probably a polyphyletic group; includes coniferophytes, pteridospermophytes, cycadophytes,
cycadeoidophytes, ginkgoes, and four plant groups of uncertain affinities
- gymnosperms (and angiosperms) are characterized by seeds; typically formed by fusion of egg
and sperm nuclei; then develop into ripened ovules (= seeds)
- gymnosperms have no flowers and seeds are not fully enclosed (gymnosperm means "naked
seed")
g1. Division/Class/Order Pteridospermophyta
- include the "Seed Ferns"; Upper Devonian - Jurassic
- with fern-like compound leaves (Fronds) but gymnosperm-like seeds and wood
- Exs. = Alethopteris, Neuropteris, Medullosa (trunk) and possibly Glossopteris (leaves)
g2. Division/Class/Order Cordaitales
- cordaites; Pennsylvanian to Middle Permian; tall trees about 15 to 30 meters high
- leaves often sword- or strap-shaped with dichotomous venations (with forking leaf veins);
leaves were borne spirally in a crown near the top of the plant
- petrified stems with pith area crossed by strands of parenchyma cells (the tissue that makes up
the bulk of the fleshy plant parts) separated by air spaces
- seed-bearing cone-like structures and pollen-bearing cones borne on special small branches
g3. Division/Class/Order Coniferales
- conifers (Exs. = pines, spruces, firs, hemlocks, junipers, cypresses, redwoods); Triassic-Recent
- woody trees and shrubs with needlelike or scalelike leaves; most are evergreens (shed leaves
throughout year but retain enough of them to distinguish them from deciduous trees); conifers
have Cones (cone-shaped clusters of modified leaves bearing the sporangia); often two kinds of
cones (male cones bear microspores and female cones develop megaspores); seeds develop on
the shelf-like scales of the female cones
g4. Division/Class/Order Ginkgoales
- ginkgos (?Permian; Triassic-Recent; one recent species, the "maidenhair tree")
PALEO LECTURE, PAGE 106
- often conifer-like trees with a main trunk bearing branches with axillary long and short shoots;
leaves are usually fan-shaped; some leaves are deeply lobed, others are not; venation of the
leaves typically parallel, although each vein is divided
g5. Divisions/Classes/Orders Cycadophyta (cycads) and Cycadeoidophyta (cycadeoids)
- cycads (Permian-Recent) and cycadeoids (Triassic-Cretaceous) are often difficult to distinguish
as fossils (both often form shrubby or tree-like plants with pinnate, strap-like, palm-like leaves
and similar wood)
- but cycads have male and female cells in distinctly different cone-like structures whereas in
cycadeoids the male and female cones are very similar
XXIV. Amphibians, Ancient and Modern
A. Ecology and Origin of Tetrapods
1. The "Classic" Theory
- land invasion during Late Devonian when ponds and streams dried out periodically
- evidence includes Devonian "redbeds" (wet-dry seasonality); also earliest amphibians
(Ichthyostega) were fully terrestrial (?)
2. Occupancy of land took place under warm, moist climates
- low oxygen content in the water, population pressures (seeking food, competition for space,
breeding sites, escape from predators or egg-eaters)
- evidence from studies of modern air-breathing fish and amphibians and contradictory evidence
about the geological conditions of the Devonian
3. Amphibians originated in the water and were "preadapted" to a life on land
- limbs, hearing, air-breathing and feeding modifications related to life in warm, shallow water
with low oxygen content
- terrestrial radiations came much later from the various lines of aquatic tetrapods
B. "Amphibians"
- the earliest tetrapods (four-footed creatures) are from Upper Devonian rocks
- some cladistic classifications state that the "Amphibia" should only include the modern
lissamphibians
1. Origins and Adaptations
a. derived from the osteolepiform fishes, efficient air breathers which lived in warm, shallow
water sometimes low in oxygen
b. lungs became more efficient (but gill-breathing retained in immature and larval stages of
primitive types)
c. evolution of paired appendages (due to substrate locomotion?); as air breathing became more
PALEO LECTURE, PAGE 107
efficient the pectoral fin was used to lift the head out of water; fins became the tetrapod limbs
with the loss of the fin rays
2. Primitive Amphibian Structure
a. External shape and form
- typically the small and primitive types tend to be relatively high and round-bodied
- bony scales reduced but ancient types often retained V-shaped ventral armor
b. Axial Skeleton
- very important in the evolution of the early tetrapods
- vertebral column highly ossified
Vertebral types include:
- Lepospondylous (husk) vertebrae (found in many small Paleozoic types; centrum forms a single
structure, often spool-shaped and with hole for notochord)
- "Arch" vertebrae [found in labyrinthodonts and in all higher vertebrate classes; consists of two
sets of ossified arch structures (intercentra and pleurocentra)] including 1) Rhachitomous
vertebrae [most primitive type with wedge-shaped crescentic intercentra and paired
pleurocentra (small and between neural arches and intercentra); found in rhipidistians,
ichthyostegids and most "central" labyrinthodonts (some temnospondyls)],
2) Stereospondylous vertebrae [pleurocentra reduced or absent and intercentrum below the
neural arch and sometimes ring-shaped; found in many Late Permian and Triassic
temnospondyls] and 3) Anthracosaurs [pleurocentra increasing in size, fuse and become a
complete ring (=centrum of higher vertebrates); line which leads to reptiles have intercentra
reduced to small ventral wedges between the pleurocentra; second line (the embolomerous
condition) with each segment having two complete ring-shaped central structures]
Neural arches - well-developed and with zygapophyses giving added support to the vertebral
column; has transverse process for articulation with the ribs
Ribs - tetrapods with only one set of ribs; found from neck to anterior part of tail; reinforce the
body wall and protects the lungs and viscera; specialized rib (Sacral) connects pelvic girdle to
vertebral column
c. Skull
- primitive tetrapods with skull completely roofed by dermal bones
- tetrapods with longer snout and shorter skull table
- anterior and posterior parts of braincase becomes fuse
Major Bones of the Skull - bones down midline include elongate nasals and frontals; shortened
parietals and postparietals; premaxilla and maxilla well-developed and toothed
d. Sensory organs
PALEO LECTURE, PAGE 108
- The "Ear" - fish hyomandibular no longer needed to prop the jaws, becomes loosened; land
vertebrates need to pick up air vibrations (for "hearing"); hyomandibular laid just behind the
spiracle, becomes free to form a Stapes (probably first functioned to support braincase against the
cheek); later transmited vibrations from the Tympanum (the ear drum; primitively situated in an
otic notch at the rear of the skull roof) to the inner ear
- Lateral line system - fish hydraulic "sensory system" typically retained in water-living Paleozoic
amphibians but lost in higher vertebrate classes
- The Eyes - typically large in tetrapods and often in primitive types surrounded by sclerotic
plates
e. Limb Girdles
- Shoulder girdle - skull connection lost; humerus fits into laterally-placed concavity
- Pelvic girdle - much larger than plate seen in fishes and has joined to sacrum above; consists of
an ilium, ischium and pubis; femur fits into laterally-placed cavity
f. Limbs
- Pectoral limbs - humerus (proximal bone) articulates with the radius and ulna; radius and ulna
articulate distally with the carpus (wrist elements forming a hinge between the limbs and toes);
typically with four or five toes
- Pelvic limbs - proximal bone (femur) articulates with the tibia and fibula; tibia and fibula
articulates with the tarsus; tarsals articulate with the metatarsals (five toes)
g. Reproductive Systems
- probably initially with external fertilization and laid large numbers of small eggs in water; many
Paleozoic types with gill-bearing larval stage (referred to as "branchiosaurs")
3. Classification
Phylum Chordata
Subphylum Vertebrata (Craniata)
Infraphylum Gnathostomata
Superclass Tetrapoda
Unnamed Class
Family Ichthyostegidae
Class Amphibia (Batrachomorpha)
Order "Temnospondyli"
Family Trimerorhachidae
Suborder Capitosauria
Suborder Trematosauria
Infraclass Lissamphibia
Order Urodela
Order Anura
Class Unnamed
Superorder Lepospondyli
Order "Microsauria" (probably a polyphyletic group)
PALEO LECTURE, PAGE 109
Order Nectridea
Order Aistopoda
Superorder Reptiliomorpha
Order "Anthracosauria"
Order Seymouriamorpha
Order Diadectomorpha
4. Ichthyostegids
- earliest tetrapods but not ancestral to other groups; Upper Devonian (?) - Lower Mississippian
- some of the early tetrapods have as many as 8 toes (Ichthyostega had 7) that were developed
into paddle-like appendages; ichthyostegids were probably largely aquatic and could not fully
support their weight on land
5. "Temnospondyls"
- labyrinthodont amphibians that evolved from osteolepiform fishes; primitive features inherited
from these fish include labyrinthine infolding of dentine, palatal fanged teeth, vertebrae
composed of several centra elements
- derived features include formation of specialized anterior vertebrae for connecting to skull
(atlas-axis complex; not found in ichthyostegids), otic notch at back of skull (supported ear
drum?), primitive types often large (over 1 meter)
- Mississippian - Cretaceous; were the most important Carboniferous tetrapods
- often with large, flat heads; examples include the aquatic eryopoids and trimerorhacids; the
terrestrial, armored dissorophids and the metoposaurs (large-skulled aquatic amphibians)]
6. "Lissamphibians"
- may be a polyphyletic group; may have been derived from dissorophid temnospondyl
amphibians (or others say were derived from lepospondyls)
- includes frogs and toads (Salientia or Anura; Triassic-Recent), the long-bodied aquatic
salamanders (Urodela or Caudata; Jurassic-Recent) and the worm-like caecilians (Apoda or
Gymnophiona; Jurassic-Recent)
- with pedicellate teeth (base and crown of tooth separated by a zone of weakness of fibrous
tissue; probably related to tongue protrusion); teeth bicuspid; spool-shaped vertebrae; frogs and
salamanders with strange ear specialization by which an ear ossicle (the operculum) has a
muscular connection with the shoulder girdle (probably related to hearing and balance)
Frogs and Toads - greatly derived (most features related to jumping): only 5 to 9 trunk vertebrae;
posterior of sacrum fused (urostyle); no ribs; ilium rod-shaped and connects to last vertebrae;
long hind legs with tibia and fibula fused; radius and ulna fused; proximal tarsals elongate;
shoulder girdle firmly braced; skull forms "open" structure; external fertilization; tadpole stage
(herbivorous suspension feeders or algae eaters) known from Lower Cretaceous; adults
carnivorous; advanced types flip back of tongue out of mouth
-Triadobatrachus (Early Triassic, Madagascar) with frog-like skull but postcranium not very
frog-like; ancestral to modern frogs?
PALEO LECTURE, PAGE 110
7. Lepospondyls
- usually small, Mississippian to Permian-age amphibians; may have evolved from early
labyrinthodonts (but with no labyrinthine infolding, no palatal fangs and pits and no otic notch)
- characterized by lepospondylous vertebrae (spool-shaped bony cylinder surrounding the
notochord)
- includes the snake-like aistopods and lysorophids, the eel-like nectridians [Diplocaulus and
Diploceraspis with boomerang-heads], and the lizard-like terrestrial "microsaurs" (many believe
microsaurs are a polyphyletic group)
8. "Anthracosaurs" and their Kin
- Devonian to Permian; a paraphyletic group since they are ancestral to reptiles (often placed
within the Reptiliomorpha)
- Seymouriamorphs with combination of reptile and amphibian features; Amphibian features of
Seymouria include anthracosaur-like skull and gill-bearing larvae; Reptile-like features include
skull and cheek solidly attached; stapes (ear bone) reduced to a narrow rod; ilium expanded and
begin incorporating second sacral rib; vertebrae with swollen neural arches and large
pleurocentrum with tiny intercentrum
9. Diadectomorphs
- Pennsylvanian to Early Permian terrestrial "reptiliomorphs", very close to the origin of amniotes
- herbivorous with peg-like front teeth and grinding "molariform" teeth
XXV. A Myriad of Reptiles on Land
A. Characters of Reptiles:
1. Development of amniote egg - has a large yolk, a shell, and extraembryonic membranes
which protect the egg, supply nourishment and for gas exchange
Amniotes - probably a monophyletic group; probably originated in the Mississippian
2. loss of intertemporal bone; reduction in size of supratemporal, tabular and postparietal
3. loss of palatal "fangs" and labyrinthine infolding of tooth enamel
4. absence of otic notch
5. development of more efficient vertebral column (specialized anterior vertebrae = atlas/axis)
and reduce intercentra
6. specialized ankle joint developed [astragalus and fibulare (= calcaneum)]
7. wheat-shaped ventral scales; no ossified dorsal scales
B. Paleoecology of Early Reptiles
PALEO LECTURE, PAGE 111
- probably terrestrial since:
1. early reptiles usually found in terrestrial deposits
2. limbs, girdles and vertebral column are ossified and well-developed for terrestrial life
3. small body size, structure of teeth and probable arrangement of jaw musculature probably
indicate lizard-like habits for early amniotes (probably ate small terrestrial arthropods)
C. Reptile Classification and Radiation
- often based on patterns of openings of skull roof (temporal openings) behind the orbits
1. Anapsid condition - no temporal opening; Exs. = captorhinids, turtles
2. Synapsid condition - lower opening with postorbital and squamosal meeting above; Ex. =
mammal-like reptiles
3. Diapsid condition - two temporal openings present; Exs. = dinosaurs, pterosaurs and
ancestral condition of all modern reptiles except turtles
4. Euryapsid (Parapsid) condition - upper opening with postorbital and squamosal meeting
below; Exs. = plesiosaurs, ichthyosaurs
- derived from the diapsid condition through loss of the lower temporal fenestra
D. Classification of Primitive Reptiles (One of several available):
Series Amniota
Class Synapsida
Order Pelycosauria
Family Caseidae
Family Ophiacodontidae
Family Edaphosauridae
Family Sphenacodontidae
Order Therapsida
Family Dinocephalia
Family Dicynodontia
Family Cynodontia
Class Sauropsida
Subclass Anapsida
Family Procolophonidae
Family Pareisauridae
Family Mesosauridae
Family Captorhinidae
Order Testudines (Chelonia)
PALEO LECTURE, PAGE 112
Family Proganochelyidae
Suborder Pleurodira
Suborder Cryptodira
E. The Anapsids
- most primitive forms which are unquestionably reptilian; consists of "parareptiles" (milleretiids,
bolosaurs, procolophonids, pareisaurs) and the turtles
- typically small (0.3 to 0.9 meters long), lack temporal opening and otic notch; massive stapes
props braincase
1. "Protorothyeridae" (= Romeriidae, Millerettidae, etc.)
- a polyphyletic group of Pennsylvanian-Permian, small, lizard-like reptiles
2. Bolosauridae
- small, early herbivores
3. The Procolophonoids
- develop herbivorous feeding (jaws shorten, differentiation of the teeth, enlarge orbitotemporal
fenestra for large jaw muscles], late types with bony skull projections
4. The Pareiasaurs
- Middle to Upper Permian; up to three meters long; skull often with bony protruberances; leafshaped teeth (herbivores)
5. Captorhinids (Captorhinidae)
- with specialized dentition with multiple tooth rows
- probably more kin to diapsids than other early amniote groups
F. Synapsids
- have often been termed "mammal-like reptiles", but synapsids are now typically considered to
be a group distinct from "true reptiles"; the Synapsida often includes pelycosaurs, therapsids, and
true mammals
- synapsids were the earliest carnivorous amniotes (by Pennsylvanian constituted 50% of known
amniote genera; by Early Permian = 70%)
1. General Characteristics
- with a single lateral temporal opening (synapsid condition; primitive types with postorbital and
squamosal joining above; derived types with upper margin bounded by parietal)
2. Pelycosaurs
- Pennsylvanian-Permian
- probably derived from protorothyrid captorhinomorphs
- includes Ophiacodonts (carnivores); Sphenacodonts (highly predaceous forms such as
Dimetrodon; many with elongate neural spines forming "sails"), Edaphosaurs (herbivores;
usually with elongate neural spines with crossbars) and Caseids (herbivores)
PALEO LECTURE, PAGE 113
3. Therapsids
- Tetraceratops (Early Permian, Texas) may be the oldest therapsid (is intermediate in form
between the sphenacodont pelycosaurs and therapsids)
a. General Characteristics
- mandible with thin, extensive sheet of bone (the reflected lamina; for hearing); temporal
fenestra (opening) larger than pelycosaurs; single canine, jaw hinge anteriorly-placed and back of
skull is vertical; Skeleton with improved locomotion
- derived from advanced sphenacodonts
b. Classification of Therapsids
- include the Dinocephalians (very large Permian carnivores and herbivores); Anomodonts
(Permian to Triassic; herbivorous; most successful mammal-like reptiles; include the tusked
dicynodonts); Cynodonts (Permian to Jurassic; advanced mammal-like reptiles representing
transitional stages in the development of mammalian characteristics)
XXVI. Farewells to Land
A. Mesosaurs
- aquatic parareptiles of Permian age from Africa and South America; probably restricted to one
limited ocean basin and was used as evidence of continental drift
- up to one meter long, slender; with long, laterally-compressed tail and neck and paddle-like
feet; marginal teeth long and slender (for straining microplankton?)
B. Testudines (Chelonians)
- the turtles
- probably closely kin to pareisaurs and procolophonids
1. Structure
- shell composed of horny scutes covering bony plates; with carapace (dorsal portion of shell)
and plastron (ventral portion of shell)
- vertebrae [except cervicals (neck)] and ribs fused to shell; limbs and limb girdles modified for
sprawling posture
- anapsid skull; teeth rudimentary or absent
2. Classification
- divide into the Proganochelyds (primitive Triassic-age turtles), Pleurodires (side-necked
turtles), and Cryptodires (S-necked turtles; most successful turtle group)
C. Subclass (or Order) Ichthyopterygia (Ichthyosauria)
- Dolphin-, tuna- and shark-like neodiapsid reptiles of the Mesozoic
- body short, laterally compressed and fusiform
- skull highly modified for aquatic life (long beak; nostrils migrated far posteriorly; eyes greatly
PALEO LECTURE, PAGE 114
enlarged and surrounded by bony plates); with a euryapsid skull pattern
- vertebral centra amphicoelous (biconcave); tendency through time to develop a hypocercal tail;
limbs reduced to steering paddles
- reproduction probably took place in water and with live birth (some females with skeletons of
young ichthyosaurs inside them)
D. The Sauropterygians (Superorder Sauropterygia)
- lepidosauromorph neodiapsids that include the nothosaurs, pachypleurosaurs, plesiosaurs, and
possibly the placodonts; aquatic reptiles with euryapsid temporal opening
- Nothosaurs (limbs relatively normal; Triassic) and Plesiosaurs (develop paddles by adding toe
joints; Jurassic-Cretaceous) with nostils migrated far back on skull; ventral ribs form basket-like
structure; ventral portion of pelvic girdle expanded
E. Placodonts
- wierd Triassic, aquatic mollusc-eating neodiapsids (but with euryapsid temporal opening);
most with "pavement teeth"; kin to the "Sauroptergyia" and now often placed within that group
XXVII. Scale Bearers and Lizard Hipped Dinosaurs
A. Diapsids
- diapsids have two temporal openings separated by the postorbital and squamosal
- includes all modern reptile groups except turtles; also includes dinosaurs, pterosaurs,
plesiosaurs and several other ancient groups
1. Classification of the Diapsids (one of many available):
Series Amniota
Class Sauropsida
Subclass Diapsida
Infraclass Ichthyosauria
Infraclass Lepidosauromorpha
Superorder Sauropterygia
Order Placodonta
Order Nothosauroidea
Order Plesiosauria
Superorder Lepidosauria
Order Sphenodontida
Order Squamata
Suborder Lacertilia
Suborder Serpentes (Ophidia)
Infraclass Archosauromorpha
Family Trilophosauridae
Family Rhynchosauridae
Family Prolacertiformes
PALEO LECTURE, PAGE 115
Division Archosauria
Family Proterosuchidae
Family Erythrosuchidae
Family Euparkderiidae
Subdivision Crurotarsi
Family Phytosauridae (= Order Phytosauria)
Family Ornithosuchidae
Family Stagonolepididae (= Order Aetosauria)
Family Prestosuchidae
Family Poposauridae (= Order Rauisuchia)
Order Crocodylia
Subdivision Avemetatarsalia (See below)
Most important Groups Are:
B. Infraclass Lepidosauromorpha
- includes sphenodontids, lizards, snakes, and the extinct aquatic placodonts, nothosaurs, and
plesiosaurs
- differentiated from archosauromorphs by retention of sprawling posture; lateral undulation of
body during movement; early lepidosauromorphs with large sternum ("breast plate" for greater
flexion and stride)
- Order Sphenodontida (Family Sphenodontidae) - lizard-like, small reptiles from TriassicRecent
Order Squamata - includes Suborders Sauria, Amphisbaenia and Serpentes
- Sauria (lizards) with tendency towards streptostyly (with loss of lower temporal bar and loose
connection of posterior skull bones for greater biting force); teeth primitively subpleurodont or
pleurodont (attached to inside of jaw); may secondarily become acrodont (teeth fused to top of
jaw) or subthecodont (teeth in shallow pits); includes many taxa; Cretaceous marine lizards
include dolichosaurs, aigialosaurs and mosasaurs
- Serpentes (Ophidia) = snakes (Upper Cretaceous - Recent); temporal arches absent and upper
and lower jaws very loosely attached (for consuming large prey); vertebrae very numerous;
pectoral girdle and anterior limb absent (some snakes with vestiges of pelvic girdle and hind
limb); implantation of teeth subacrodont
C. Primitive Archosauromorphs (Infraclass Archosauromopha)
- most important structure uniting archosauromorphs is ankle (tarsus) and foot structure (related
to upright posture)
Most Important Groups are:
1. Family Trilophophosauridae
- small to medium-sized, Triassic-age, lizard-like "herbivorous" reptiles (teeth typically
tricuspid); postcranial skeleton like primitive archosaurs; Ex. = Trilophosaurus
PALEO LECTURE, PAGE 116
2. Family Rhynchosauridae
- heavily-built Triassic herbivorous lepidosaurians; advanced types with upper jaw with broad
crushing toothplates and parrot-like edentulous (toothless) beak
D. Division Archosauria
- the "ruling reptiles" including the dinosaurs, crocodiles, pterosaurs and many primitive groups
(the thecodonts)
1. Characteristics
- Skull with diapsid condition (two temporal openings); openings do not lose any of their arcades
("arches"); also with an antorbital opening (rarely more than one) between the orbit and the
snout; thecodont dentition (teeth placed in sockets)
- Postcranial skeleton with hind limb much better developed than the forelimb; tendency towards
bipedal pose involves change in hip and femur structure
2. Subdivision Crurotarsi
- with improved ankle joint (tarsus) that allows rotation between the astragalus and calcaneum
- tarsus may be used to divide Middle and Upper Triassic archosaurs into two groups; CrocodileNormal Pattern with process on the lateral surface of the astragalus fitting into a recess on the
medial surface of the calcaneum [found in crocodiles, phytosaurs, aetosaurs and rauisuchids);
Crocodile-Reverse Pattern with process on the calcaneum fitting into a recess in the astragalus
(found in lagosuchids, ornithosuchids and Euparkeria)
a. Family Poposauridae (= Rauisuchia)
- large, fierce Middle and Upper Triassic thecodonts (up to 6 meters)
b. Family Stagonolepididae (= Aetosauria)
- relatively large herbivorous quadrupeds of Late Triassic age; body with solid armor plate
c. Family Phytosauridae (= Phytosauria)
- very abundant, crocodile-like, Upper Triassic thecodonts
E. Crocodilians (Order Crocodilia)
- Crurotarsi that include the crocodiles, alligators and their relatives
1. Morphology
- Skull elongate, flattened, massive; evolutionary trend in posterior extension of the palatal bones
(premaxillae, maxillae, palatines and pterygoids) to form a secondary palate (for aquatic mode of
life or to support the elongate snout?); elaborate pneumatic ducts (for hearing airborne sounds?)
- Body elongate with long, flat tail; gastralia (ventral ribs) present; amphicoelous (biconcave) or
procoelous vertebrae (concavity in front, with convex posterior surface); dermal armor; with a
semi-improved gait [hind legs longer than front legs; pelvis triradiate; improved tarsal joint]
2. Classification
PALEO LECTURE, PAGE 117
- includes the Protosuchia and the Mesoeucrocodylia [largest assemblage of crocodiles; include
many Mesozoic marine types; posterior extension of palatine bones to form secondary palate;
Mesoeucrocodilia includes the Eusuchia (includes gavials, alligators and crocodiles; secondary
palate fully-developed)]
F. Dinosaurs
- Over 800 species of dinosaurs are known
1. Posture
- limbs brought under the body and moved in a fore-and-aft direction [femur inturned; pelvis
"socket" (acetabulum) open (perforate); improved tarsal joint (with formation of a “mesotarsal”);
digits form main surface that contacts ground (digitigrade posture)]
2. Ancestry
- probably derived from Ornithosuchians (close to Lagosuchus)
- dinosaurs became the dominant reptile group after the "end-Carnian Extinction Event" during
the Upper Triassic, which cleared ecospace for the dinosaurs to take over
3. Classification of Pterosaurs and Dinosaurs
- The following is one of several available:
Series Amniota
Class Sauropsida
Subclass Diapsida
Infraclass Archosauromorpha
Division Archosauria
Subdivision Avemetatarsalia
Infraorder Ornithodira
Order Pterosauria
Suborder Rhamphorhynchoidea
Suborder Pterodactyloidea
Superorder Dinosauria
Order Saurischia
Family Herrerasauridae
Suborder Theropoda
Infraorder Coelophysoidea - Family Coelophysidae (Procompsognathidae?)
Infraorder Ceratosauria - Families Ceratosauridae, Abelisauridae
Infraorder Tetanurae
Division Carnosauria
Subdivision Spinosauroidea - Families Megalosauridae, Spinosauridae
Subdivision Allosauroidea - Families Allosauridae,Carcharodontosauridae
Division Coelurosauria
Family Coeluridae
PALEO LECTURE, PAGE 118
Subdivision Maniraptoriformes
Families Tyrannosauridae, Ornithomimidae
Infradivision Maniraptora
Families Alvarezsauridae, Therizinosauridae
Cohort Deinonychosauria
Families Dromaeosauridae, Troodontidae
Suborder Sauropodomorpha
Families Plateosauridae, Massospondylidae
Infraorder Sauropoda
Families Vulcanodontidae, Euhelopodidae, Omeisauridae
Division Neosauropoda
Families Cetiosauridae, Diplodocoidea
Subdivision Macronaria
Family Camarasauridae
Infradivision Titanosauriformes
Families Brachiosauridae, Titanosauridae
Order Ornithischia
Families Pisanosauridae, Fabrosauridae
Suborder Thyreophora
Family Scelidosauridae
Infraorder Stegosauria
Infraorder Ankylosauria
Families Nodosauridae, Ankylosauridae
Suborder Cerapoda
Infraorder Pachycephalosauria
Infraorder Ceratopsia
Families Psittacosauridae, Protoceratopsidae, Ceratopsidae
Infraorder Ornithopoda
Families Heterodontosuridae, Hypsilophodontidae,Iguanodontidae,
Hadrosauridae
4. Saurischians
- with primitive pelvis structure with ilium at top, pubis pointing forward and ischium backward;
front limb shorter than hind; digits of manus (hand) and pes (foot) reduced; teeth occupied the
rims of the jaws; large openings reduced the weight of the skull
- saurischians dominated during the early Mesozoic but were outnumbered by the ornithischians
during the upper Mesozoic
- The most Important Saurischians are:
a. Theropods
- include all of the bipedal carnivorous dinosaurs
- neck is generally shorter than the trunk; the tibia is longer than the femur; hands bear sharp
claws and there are two or three fingers only; feet with three clawed toes (the fifth is always
reduced and the first or big toe is shortened and turned backwards); abdominal ribs present
PALEO LECTURE, PAGE 119
Range: Late Triassic-Cretaceous
- includes the coelophysoids (small, slender theropod dinosaurs), ceratosaurs (many with horns
and crests) and the tetanurans [with an opening in the maxilla (maxillary fenestra), and dorsal
vertebrae have cavities in their sides (pleurocoelous vertebrate) and the ascending process of the
astragalus covers a portion of the tibia; includes the Carnosaurs (spinosaurs and allosaurs) and
the Coelurosaurs (most important coelurosaur types are the Maniraptoriformes (reduction to three
long fingers; with a half Moon-shaped wrist bone) including ornithomimids ("ostrich
dinosaurs"), tyrannosaurids, and deinonychosaurs ("raptors")]
b. Sauropodomorphs
- typically heavily built quadrupedal dinosaurs with small heads and long necks; most with
peglike teeth; Upper Triassic- Upper Cretaceous
- "Prosauropods" - small- to large-sized; possible ancestors of sauropods; carnivorous,
herbivorous and perhaps omnivorous forms
- Sauropods were huge Jurassic/Cretaceous herbivores with quadrupedal pose, powerful limbs,
long tail, long neck and small head; jaws short and weak with small peglike or spoonshaped
teeth; front legs shorter than hind legs; metapodials (proximal foot bones) and phalanges (toes)
short, stout and spreading; include Cetiosaurids, Brachiosaurids, Camarasaurids , Titanosaurids
and Diplodocids
XXVIII. Bird-Hipped Dinosaurs
A. Characteristics of Ornithischians
- pubis points backward (bird-hipped); with single median bone at the tip of the lower jaw (the
predentary); jaw with beak, posterior to which is a grinding dention; most with concave cheek
region (therefore most with muscular cheeks); tendency for internal nostrils to be displaced
posteriorly
B. Classification of Ornithischians
1. Cerapoda
- with a gap between the teeth of the premaxilla and maxilla and with five or fewer premaxillary
teeth; with a thick layer of enamel on the inside of the teeth
- includes ornithopods, pachycephalosaurs and ceratopsians
a. Ornithopods
- had bird-like feet with blunt claws or hooves; include Fabrosaurids, Heterodontosaurids,
Hypsilophodontids, Iguanodontids (Cretaceous) and Hadrosaurids ("duck-billed" dinosaurs)
b. Pachycephalosaurs
- small group of Late Cretaceous "bone-headed" dinosaurs (with unusually thick skull roofs,
probably used for "butting contests" between males)
c. Ceratopsians
PALEO LECTURE, PAGE 120
- small to large dinosaurs with skulls ranging from relatively large to gigantic, often with horns
and large shields of bone; snout beaklike; almost exclusively quadrupedal; one of last evolved
(Cretaceous) and most abundant groups of dinosaurs
2. Thyreophorans
- with keeled scutes (bony armor) along the sides of their body
- include stegosaurs and ankylosaurs
a. Stegosaurs
- Mid Jurassic to Late Cretaceous armored quadrupedal ornithischians
- relatively large; with small skull, front legs short; back arched high over long hind limbs; with
series of plates and spines arranged in a row down the neck, trunk and tail
b. Ankylosaurs
- stocky dinosaurs with short, broad feet; with extensive development of bony, armored carapace,
often with tail club; Lower Jurassic-Upper Cretaceous
C. Biology and Extinction of Dinosaurs
1. Were Dinosaurs Warm-Blooded?
- Evidence cited that dinosaurs were endotherms includes the following:
a. Erect posture - limbs held vertically (with metabolism like birds and mammals)
b. Bone structure - dinosaurs have haversian canal systems in their bones like those of
mammals (indicates more rapid metabolic processes; but these seem to be present in large
animals in general and are absent in small animals)
- but dinosaurs did not have determinant growth and continued to increase in size throughout life
(unlike birds and mammals)
c. Population Studies/ Community Structure - carnivorous dinosaur numbers (versus
herbivores) are more like that of mammals than reptiles
d. Long-necked dinosaurs would have to have a more efficient heart in order to pump blood up
to their brains
e. A few dinosaurs were at least as intelligent as birds
f. Dinosaurs show social behavior (such as herding and "nurseries") that is unknown among
other reptiles
g. Dinosaurs have been discovered in Mesozoic "polar regions"
h. Some dinosaur fossils have feathers
PALEO LECTURE, PAGE 121
i. Growth Rates - reptiles grow slowly, dinosaurs grew quickly like birds and mammals
j. Oxygen Isotopes - ratios are influenced by temperature; indicates more similarity to modern
endotherms than ectotherms
However, dinosaurs would probably maintain a relatively constant internal temperature due to
their small surface area versus volume (Homeotherms or Gigantotherms). Also, if dinosaurs were
such great endotherms why all of the plates, frills, spikes and nasal cavities that probably served
as heat exchangers, helping to warm and cool their bodies?
2. Extinction of the Dinosaurs
- dinosaurs originated in the Middle Triassic and became extinct at the end of the Cretaceous
(Cretaceous/Tertiary, K/T, or Maastrichtian/Danian Boundary; approximately 65 Ma) [some say
a few survived into the early Cenozoic]
a. Catastrophic Dinosaur Extinction
a1. Extraterrestrial Causes - large asteroid (10 to 20 kilometers across) hit the earth, creating a
cloud of dust and something similar to "nuclear winter"; decrease in photosynthesis, increase in
carbon dioxide, increase in acidity of oceans and a short-term "greenhouse effect"?
- evidence includes the iridium layer at the Cretaceous/Tertiary boundary found at about 50
localities throughout the World (probably deposited over a period no more than a few thousand
years), the presence of glassy spherules (tektites) and "tsunami beds" at the K/T boundary
a2. Vulcanology models - geochemical data in boundary rocks indicate major volcanic
eruptions (e.g., The Deccan Traps of India) at the end of the Cretaceous
- would produce greenhouse gases that would trigger rapid climate change
b. Hypothesis of Gradual Change
- end of Cretaceous marked by major regression and drying up of epicontinental seas
- tectonic activity, mountain building led to major change in climate and seasonality
- Western North America may have seen gradual decrease in temperature between late
Cretaceous and Paleocene of 10°C ; evidence includes gradual extinction and replacement of
dinosaurs and other groups (including plesiosaurs, pterosaurs, ostracods, bryozoans, ammonites
and bivalves, all with low diversity at the end of the Cretaceous)
XXIX. Flying and Gliding Reptiles
Pterosaurs - active flying reptiles from the Upper Triassic through Upper Cretaceous; most from
shallow marine environments; most genera short-lived and from small geographic areas
A. Classification
PALEO LECTURE, PAGE 122
Series Amniota
Class Sauropsida
Subclass Diapsida
Infraclass Archosauromorpha
Division Archosauria
Subdivision Avemetatarsalia
Order Pterosauria
Suborder Rhamphorhynchoidea
Suborder Pterodactyloidea
B. Morphology
1. Skull
- typically large; bones tend to fuse in skull; large brains; large orbits; quadrate slanted anteriorly
and streptostylic, for increased jaw mobility; nostrils migrated posteriorly; with long beak and
long, sharp teeth
2. Postcranial skeleton
- neck elongate; trunk very short with long sacral region; rhamphorynchoids with long tail
- Active Flight indicated by: hollow bones and with bird-like pneumatic foramina (for
respiration; with high metabolic rate?); keeled sternum; pterodactyloids with well-developed
shoulder girdle [scapula (shoulder blade) articulated with fused anterior trunk vertebrae
(notarium)]; humerus forms pulley-like structure (for attachment of large flight muscles); carpal
("wrist") bone modified to form splint-like pteroid (serves as anchor for a narrow membrane that
extends to the base of the neck); first three fingers short, fourth finger greatly elongate to support
the wing membrane (attached to posterior portion of trunk), fifth finger absent
- rhamphorynchoids had long tails; pterodactyloids had short tails
XXX. Birds, Inventors of the Feather
Class Aves (Birds) - very difficult vertebrate fossils to work with; generally poor preservation
and conservative morphology (beneath the feathers)
- most diversification in the Cenozoic but most modern families present by end of Eocene
- taxonomic interrelationships are debated, even among many modern groups
A. Characteristics
- highest metabolic rate of any vertebrate
- many modifications in connection with habits, social organization and flight
1. Skeleton
- bones are pneumatic (with extensive air-sac system for respiration)
- compact skeleton with wing and leg bones are reduced in number and many elements fused
[including hand, foot, sacral vertebrae (fused to form a synsacrum), tail vertebrae (fused to form
a pygostyle)]
PALEO LECTURE, PAGE 123
- ribs with uncinate processes (small bony struts that bind the rib cage together)
- clavicles fused to form the furcula (the "wishbone"); stabilizes the shoulder joint and prevents
collapse of the shoulder during flight
- sternum ("breast bone") with large keel (carina) that provides a broad base for the flight
muscles
- typical avian foot with three toes in front and one behind (anisodactyly); some unrelated groups
with two toes in front and two behind (the yoke-toed or zygodactyl condition; includes
woodpeckers, cuckoos and parrots)
2. Skull
- with large orbits (incompletely surrounded by bone), in front of which is an antorbital opening;
single temporal opening (but derived from the diapsid condition)
- large braincase; skull bones typically fused and sutures obliterated
- modern birds toothless with beak covered with a horny bill
B. Origin of flight
- theories can be divided into two groups, the "arboreal" theories and "cursorial" theories
1. Arboreal theory-has been proposed by most workers; four-footed, ground-dwelling reptile
became bipedal, then climbing, then began leaping from tree to tree. Later it began parachuting,
gliding and finally included active, powered flight
2. Cursorial theory - feathers developed as thermoregulatory devices for insulation; then used
for trapping insects; then provided lift during running and leaping; then flight
C. Classification of Birds (One of many available):
Class Aves
Family Archaeopterygidae
Subclass Pygostylia
Family Confuciusornithidae
Order Oviraptosauria
Infraclass Ornithothoraces
Order Enantiornithes
Supercohort Ornithomorpha
Cohort Ornithurae
Order Hesperornithiformes
Subcohort Carinatae
Order Ichthyornithiformes
Superdivision Neornithes
Division Palaeognathae
Orders Lithornithiformes, Ratites
PALEO LECTURE, PAGE 124
Division Neognathae
Subdivision Galloanserae
Orders Anseriformes, Galliformes
Subdivision Neoaves
Superorder unnamed ['waterbird assemblage']
Infraorder unnamed
Orders Gruiformes, Ralliformes
Infraorder unnamed
Orders Pelecaniformes, Ciconiiformes
Infraorder Unnamed
Orders Charadriiformes, Phoenicopteriformes, Podicepidiformes,
Falconiformes, Procellariformes, Gaviiformes, Sphenisciformes
Order Strigiformes
Superorder unnamed
Orders Apodiformes, Caprimulgiformes
Order Musophagiformes, Columbiiformes, Psitaciformes,
Cuculiformes
Superorder unnamed ['derived land birds']
Orders Piciformes, Coliiformes, Trogoniformes, Bucerotiformes,
Coraciformes, Passeriformes
There are many groups of birds. I am only going to cover those of paleontologic interest:
1. Archaeopterygids
- includes Archaeopteryx, the earliest known bird (pigeon-size); Jurassic
- no unique features in the bony skeleton to differentiate them from dinosaurs (dinosaur fossils
from China indicate at least some dinosaurs had feathers)
- Skull birdlike with an expanded braincase and large eyes; sutures mostly closed; but
Archaeopteryx had thecodont teeth
- Skeleton with vertebral column primitive with amphicoelous (biconcave) vertebrae; tail
dinosaur-like with two lateral rows of feathers; hind legs and pelvis similar to saurischian
dinosaurs; clavicles joined to form a bird-like furcula but no keeled sternum
2. Toothed Birds and Divers
- includes Hesperornithiformes (loon-like, flightless, toothed Cretaceous birds), Grebes
(Podicipediformes), loons (Gaviiformes), penguins (Sphenisciformes; wing bones form a swim
fin), pelicans (Pelecaniformes; 2 meter-long plotopterids were largest swimming birds),
albatrosses/shearwaters (Procellariiformes) and Ichthyornithiformes (tern-like toothed Cretaceous
birds)
3. Water Birds
- include Orders Charadriiformes (shorebirds, including plovers, snipes, gulls, terns, auks, and
sandpipers), Anseriformes (ducks, geese and swans) and Ciconiiformes (wading birds such as
storks, herons, bitterns, ibises, spoonbills)
- Charadriiforms may be ancestral to all other large water birds except the Ciconiiformes; most
PALEO LECTURE, PAGE 125
Late Cretaceous fossil birds that are not hesperornithiforms belong to the ancient shorebirds
(example= Telmatornis)
4. Flightless Birds
- If there is no continual selection for the maintenance of flight apparatus birds tend to become
flightless
- major changes include loss of the flight muscles; reduction in the wing and bones of the
pectoral girdle; loss of the keeled sternum; obtuse angle of the scapulo-coracoid articulation; with
broad unossified region between the ilium and ischium (the ilioischiatic fenestra); some ratites
with skull sutures apparent; tendency to become large (note that most of these are neotenic
features - i.e. they retain the "youthful" condition)
- "Ratites" include gigantic flightless birds supposedly differentiated by their palaeognathous
palate; is probably a polyphyletic group that includes moas (New Zealand; some over three
meters tall), elephantbirds (up to 500 kilograms), ostriches, rheas, cassowaries, emus, tinomous
and kiwis
- Neoavian bird groups that developed flightless members include the orders Gruiformes (cranes,
rails, and the giant Early Tertiary carnivorous phorusrhacids), Diatrymiformes (over two metertall, probably carnivorous, flightless birds from the Early Tertiary)
5. Birds of Prey - include the hawks and owls
a. Falconiformes - includes falcons, hawks, eagles, vultures, ospreys and secretarybirds; with
raptorial adaptations (sharply hooked beak; powerful feet with long claws and an opposable toe;
strong fliers)
b. Owls (Strigiformes) - nocturnal birds of prey; features such as the short-hooked beak and
powerful talons are convergent with the falconiforms; Paleocene-Recent
6. Land Birds
- very difficult to figure out phylogenies; are beginning to be worked out by using diagnostic
bones such as the stapes
- most important group are the Passerines (Order Passeriformes); songbirds; with over 5000
modern species (three-fifths of all living birds); placed in from 50 to 70 families of Suboscines
and Oscines; with perching foot consisting of a very large first toe directed straight back and
opposed to the other three; differentiated by morphology of the palatal bones (the
aegithognathous condition), by the sperm structure, by the voice box and stapes structure
XXXI. Hairy Reptiles with Complex Ears: the Early Mammals
A. Classification of Mammals - this is one of several available:
Class Mammalia
Family Sinocondontidae
Subclass Mammaliaformes
PALEO LECTURE, PAGE 126
Family Morganucodontidae
Infraclass Holotheria
Family Kuehneotheriidae
Order Docodonta
Superdivision Australosphenida
Division Monotremata
Superdivision Theriimorpha
Order Triconodonta
Division Theriiformes
Order Multituberculata
Superlegion Trechnotheria
Order Symmetrodonta
Legion Cladotheria
Superfamily Dryolestoidea
Sublegion Boreosphenida
Order Deltathroida
Infralegion Theria
Cohort Marsupialia
Magnorder Ameridelphia
Order Didelphimorphia
Family Didelphidae
Order Paucituberculata
Families Caenolestidae, Argyrolagidae,
Caroloameghinidae
Order Sparassodonta
Families Borhyaenidae, Thylacosmilidae
Magnorder Australidelphia
Order Microbiotheria
Order Dasyuromorphia
Order Peramelemorphia
Order Notoryctemorphia
Order Diprotodontia
Cohort Placentalia (Eutheria)
Magnorder Afrotheria
Order Tubulidentata
Order Afrosoricida - Families Tenrecidae, Chrysochloridae
Order Macroscelidea
Grandorder Paenugulata
Order Hyracoidea
Mirorder Tethytheria
Order Sirenia
Order Proboscidea
Families Moeritheriidae, Deinotheriidae
Suborder Elephantiformes - Families Mammutidae,
PALEO LECTURE, PAGE 127
Gomphotheriidae, Stegodontidae, Elephantidae
Magnorder Xenarthra
Order Loricata (Cingulata) - Families Dasypodidae,
Glyptodontidae
Order Pilosa - Families Myrmecophagidae, Bradypodidae,
Megalonychidae, Megatheriidae, Mylodontidae
Magnorder Boreoeutheria
Order Leptictida
Order Anagalida
Order Apatemyida
Order Taeniodonta
Order Tillodontia
Order Pantodonta
Order Pantolesta
Order Dinocerata
Grandorder Laurasiatheria
Order Lipotyphla - Suborders Erinaceomorpha,
Soricomorpha
Order Chiroptera - Orders Megachiroptera, Microchiroptera
Mirorder Ferungulata
Superorder Cetartiodactyla
Order Arctocyonia
Order Mesonychidae
Order Artiodactyla
Family Dichobunidae
Suborder Suiformes (Bunodontia) - Families
Entelodontidae, Suidae, Anthracotheriidae,
Hippopotamidae
Suborder Selenodontia
Infraorder Tylopoda - Families
Merycoidodontidae, Camelidae
Infraorder Ruminantia – Families
Hypertragulidae,Tragulidae, Antilocapridae,
Giraffidae, Cervidae, Mochidae, Bovidae
Order Cetacea - Suborders Archaeoceti, Odontoceti,
Mysticeti
Order Perissodactyla
Suborder Hippomorpha - Families Equidae,
Brontotheriidae
Suborder Ancylopoda - Family Chalicotheriidae
Suborder Ceratomorpha – Superfamilies
Tapiroidea, Rhinoceratoidea
?Superorder Bulbulodentata - Family Hyopsodontidae
Superorder Meridiungulata - Families Litopterna,
Notoungulata, ?Astrapotheria, ?Pyrotheria
PALEO LECTURE, PAGE 128
Superorder Unnamed
Order Creodonta
Order Carnivora
Family Miacidae
Suborder Feliformia
Family Nimravidae
Infraorder Aeluroidea - Families Viverridae,
Herpestidae, Hyaenidae, Felidae
Suborder Caniformia
Families Canidae, Ursidae,
Amphicyonidae, Mustelidae, Procyonidae
Infraorder Pinnipedia - Families
Enalilarctidae, Otariidae,
Odobenidae, Desmatophocidae,
Phocidae
Order Pholidota
Grandorder Euarchontoglires
Superorder Archonta
Suborder Plesiadapiformes
Order Primates
Suborder Strepsirrhini
Infraorder Adapiformes
Infraorder Lemuriformes - Families Lemuridae,
Indriidae,Daubentoniidae, Lorisidae,
Galagidae
Suborder Haplorhini - Families Omomyidae,
Tarsiidae
Suborder Anthropoidea
Infraorder Platyrrhini - Families Cebidae, Atelidae
Infraorder Catarrhini
Families Oligopithecidae, Parapithecidae,
Propliopithecidae
Superfamily Cercopithecoidea - Family
Cercopithecidae
Superfamily Hominoidea - Families
Proconsulidae, Hylobatidae, Hominidae
Order Scandentia
Order Dermoptera - Families Paromomyidae,
Galeopithecidae
Superorder Glires
Family Zalambdalestidae
Order Rodentia
Suborder Sciurognathi
Superfamily Ischyromyoidea
Infraorder Sciuromorpha
PALEO LECTURE, PAGE 129
Infraorder Myomorpha
Suborder Hystricognathi
Infraorders Hystricomorpha, Phiomorpha,
Caviomorpha
Order Lagomorpha
B. Characteristics of Mammals
1. Soft Anatomy
- have hair and specialized mammary glands for suckling their young
- platypus and echidnas in egg-laying Ornithodelphia (Prototheria); marsupials (Metatheria) have
a marsupium (a pouch in which most embryonic development takes place); placentals (Eutheria)
have development taking place in the uterus and the embryo is nourished by the placenta (the
tissues shed following a birth)
- mammals are intelligent with complex behavioral patterns
- mammals are endothermic and usually have high metabolic rates
2. Osteological features
a. Skeleton
- determinate growth (grow rapidly but achieve definitive body size); once grown epiphyses on
long bones fuse with the shaft; cynodonts and early mammals with atlas/axis vertebrae forming
ring in living mammals for rotation of head on vertebrae); mammals with dorsoventral flexion
between double occipital condyle (posteroventral "knobs" on skull) and atlas; trunk vertebrae and
ribs in therapsids to early mammals restrict lateral flexion and enable trunk to be flexed in a
sagittal plane; appendicular skeleton modified for upright posture
b. Skull features
- usual definition of a mammal osteologically is presence of a dentary condyle on the jaw
articulating with a glenoid in the squamosal; incisors, canines and premolars replaced only once;
molars not replaced, with two roots and specific pattern of occlusion; with single bony nasal
opening in the skull
Middle Ear Origins - reptiles and birds with single ear ossicle (stapes); mammal ear with chain of
three bones (malleus, incus and stapes) which conduct vibrations from the typanum to the inner
ear; formation of dentary-squamosal articulation frees articular (mandible bone) to become the
malleus and the quadrate (skull bone) becomes the incus
c. Teeth
- very important in mammalian paleontology
- mammals are diphyodont (with two tooth generations; deciduous and permanent)
- molars have two or more roots and complex crown morphology
- living monotremes lack functional teeth; other mammals with four classes of teeth in each jaw;
anterior teeth (incisors) simple in form; canine single, large and conical and is anterior-most
tooth of the maxilla; teeth immediately behind upper and lower canines are premolars [usually
PALEO LECTURE, PAGE 130
become increasingly molariform in structure posteriorly; incisors, canines and premolars usually
with deciduous precursors shed early in life]; molars with no deciduous precursors and do not
erupt until animal begins to reach its definitive body size
- upper molars usually with square crowns with three roots and lower molars with narrower
rectangular crowns and two roots
- numbers of teeth in each class (incisors, canines, premolars and molars) summarized in a dental
formula (common opposum Didelphis with formula I5/4, C1/1, P3/3, M4/4 and generalized
placentals with dental formula I3/3, C1/1, P4/4 and M3/3)
- marsupials and placentals derived from Cretaceous therian mammals with tritubercular or
tribosphenic cheek teeth (both upper and lower molars with three prominent tubercles or cusps)
- upper molars with cusps forming a trigon; consists of a medial protocone, anterior paracone,
and posterior metacone
- lower molars with cusps forming a trigonid; consists of a lateral protoconid, anterior paraconid
and posterior metaconid
- fourth cusp, if present, is almost always directly behind the protocone or protoconid and is
called the hypocone (upper) or hypoconid (lower molar)
- fifth cusp, the entoconid, is often present on lower molars; the entoconid and hypoconid enclose
a heel (= talonid) posterior to the trigonid
- trigons and hypocones on successive upper molars form a series of triangles formed by the
trigonid, hypoconid and entoconid on lower molars; upper and lower cheek teeth occlude in
different ways and can be determined through studies of cusps patterns and wear facets
- molars with cusps (points for puncturing), crests (lines for shearing) and broad-basined areas
(planar areas for crushing or grinding)
C. Primitive Mesozoic Mammals and Monotremes
- nearly all early mammals were very small (probably up to 10 cm and 20-30 grams)
1. Monotremes (Early Cretaceous? - Recent)
- have milk glands, hair and one lower jaw element but lay eggs and have many reptilian
characteristics in their skeletons and soft anatomy
- includes the duckbill platypus and spiny anteaters or echidnas
2. Triconodonts
- Late Triassic to Late Cretaceous
- basic dental structure with tricuspid alignment on the molars
- includes the morganucondontids, amphilestids and triconodontids
3. Symmetrodonts
- shrew-sized mammals known from jaw fragments and dentition; Upper Triassic - Upper
Cretaceous
- mandible slender and long; lower molars triangular with asymmetrical cusp arrangement
- divided into the kuehneotheriids, Amphidontids and Spalacotheriids
4. Docodonts
- Middle to Late Jurassic; were probably size of small mouse and with elongate snouts
PALEO LECTURE, PAGE 131
- has articular-quadrate articulation but primary hinge is the dentary-squamosal
- developed advanced "square-cusped" molar patterns
5. Multituberculates
- most diverse and numerous Mesozoic mammals
- rodent-like; Late Jurassic-Early Oligocene; replaced the rodent-like therapsids (tritylodonts) in
the mid-Jurassic and were later replaced in the Paleocene (by competition with condylarths,
primates and rodents?)
- skull low and broad with eyes facing laterally; with pair of enlarged procumbent lower incisors;
with low many-cusped molariform teeth
6. "Therians of Metatherian-Eutherian Grade"
- a wastebasket category to include therians with tribosphenic dentition but not sufficiently
known to place with the marsupial or placental groups
- includes poorly known Cretaceous therians such as the "Trinity Therians" (Kermackia,
Pappotherium and Holoclemensia from the Paluxy/Antlers Formation of Texas)
- the oldest undisputed eutherian is a well-preserved shrew-sized placental from the Early
Cretaceous of Mongolia, which proves that there were true placental mammals by this time
D. Marsupials
- young born in a very immature (altricial) developmental state and undergo subsequent growth
attached to the teats of the female (usually in an abdominal pouch)
- now occur only in North America, South America and Australia; fossils from Early-Middle
Cenozoic of Europe, early Cenozoic of north Africa and early Cenozoic from Antarctica
1. Marsupial (Metatheria) versus Placental (Eutheria) Characteristics
MARSUPIALS
PLACENTALS
1.Postorbital bar usually lacking
1.postorbital bar present
2.Braincase relatively small
2.braincase relatively large
3.Posterior palatal vacuities usually present 3.posterior palatal vacuities rare
4.a poorly developed auditory bulla
4.auditory bulla commonly well developed and of
various origins derived from alisphenoid
5.Angle of jaw usually inflected medially
5.lower jaw usually not inflected
6.Dental formula derived from
I5/4 C1/1 P3/3 M4/4
6.Dental formula derived from I3/3 C1/1 P4/4 M3/3
(6 premolars in primitive species)
7.essentially monophyodont teeth; only
third premolar is replaced
7.diphyodont teeth; replacement of most antemolar
teeth
PALEO LECTURE, PAGE 132
8.relatively broad stylar shelf on upper
molars in most polyprotodont forms
8.relatively narrow stylar shelf in most forms
9. hypoconulid and entoconid are twinned
and separated from the hypoconid
9. no twinning
10.Epipubic bone; both sexes of most forms 10.no epipubic bones
11.None possess baculum or os clitoridis
11.baculum or os clitoridis common
12.presumed to have retained the original
therian reproductive mode
12.with derived, placental mode of reproduction
13.with altricial young
13.precocious young common
13.retain somewhat lower metabolic rate
rate
14.typically develop an elevated basic metabolic
2. Interrelationships of the Metatheria
- classifications have largely been based on incisor morphology and modification of bones in the
hind foot
a. Incisor morphology
- Polyprotodont - typically many incisors (up to 5 above and 4 below); incisors approximately
equal size; includes all known North American and living South American taxa
- Diprotodont - upper incisors commonly reduced to 3 pairs or less and lower incisors consist of
one pair of procumbent teeth; one of each incisor is enlarged relative to others; canines lacking
and with long diastema separating incisors from cheek dentition; cheek dentition strongly
bilophodont; includes most, but not all, Australian forms
b. Foot modifications
- Syndactyly - modification of bones of hind foot found in many Australian forms; digits II and
III of hind foot reduced and incorporated in a single dermal sheath (probably for grooming)
- Didactyly- no foot modification
2. Classification of the Metatheria
This is a classification scheme that was modified from Woodburne (1984) for the Marsupials (I
have only included the most common taxa):
Infraclass Metatheria
a. Cohort Ameridelphia
PALEO LECTURE, PAGE 133
- includes American Marsupials
a1. Order Didelphimorphia
- polyprotodont and didactylous; Late Cretaceous - Recent; includes the Families Didelphidae
(most primitive marsupials and probably ancestral to other types; includes the American
oppossum), Necrolestidae (mole-like), Argyrolagidae (kangaroo rat-like)
a2. Order Paucituberculata
- pseudodiprotodont and didactyl; Early Eocene to Recent of South America and Lower Eocene
of Antarctica; includes several groups of rodent-like marsupials
a3. Order Sparassodonta
- includes the Borhyaenidae (very successful group of medium to large-sized dog-like marsupials
from the Late Paleocene - Pliocene of South America) and the Thylacosmilidae (late MiocenePliocene of South America; "sabre-toothed" marsupials)
b. Cohort Australidelphia
- includes Australian Marsupials
b1. Order Dasyurida/Dasyuromorpha
- includes superfamilies Dasyuroidea [small-to-medium sized didelphid-like insectivores,
carnivores and omnivores; dental formula 4/3 1/1 2-3/2-3 4/4; includes Families Dasyuridae
(shrew- to wolf-sized carnivorous marsupials; "native cats", Tasmanian devil), Myrmecobiidae
(numbats) and Thylacinidae ("pouched wolf")
b2. Order Notoryctemorphia
- includes the Superfamily Notoryctoidea (Family Notoryctidae; "marsupial moles")
b3. Order Peramelemorphia
- polyprotodont and syndactyl; includes the Superfamily Perameloidea - rectangular tooth crowns
[including Families Peramelidae and Thylacomyidae (bandicoots, rabbit-like)]
b4. Order Diprotodonta
- diprotodont and syndactyl
This order includes the following taxa:
Suborder Vombatiformes
Superfamily Vombatoidea [includes Families Thylacoleonidae ("marsupial lions"; MiocenePleistocene), Vombatidae (wombats; burrowers), Palorchestidae (Miocene-Pleistocene;
often ground sloth-like), Diprotodontidae [sheep- to hippopotamus-sized quadrupedal
marsupials from Australia (Miocene- recently extinct) and New Guinea (PliocenePleistocene)] and Wynyardiidae
Superfamily Phascolarctoidea [includes Family Phascolarctidae (koalas)]
PALEO LECTURE, PAGE 134
Suborder Phalangeriformes/Phalangerida
Superfamily Phalangeroidea - may be most primitive diprotodonts; includes Families
Macropodidae ["rat-kangaroos", wallabies and true kangaroos from Australia (MioceneRecent) and New Guinea (Pliocene-Recent); dental formula 3/3 0-1/0 2/2 4/4]
- True kangaroos (macropodines) typically lophodont (loop-like enamel pattern on teeth) and
with high-crowned teeth; most with only one or two molars functional at any one time; most
are medium- to large-size with bipedal leaping gait (tibia greatly elongate, metatarsus
elongate; loss of toes; long, strong tail)
E. Primitive Eutherian Mammals
- classification difficult due to incomplete fossil record and very similar dentitions; classification
may be assisted by morphology of the auditory bulla (bones surrounding the ear region)
"Insectivores" ("Order Insectivora" of older classifications)
- tremendous problems in classification; postcranial skeleton primitive [pentadactyl (five-toed)
limbs and typically plantigrade locomotion]; typically small, lack an ossified auditory bulla,
relatively-complete dentition with sharp-cusped teeth and canines often reduced
- with approximately 60 modern and 150 fossil genera
- includes the Liptotyphlans (hedgehogs with square molars due to development of hypocone;
shrews often with pigmented teeth and with paracones and metacones forming a W-shaped outer
wall on the upper molars; moles with powerful forelimbs for digging and paracones and
metacones form a W-shape)
- true insectivores (Liptotyphla) are a sister group to the bats
XXXII. The World Blossoms
Division Anthophyta (Angiospermophyta, Angiospermophytina, Angiospermae) - flowering
plants (Cretaceous- Recent); include the majority of recent plants
A. Characteristics of Angiosperms
- with pollen-producing flowers (flowers = modified leaves); pollen wind-carried or insect-borne;
pollen lands on stigma (end portion of female element); pollen tube grows to the ovules for the
transport of sperm; one portion of the sperm fertilizes the egg and another portion unites with a
second portion of the ovule (which generally forms a structure which provides nutrients for the
growing embryo) = "double fertilization"; seed that develops is totally encased inside a fruit
- angiosperms are very successful because the diploid sporophyte dominates the life cycle (as in
other seed plants); the sporophyte of land-dwelling types has root and shoot systems, as well as
other features to allow it to take up and conserve water and dissolved minerals; the sporophyte
retains and nourishes the gametophyte and the embryos are nourished by a unique tissue (the
endosperm) within the seed; the seed are packaged in fruits, which also help to protect and
disperse them; evolution of flower greatly led to the diversity of the angiosperms
B. Classification of Angiosperms
PALEO LECTURE, PAGE 135
1. Class Monocotyledonae/Liliopsida
- include grasses, lilies, sedges, palms, pineapples and orchids; ?Triassic, Cretaceous-Recent
- usually with floral parts in groups of three (e.g., three stamens - the pollen-bearing portions of
the flowers); leaves usually parallel veined; usually with only one cotyledon (the "seed leaf" of
the embryo); stems are usually herbaceous and rarely have secondary growth
2. Class Dicotyledonae/Magnoliopsida
- include herbs and woody plants, cacti, and water lilies; ?Jurassic, Cretaceous-Recent
- floral parts occur in groups of four or five; vascular bundles are arranged in a circle around the
pith of the stem; often with secondary growth (thickens the vascular bundles and makes them
stronger); usually leaves are net veined and their embryos have two cotyledons ("seed leaves")
- the dicots are probably paraphyletic; most "dicots" have tricolpate pollen (these are termed
"eudicots" or "tricolpates"; other dicots and the monocotyledons have monosulcate pollen (it
therefore appears that the monocots were derived from monosulcate "dicots")
C. Tertiary Climate and Vegetation (North American Model)
1. Broad-leaved evergreen "gymnosperms" became extinct at the Cretaceous/Tertiary boundary,
to be replaced by deciduous dicots
2. Paleocene to Early Eocene global climate became warmer and precipitation increased, with
expansion of tropical forests to about 50° to 60° North latitude
3. Upper Eocene with decline in temperature and drier climates, and with spread of broadleaf
deciduous forests
4. During Miocene with drier climates and development of widespread grasslands (grasses have
continuously-growing leaves and can withstand heavy grazing), and with adaptive radiation of
"weeds" (the Compositae, mostly annual or perennial herbs capable of rapid development and
colonizing disturbed habitats)
XXXIII. The Great Placental Radiation
A. Bats (Order Chiroptera)
- only order of mammals specialized for true flight
- in number of species are the second largest order of mammals
- may have descended from soricomorph insectivores and are the sister group to the "true
insectivores" (liptotyphlans)
1. Structure
Postcranial - wings supported by four fingers; thumb is freed and clawed; legs and pelvis
developed for "hanging around"
Skull - orbit usually open behind; auditory region greatly enlarged; dentition varied; often with
tribosphenic molars (upper molars triangular) or squared with a W-shaped ectoloph, a large
protocone and smaller hypocone)
PALEO LECTURE, PAGE 136
2. Classification
a. Megachiropterans or Megabats (Suborder Megachiroptera)
- include the fruit-eating bats or "flying foxes" of the Old World tropics; Oligocene - Recent;
well-developed eyes, large olfactory lobes (good sense of smell; usually do not echolocate);
molars often specialized
b. Microchiropterans or Microbats (Suborder Microchiroptera)
- include most species of bats; almost worldwide in distribution; Lower Eocene - Recent; small,
nocturnal (active at night) and usually with small eyes; most are echolocators; considerable
diversity in diet; upper molars with w-shaped shearing cusps
B. Plesiadapiforms
- previously placed within the Primates (and still considered to represent a sister group to them)
- late Cretaceous - Eocene; Plesiadapids had a rodent-like dentition with a long diastema ("gap")
between the procumbent incisors and grinding molar teeth (probably herbivorous diet)
C. Primates (Order Primates)
- possible that primates and rodents share a common ancestor in the late Cretaceous
- usually scansorial ("scurrying"), small- to medium-sized forest-dwelling herbivores or
omnivores
1. General Characteristics
- Skeleton - retain a primitive, generalized skeleton, with five fingers and toes on the hands and
feet; trend toward increasing the mobility of the thumb and big toe; orthograde (upright) posture;
typically cling or sit vertically when resting; locomotion generally quadrupedal
- Skull - facial part of skull is reduced in more advanced primates; nasal apparatus generally
reduced; eyes face forward on skull; brain relatively large; often with broadly-basined upper and
lower molars; hypocone usually added in upper molars
2. The Strepsirhines
- with postorbital bar present on the skull; grasping thumb and big toe (higher degree of arboreal
adaptation); auditory capsule (ear region) specialized
- include Adapids, Lemurs (Old World tropics; small, arboreal, nocturnal, furry, with fox-like
face) and Lorises
3. The Haplorhinines (Tarsiiformes)
- ectotympanic bone forms a tube leading outward from the auditory bulla in these and higher
primates
- includes Omomyids (Eocene-Miocene) and Tarsiids (Lower Oligocene-Recent)
4. Anthropoids
- monkeys, apes and man (late Eocene - Recent)
- Late Eocene and early Oligocene with sharp increase in seasonality and reduced temperatures in
PALEO LECTURE, PAGE 137
north temperate zones (number of fossil primates drop); Later Cenozoic with fossil primates
almost totally limited to southern Asia, Africa and South America and consist almost entirely of
anthropoid primates
- probably omomyid ancestry
- with derived features of skull; never more than three bicuspid premolar teeth; upper molars
usually with quadrate pattern (cusps in "square" pattern); braincase expanded and foramen
magnum (where the backbone connects to the skull) tends to be under the skull (therefore face is
turned forward almost at a right angle to the backbone); two halves of the jaw are fused
a. New World Platyrrhines (Ceboids) - marmosets and cebid monkeys; most primitive
anthropoids; flat noses with paired but well-separated outwardly directed nasal openings; dental
formula I2/2 C1/1 P3/3 M3/3; Oligocene to Recent
b. Old World Catarrhines - Cercopithecid Monkeys and the Apes; protruding muzzle; nostrils
closer together and open forward and downward; dental formula I2/2 C1/1 P2/2 M3/3; upper
molars quadrangular, high-crowned, bilophodont
- substantial changes in global climates during Miocene due to northward movement of the
African plate (created Antarctic Circumpolar Current with savannah becoming dominant);
catarrhines did well, other primates didn't
c. Hominoids
- early types include small-bodied, long-faced Propliopithecidae (most primitive group),
Proconsulidae (African Dryomorphs) and Dryopithecidae (European Dryomorphs)
- Ramamorphs (ancestral to orangutan), Pongids (orangutan, chimpanzee, gorilla), hylobatids
(gibbons) often arboreal; pongids with canines enlarged, dental arcade U-shaped with molars in
two parallel rows (tooth row of man is hyperbolic)
- based primarily on DNA evidence, it has been theorized that at approximately 5-6 Ma gorillas,
chimps and hominids (man's family) diverged when climate became cooler, drier and more
seasonal (termed the Messinian Climate Crisis)
- However, recovery of a 6-7 Ma year old skull with a human-like face from northern Chad,
Africa (Sahelanthropus tchadensis) may indicate that the divergence of humans from other apes
occurred at 8 to 10 Ma
c1. The Hominidae
- there are many competing classifications of this family but this is one interpretation:
c1a. Australopithecines
- the first "humans"
- Ardipithecus species were the earliest known australopithecines, including Ardipithecus
kadabba (ca. 5.7 Ma?) and Ardipithecus ramidus (ca. 4.5-4.3 Ma) from Ethiopia, Africa; consist
of gracile (lightly-built) australopithecines with chimp-sized brains that inhabited woodlands
- Ardipithecus was bipedal (as indicated by the pelvis and leg structure) but the “big toe” on the
foot was divergent (the foot could be used for “grasping”), suggesting Ardipithecus may have
nested and fed in trees
PALEO LECTURE, PAGE 138
- Australopithecus species (ca. 4-2 Ma) were gracile (lightly-built) hominids; fully bipedal
(determined by hips, thigh bones and fossil footprints at Laetoli); very apelike in most of skeleton
with long arms and fingers; the brain is chimp-size (400-500 milliliters); moderate to marked
sexual dimorphism (males larger than females); height from 1.0 to 1.5 meters (3' 3" to 4' 11") and
weight from 30 to 70 kilograms (66 to 154 pounds); a "gracile" australopithecine probably lead to
Homo
- Paranthropus species (2.6-1.2 Ma) were robust (heavily-built) australopithecines; relatively
long arms; height 1.1 to 1.4 meters (3' 7" to 4' 7") and weight 40 to 80 kilograms (88 to 176
pounds); marked sexual dimorphism; prominent crests on top and back of skull; very long, broad,
flattish face; strong facial buttressing; very thick jaws; small incisors and canines; large, molarlike premolars; very large molars; brain size 410 to 530 milliliters
c1b. Homo
- the genus containing modern man
c1b1. Early Homo Species
- Homo rudolfensis (ca. 2.5 - 1.9 Ma) and Homo habilis (ca. 2.1 - 1.5 Ma) were similar to
Australopithecus but brain size increased to about 650-750 ml
The Oldowan Culture
- first tool culture; although the Oldowan Culture has considered to be a "pebble tool" culture,
their primary use appears to have been as choppers, scrapers and pounders; the Oldowan Culture
was probably due to Australopithecus gahri, Homo rudolfensis, H.habilis and early H. ergaster
- dates at 2.5 - 1.5 Ma; early humans used these tools for "expanding their niche" - cutting,
crushing, digging, projectiles and carrying; it appears that the hominids had no preconceived
shape of the tool during manufacture (i.e., no "mental template")
- early Homo species may have lived in multi-male and multi-female groups; males competed for
access to females
- no evidence of intentional burials, grave goods, art, etc.; no clear evidence of architectural
features
c1b2. Homo ergaster
- approximately 1.9 to 1.5 Ma in eastern Africa
- may be ancestral to all subsequent Homo species
- the slender-bodied, long-legged "Turkana Boy" skeleton is essentially modern and with a highly
efficient striding structure; adults probably 1.8 meters tall (6') or more; brain size 800- 1050 ml
- oldest H. ergaster made Oldowan tools; at approximately 1.65 Ma developed Acheulian
industry (with large hand-held stone axes); may have been first to use fire at 1.7 Ma (fire
provides warmth, used in hunting, protection against predators, remove toxins from food)
c1b3. Homo erectus
- Asiatic form [ca. 1.5 Ma to 225 Ka] with a relatively large brain (850 -1150 ml), flat skull, large
PALEO LECTURE, PAGE 139
brow ridges, sloped forehead, nuchal crest on back of skull, almost no chin; probably did not give
rise to later Homo species
c1b4. Origin of Homo sapiens
- probably evolved from H. ergaster-like species
- by 500 - 200 Ka with forms intermediate between H. ergaster/"erectus" and H. sapiens
Origin Theories for Homo sapiens include:
- Multi-Regional Hypothesis - evolution from several "stocks" of migrated Homo ergaster /
"erectus" (especially Africa and eastern Asia)
- Out-of-Africa Hypothesis - evolution from a single stock of H. ergaster / "erectus" that later
migrated (most popular theory) and replaced older groups
- Homo floresiensis, a tiny (adults 42 inches high!) island species from Indonesia, is similar to
Homo ergaster ; it may have lived as late as 18,000 years ago (if true, this greatly changes our
ideas of the diversity and distribution of ancient hominids)
c1b5. Homo neanderthalensis
- “early pre-Neandertals” at 400 Ka; Homo neanderthalensis at 150 Ka to 27 Ka; mostly lived in
Europe and western Asia
- often massive brow ridges; large cheek bones; protruding face; no chin; "bun"-shaped skull;
large cranial capacity (often greater than modern man); short (1.5 meters; 5 ft.) but very powerful
- probably not ancestral to Homo sapiens (with distinct DNA)
- hand axes decline, flake tradition becomes dominant
Mousterian Tradition
- usually attributed to Homo neanderthalensis
- strike flake from underside of a prepared "tortoise-shell" core to create many tool types; many
of these were Composite Tools (artifacts made from more than one component)
c1b6. Homo sapiens sapiens
- Homo sapiens sapiens evolved from archaic H. sapiens in Africa and then replaced
neanderthals in Eurasia?
- there may have been an early dispersal of anatomically modern-looking Homo sapiens from
Africa at about 100 Ka; there may have been a substantial “bottleneck” of population after that,
with numbers dropping to as low as 10,000 individuals
- Homo sapiens sapiens developed the Upper Paleolithic tool technology (35 to 9 Ka); often
typified by "punch-struck" blade industries (a blade is a long flake); these were "specialized"
hunter-gatherers (concentrate on a few resources) that often hunted herd animals
Religion - Burials with ceremonial burials and grave goods
Upper Paleolithic Art - first widespread production of true art was by modern Homo sapiens (Ex.
= cave paintings), probably with a religious significance
PALEO LECTURE, PAGE 140
----------------------------------------D. Order Rodentia
- rodents and rabbits are sister groups; often placed in the Superoder Glires
- rodents include squirrels, rats, mice and guinea pigs
- approximately 40% of all known modern mammalian species (over 2,000 living species);
approximately 50 families evolved in the Cenozoic (approximately 1/4 of these are extinct)
- probably evolved from anagalids (as did the lagomorphs)
1. Ecology and Distribution
- found on all continents except Antarctica and in nearly all habitats; mostly terrestrial, small
scampering quadrupeds with claws, long tails and whiskers
2. Osteology
a. Postcranial skeleton
- has not changed much from the primitive condition
b. Skull and teeth
- are much modified for gnawing; one pair of incisor teeth in upper jaw and one pair in lower
jaw; teeth curved and continually growing; incisors with two layers of hard enamel present only
on front face (edge behind wears away more rapidly and tooth stays sharp); diastema posterior to
incisor teeth
- usually four grinding teeth (P4-M3) posterior to diastema; many tooth patterns developed
- masseter muscle (one that closes the jaw) enlarged and inserts onto flange of mandible below
and behind teeth; masseter attachment patterns are important in rodent classification
E. Order Lagomorpha
- include pikas, rabbits and hares; late Paleocene to Recent; probably derived from anagalids
- herbivores; feed on grasses in the plains and on shrubs in rocky tundra and desert terrains
- two pairs of persistently-growing incisors (one pair behind the other) in upper jaw and enamel
completely surrounds the tooth; only one layer of enamel on anterior surface of incisors (two
layers in rodents)
F. Carnivorous Mammals
1. "Creodonts" ("Order Creodonta")
- probably polyphyletic, but some members were ancestral of the "true carnivores"
- dominant Tertiary carnivores; on all continents except Australia and South America; with
approximately 50 genera known from two families; carnassials usually involving M1+2/M2+3
(modern carnivores with carnassials at P4/M1); shorter limbs, unfused wrist bones, terminal
phalanges with fissured claws, usually no loss of toes versus true carnivores
- includes mustelid- and felid-like Oxyaenids and sabretooth cat-, dog- or hyaena-like
Hyaenodontids
PALEO LECTURE, PAGE 141
2. Carnivora Vera or "True Carnivores" (Order Carnivora)
- includes the order of modern carnivores
- was relatively minor part of faunas in Paleocene and early Eocene; late Eocene with canid
(dog), viverrid (civet) and possibly mustelid (weasel, stoat, mink, marten, skunk, badger and
otter) lines
a. General Features
- usually simple digestive system and conservative dentition (usually 3/3 1/1 4/4 2/3) with upper
canine enlarged and last upper premolar and first lower molar form carnassials; often reduce or
lose clavicle ("collar bone") and wrist bones fused [related to cursorial ("running") locomotion]
- type of ossification of auditory bulla is important in classification (including elements which
make up bulla and presence or absence of a bony septum dividing the bulla)
b. Classification
- have been divided into the Fissipedia (land dwellers) and Pinnipedia (seals and walruses) but
does not reflect the true phylogenetic relationships of the Carnivora
Most important groups of the Carnivora include:
b1. Arctoidea (Canoids; Caniformia)
- include the Canidae, Amphicyonidae, Procyonidae, Ursidae, Mustelidae and the Marine
Carnivores; internal carotid remains an important artery and the auditory bulla is not clearly
divided into two chambers
- believed to have been derived from the primitive miacine carnivores
- Canids (Family Canidae) - includes the dogs, foxes, wolves, and jackals; usually savannah
cursorial carnivores; good carnassial dentition and retain crushing teeth behind these; long limbs,
digitigrade feet (walk on toes with the heels not touching the ground); mostly social animals;
Eocene - Recent
- Amphicyonids or Bear-dogs (Family Amphicyonidae) - successful bear-like canoid stock;
Eocene - Pliocene
- Ursids (Bears) - probably evolved from canids during the Miocene; posterior teeth form
crushing surface for omnivorous diet; plantigrade feet (walk on the soles of the feet)
- Procyonids - includes the raccoons, kinkajou, coatis and their kin; small, arboreal omnivorous
types; carnassials lose shearing function; plantigrade feet
- Mustelids - includes skunks, weasels, badgers, wolverines and otters; usually small northern
temperate forms with short stocky limbs and no loss of toes; no septum in the auditory bulla;
good carnassials; sometimes placed within a separate lineage (Musteloids) versus dogs, raccoons
and bears; Oligocene - Recent
--------------------------------------------------------------------b2. Aquatic Families (the "Pinnipedia")
- enaliarctids, desmatophocids, otariids, odobenids and phocids are usually grouped in the
Suborder Pinnipedia but study of ear region indicates that phocoids (seals) and otaroids (the other
four families) had diphyletic (separate) origins from terrestrial carnivores
- Odobenids - walrus and kin; simplified cheek teeth with only a single root; derived types with
PALEO LECTURE, PAGE 142
tusks (for prying clams); Miocene - Recent
- Otariids - sealions, eared seals and fur seals; hind legs capable of positioning anteriorly for
locomotion on land; cheek teeth with single cusps; Miocene - Recent
- Phocids - include the "earless" seals; hind legs always posteriorly positioned; cheek teeth
double rooted and with accessory cusps; fossil record poor, but may be more kin to "musteloids"
than "canoids"; Miocene - Recent
---------------------------------------------------------------------------b3. Aeluroids (Feloids)
- includes viverrids, felids and hyaenids; main branch of internal carotid artery reduced or lost;
external carotid with countercurrent exchanger in the vicinity of the orbit for cooling blood
entering the brain
Viverroids - include viverrids (civets), herpestids (mongooses), hyaenids (hyaenas) and felids
(cats); have a septum in the auditory bulla
Felids - cats; most are small to medium-sized and live on a diet of rodents; range worldwide
except for Australia; digitigrade (digits bear weight) with a flexible skeleton, sharp retractile
claws; carnassials extremely well-developed; include "true cats" and "sabre-tooths" (are not
monophyletic groups)
G. Early Rooters and Browsers
- earliest herbivores were mostly Paleocene and Eocene; from rabbit- to elephant-sized; probably
most were rooters or feeders on tubers (with clawed feet, large canines and broad, low crowned
cheek teeth; typically complete dentition with no diastema)
- includes the pig-like Taeniodonts, semiaquatic Pantodonts, massive herbivorous Dinocerata
(the "Uintatheres"), the large clawed-footed Tillodonts, the rhino-sized Embrithopods, and the
"Condylarths" (ancestral to all other herbivorous groups; includes the
arctocyonids,hyopsodontids, and phenacodontids)
H. South American herbivores
1. Geologic and Paleontologic History of South America
- from Paleocene until Pliocene was an "island continent"
- South American mammalian evolution can be divided into three phases:
a. Late Eocene with marsupials, edentates and condylarths
b. Early Oligocene through late Miocene with marsupials and edentates radiating into many
adaptive niches and condylarths diversify into six orders and about 25 families; also with
primates and rodents reaching South America during the early Oligocene by "rafting" from North
America or West Africa
c. Great Faunal Interchange during Plio-Pleistocene with faunas migrating north and south
across Central America (South America received mastodonts, horses, tapirs, peccaries, camels,
deer, shrews, hares, squirrels, mice, dogs, bears, raccoons, otters and cats; all of the South
American taxa became extinct and these are the critters discussed below!)
- South American herbivores probably derived from didolodont condylarths
PALEO LECTURE, PAGE 143
2. Order Litopterna
- primitively with complete dental series; no diastema; upper molars with low cusps; trigonid and
talonid on lower molars nearly the same height
- includes the rabbit-like Adianthids, the horse-like Prototheriids, and the weird camel-like,
trunk-bearing Macraucheniids
3. Order Notoungulata
- largest order of South American herbivores (4 suborders, 13-14 families and over 100 genera);
late Paleocene to Pleistocene; also known from late Paleocene-early Eocene of Wyoming, China
and Mongolia
- notoungulates with short skulls, flattened above with a broad braincase; ear region develops two
chambers; early types with 44 low-crowned teeth; later types form diastema with high-crowned
molars with pi-shaped lophs; feet are mesaxonic (the third digit forms the axis) with reduction of
the lateral digits; most feet were hoofed
- most important groups are the rodent-like Typotheres; the horse-, chalicothere- or rhino-like
"bow toothed" Toxodonts; the rhino-like semiaphibious(?) Astrapotheres; and the short-limbed
pig- or tapir-like Pyrotheres
I. The "Edentates"
- A polyphyletic group including the pangolins, armadillos, anteaters, sloths and the extinct
palaeanodonts (but see below for probable phylogenetic relationships)
- reduction or loss of dentition (if retained teeth lack enamel); most with large claws (especially
on forelimbs) used for digging; diet often consists of ants, termites and small insects; living
members with muscular, gizzard-like portion of stomach for crushing prey
1. Xenarthrans (Order Xenarthra)
- include tree sloths, anteaters and armadillos and the extinct glyptodonts and ground sloths
- with accessory area of attachment on pelvic girdle; most with extra vertebral articulations (=
xenarthra; probably initially for digging; later supported carapace/shell in some groups), scapula
(shoulder blade) with two parallel spines; feet usually bear large claws, some genera with
ossicles (bony plates) in the skin and others with a bony shield over the body; modern
xenarthrans with variable body temperature which is lower than in other placentals
a. Infraorder Loricata (Cingulata)
- includes the Dasypodidae (armadillos; probably ancestral to other xenarthrans; Paleocene Recent) and the Glyptodontidae (Middle Eocene (?) Miocene - Pleistocene age; often huge,
armadillo-like)
b. Infraorder Pilosa
- includes the Bradypodidae (tree sloths) and the Ground Sloths (Oligocene - Pleistocene; from
cat-sized to over six meters long; includes the Mylodontoidea and Megalonychoidea) and the
Myrmecophagidae [true anteaters; Eocene (from Germany!) to Recent ]
2. Other "Edentates"
- include Pholidota (pangolins; with "pine cone-like" scales; Eocene - Recent; molecular data
PALEO LECTURE, PAGE 144
indicates that these are actually a sister group of carnivores!); Tubulidentata (aardvarks; Miocene
- Recent; molecular data indicates kinship to tenrecs, golden moles and elephant shrews) and
Palaeanodonta (include Lower Tertiary mole-like and sloth-like forms)
J. Order Proboscidea
-include the elephants; Eocene - Recent
1. Relationships of the Afrotheria (Afrotheres)
- recent cladistic studies suggest the existence of two clades of afrotheres; one that includes the
aardvarks (Tubulidentata), tenrecs (Tenrecoidea) and elephant shrews (Macroscelidea); and
another that includes the "Tethytheres" [elephants (Proboscidea), hyraxes (Hyracoidea) and
dugongs/manatees (Sirenia)]
2. General Characteristics of the Proboscidea
- overall evolutionary trends include increase in size; cheek teeth trend towards cyclic succession
and enlarged crown volume; enlargement of second incisor teeth as tusks (first for food gathering
and later for display); development of proboscis (nasal opening is posterior) with increased
shortening of the neck
3. Evolutionary History and Classification of Elephants
- may be derived from phenacodontid condylarths; Geologic Range = Eocene- Recent
- most important groups are the Deinotheroidea (with downturned and backwardly curved tusks)
and the Euelephantoidea [include the Mammutidae (mastodonts), Gomphotheridae ("shoveltuskers") and the Elephantidae (elephants and mammoths)]
K. Order Sirenia
- manatees and dugongs
- totally aquatic, huge (up to 8 meters long) shapeless animals with a large tail (the "swim fin"),
small front flipper, blunt mouth with thick overhanging lips; skeletal adaptations for aquatic life
include pelvic girdle reduced to a vestige and thick, dense ribs; Eocene - Recent
L. Order Desmostylia
- pony-sized aquatic animals with short, stout limbs and short shovel-like tusked mouth; each
cheek tooth made of cluster of stout dentine tubules; Upper Oligocene - Miocene
M. Order Acreodi (Mesonychids)
- difficult to classify (often placed close to the cetaceans and may have been ancestral to whales)
- descended from arctocyonid "condylarths"; may have been hyaenid-like bone-crushing
scavengers; include largest known land carnivores/scavengers
N. Order Cetacea
- include the whales
- mesonychids, whales, artiodactyls (cattle, antelopes, pigs, etc.) and perissodactyls (horses,
rhinos and tapirs) are related and often placed within the "Superorder Cetartiodactyla"
PALEO LECTURE, PAGE 145
1. General Characteristics of Cetaceans
- specialized for aquatic life with streamlined body; tail forms horizontal fluke for propulsion;
hind limb absent; fore limb forms short flipper for steering; thick fat layer; no sense of smell and
vision is poor but sense of touch and hearing very well-developed; brains large and complex;
primarily carnivores (feed on squid, fish or plankton)
- bones filled with oil (for flotation and energy reserve); snout elongate, rest of skull is telescoped
(maxillae may touch bones at back of braincase); no sacrum, typically no hind limb and only
remnant of pelvic bone; pectoral girdle lacks a clavicle, humerus short and paddle has four or
five digits, each with many phalanges
2. Classification of Whales
- includes three suborders - the Archeoceti (earliest whales; derived from mesonychids or
artiodactyls; Eocene - Oligocene, Miocene(?); includes the long-snouted, toothed "zeuglodonts");
Odontoceti (toothed whales including dolphins, porpoises, sperm and killer whales); Mysticeti
(include plankton-straining baleen whales; largest animals that ever lived)
O. Order Perissodactyla
- "odd toed" ungulates including tapirs, rhinoceroses, horses, brontotheres and chalicotheres
- derived from phenacodontid condylarths
- first appear in the Eocene (also peaked in the Eocene); good fossil record in North America and
Eurasia and later members found in Africa and South America
- axis of weight-bearing passes through the middle or third digit (mesaxonic); most members are
three toed but later horses eliminated the lateral digits to become one toed
- astragalus (ankle bone) with a single "pulley"; molar teeth with a lophodont pattern (with
enamel loops)
1. Suborder Ceratomorpha
- includes tapirs and rhinoceroses (develop cross-lophs on the teeth); include largest land
mammals known (Inthricotherines were rhinos up to 5.4 m at shoulder)
2. Suborder Ancylopoda
a. Superfamily Chalicotheroidea
- chalicotheres; Eocene-Pleistocene of North America, Eurasia and Africa; Moropus (Miocene,
North America) was horse-sized clawed bipedal browser
3. Suborder Hippomorpha - includes the horses and brontotheres
a. Superfamily Equoidea
- horses; Eocene-Recent
- evolutionary trends include increase in size and height, increased complexity of enamel pattern
on cheek teeth, elongation of legs, reduction of toes to one
b. Superfamily Brontotheroidea
- include the titanotheres (brontotheres); medium- to very large-sized herbivores of the early
PALEO LECTURE, PAGE 146
Tertiary of North America and eastern Asia; with w-shaped enamel ridges (ectoloph) on the
upper molars
P. Order Artiodactyla
- "even toed" ungulates; includes pigs, camels, giraffes, deer, antelope, goats, sheep, cattle and
other extinct and modern groups; with 79 living genera; 27 families from Cenozoic (10 survive);
derived from the arctocyonid condylarths
1. Morphology
- foot axis between the third and fourth digits (paraxonic); digits equal in size; metapodials often
fuse to form cannon bone; astragalus (ankle bone) forms double pulley structure
- primitive stocks (Ex.= pigs) with complete dentition and often with enlarged canine tusks; later
stocks with upper incisors reduced or lost, with a diastema, premolars become partially molarized
(i.e. molar-like)
- early stocks (palaeodonts and suiformes) with brachydont (low-crowned) and bunodont (with
low, rounded cusps) molars; all others with selenodont dentition (cusps crescent or half-moon
shaped)
- early stocks with swine-like, short limbs with fusion of the bones and little reduced lateral toes
- complex stomachs for digesting vegetation (pigs and hippos with 2 to 3 chambers; camels and
llamas with 3 chambers and ruminate; cattle and deer with four chambered stomachs and
ruminate)
- with origin in the Paleocene; first radiation in early Eocene gave rise to many pig-like stocks
(forest and woodland rooters and browsers); second radiation in late Eocene and early Oligocene
gave rise to early ruminants; in Miocene ruminants diversified to exploit the savannahs and
grasslands and remain the dominant herbivores there today
2. Classification
- include the "Palaeodonts" (Eocene primitive artiodactyls; probably polyphyletic), Suina
[Suiformes; include the pig-like entelodonts, peccaries (javelinas), true pigs, and hippos],
Tylopoda [cainotheres, xiphodonts, merycoidodonts (= oreodonts; the most successful extinct
tylopod group; pig- or sheep-like), agriochoerids, camelids (camels first evolved in North
America; include many diverse extinct types) and protoceratids (deer-like; often with weird
"nose" horns)], and the Ruminantia [include the Traguloids (chevrotains, musk deer) and the
Pecora (includes the higher ruminants; cattle, deer, giraffes and antelope; with development of
various paired "horns"; with ossicones in giraffes, antlers in deer and horns in cattle, antelopes,
goats, sheep, etc.; often with fused limb bones)]