Natural History of (Terrestrial) Vertebrates
Chapter #1 – The Diversity, Classification, and
Evolution of Vertebrates
Introduction to Vertebrates
Phylogenetic
systematics
(cladistics)
What is a Vertebrate?
Common
Ancestor
Answer:
Classification of organisms that share similar derived characteristics
Domain: Eukarya (Eukaryotic cells = “true nucleus”)
Kingdom: Animalia (Multi-cellular heterotrophs)
Phylum: Chordata
•
•
•
•
Notochord (Flexible rod; skeletal support)
Dorsal, hollow nerve cord (Brain / spinal column)
Pharyngeal slits (openings in throat; water passage)
Muscular, post-anal tail (Balance / propulsion)
Subphylum: Urochordata
• Tunicates (sea squirts)
Subphylum: Cephalochordata
• Lancelets
Introduction to Vertebrates
Phylogenetic
systematics
(cladistics)
What is a Vertebrate?
Common
Ancestor
Answer:
Classification of organisms that share similar derived characteristics
Domain: Eukarya (Eukaryotic cells = “true nucleus”)
Kingdom: Animalia (Multi-cellular heterotrophs)
Phylum: Chordata
•
•
•
•
Increased body size
and activity level
Notochord (Flexible rod; skeletal support)
Dorsal, hollow nerve cord (Brain / spinal column)
Pharyngeal slits (openings in throat; water passage)
Muscular, post-anal tail (Balance / propulsion)
• Vertebral column present (bone / cartilage)
Subphylum:
Vertebrata
• High degree of cephalization
• Cranium; tripartite brain; multi-cellular sense organs
• Specialized organ systems
• e.g., closed circulatory system; specialized kidneys
Classification of
Vertebrates:
Introduction to Vertebrates
• 57,000 species (100x extinct)
• New discoveries weekly
Introduction to Vertebrates
Giant Forest Hog
(Kenya – 1904)
Bonobo
(Congo – 1929)
Komodo Dragon
(Komodo - 1912)
Giant Panda
(China – 1932)
Coelocanth
(Deep Sea – 1998)
Megamouth
(Deep Sea - 1976)
Saola
(Vietnam - 1992)
Introduction to Vertebrates
Present
~ 5 mya
ERA
PERIOD
Cenozoic
Earth History Critical for Understanding Natural History of Vertebrates:
Quaternary
~ 65 mya
~ 205 mya
Cretaceous
Mesozoic
~ 145 mya
~ 250 mya
~ 440 mya
~ 490 mya
~ 540 mya
Triassic
Carboniferous
Paleozoic
~ 420 mya
Jurassic
Permian
~ 290 mya
~ 350 mya
Tertiary
Devonian
Silurian
Ordovician
Cambrian
Precambrian
~ 4,600 mya
Introduction to Vertebrates
The Paleozoic world very different from the one we currently know:
ERA
PERIOD
Cenozoic
Present
Quaternary
Tertiary
~ 65 mya
Mesozoic
Cretaceous
Jurassic
Triassic
~ 250 mya
Permian
• 6 major land masses including Laurentia (North America)
and Gondwana (Current Southern Hemisphere countries)
Paleozoic
Carboniferous
Devonian
Climate:
Silurian
• Sea levels at / near all-time high; high levels of CO2
• Greenhouse Effect: hot & dry climate
Ordovician
Cambrian
Precambrian
Continental Geography:
~ 540 mya
Terrestrial Ecosystem (unsuitable conditions…):
• Wet habitat = algae / lichens / fungi
• Land = green algae
Introduction to Vertebrates
The Paleozoic world very different from the one we currently know:
ERA
PERIOD
Continental Geography:
Cenozoic
Present
Quaternary
Continents beginning
to drift together
Tertiary
~ 65 mya
Mesozoic
Cretaceous
Gondwana
(south pole)
Jurassic
Triassic
Laurasia:
Laurentia + Baltica + Siberia
~ 250 mya
Permian
(along equator)
Paleozoic
Carboniferous
Climate:
Devonian
• Cooler, moister conditions than Cambrian
Silurian
• Major glaciations; falling CO2 levels
Ordovician
Cambrian
Precambrian
Terrestrial Ecosystem:
~ 540 mya
• Stratified forest communities of vascular plants (wet places…)
• Terrestrial animals = millipedes / springtails / mites
• No terrestrial vertebrates
Introduction to Vertebrates
The Paleozoic world very different from the one we currently know:
ERA
PERIOD
Continental Geography:
Cenozoic
Present
Quaternary
Tertiary
Continents drift together
to form Pangaea (Permian)
~ 65 mya
Mesozoic
Cretaceous
(36% of Earth’s surface)
Jurassic
Triassic
~ 250 mya
Permian
Figure 7.4
Paleozoic
Carboniferous
Climate:
Devonian
• Climate highly differentiated across super-continent
Silurian
• Due to glaciations (also oscillated sea levels)
Terrestrial Ecosystem:
Ordovician
Cambrian
Precambrian
• Broadleaf forests appear (similar in appearance to those today)
~ 540 mya
• Gymnosperms – not angiosperms
• Arthropods flourished (Detritivores / herbivores / carnivores)
• Terrestrial vertebrates appear / diversify (non-amniotes / amniotes)
Introduction to Vertebrates
Present
~ 5 mya
ERA
PERIOD
Cenozoic
Earth History Critical for Understanding Natural History of Vertebrates:
Quaternary
~ 65 mya
~ 205 mya
~ 250 mya
~ 440 mya
~ 490 mya
~ 540 mya
Devonian
Silurian
Ordovician
Cambrian
Precambrian
~ 4,600 mya
Age of Dinosaurs
Triassic
Carboniferous
Paleozoic
~ 420 mya
Jurassic
Permian
~ 290 mya
~ 350 mya
Diversification of mammals and birds (~ 57 mya)
Cretaceous
Mesozoic
~ 145 mya
Tertiary
First reptiles (~ 300 mya)
First amphibians (~ 370 mya)
Diversification of fish (~ 420 mya)
Introduction to Vertebrates
Earth History Critical for Understanding Natural History of Vertebrates:
Continued continental drift strong influence on vertebrate evolution:
1) Climate:
• Location of land masses (Mesozoic = tropical / Cenozoic = temperate)
• Ocean circulation (e.g., arctic ocean isolated = lack of warm currents)
• Sea level (epicontinental seas = maritime climate inland)
Western Interior
Sea
Introduction to Vertebrates
Earth History Critical for Understanding Natural History of Vertebrates:
Continued continental drift strong influence on vertebrate evolution:
1) Climate:
• Location of land masses (Mesozoic = tropical / Cenozoic = temperate)
• Ocean circulation (e.g., arctic ocean isolated = lack of warm currents)
• Sea level (epicontinental seas = maritime climate inland)
2) Land Bridges
• Connections of land between continents (attach / detach)
Marsupial Migration
Bering Land Bridge
(e.g., human migration)
Introduction to Vertebrates
Present
~ 5 mya
ERA
PERIOD
Cenozoic
Earth History Critical for Understanding Natural History of Vertebrates:
Quaternary
~ 65 mya
~ 205 mya
~ 250 mya
~ 440 mya
~ 490 mya
~ 540 mya
Triassic
Carboniferous
Paleozoic
~ 420 mya
Jurassic
Permian
~ 290 mya
~ 350 mya
Devonian
Silurian
Ordovician
Cambrian
Precambrian
~ 4,600 mya
Mass
Extinction
Cretaceous
Mesozoic
~ 145 mya
Tertiary
History of life punctuated by mass extinctions:
• 90% marine species
Extensive
Diversification
Permian Mass Extinction
• Massive volcanic eruptions in Siberia (lava flows
= ½ area of United States)
• Gas release = Global warming (~ 6º C)
Underwater Methyl hydrate melting
Positive
Feedback
Methane release
Global environment disrupted
(100,000’s years)
Introduction to Vertebrates
Present
~ 5 mya
ERA
PERIOD
Cenozoic
Earth History Critical for Understanding Natural History of Vertebrates:
Quaternary
~ 65 mya
~ 205 mya
~ 250 mya
~ 440 mya
~ 490 mya
~ 540 mya
Jurassic
Triassic
Carboniferous
Paleozoic
~ 420 mya
Devonian
Silurian
Ordovician
Cambrian
Precambrian
~ 4,600 mya
Extensive
Diversification
Permian
~ 290 mya
~ 350 mya
Mass
Extinction
Cretaceous
Mesozoic
~ 145 mya
Tertiary
History of life punctuated by mass extinctions:
• 90% marine species
• 50% marine species; dinosaurs
The K - T Meteorite: Permian Mass Extinction
“A dinosaur’s worst nightmare…”
• Massive volcanic eruptions in Siberia (lava flows
= ½ area of United States)
If a 10km diameter object impacted at the point at
• Gas release = Global warming (~ 6º C)which it struck it would have a velocity of roughly
100,000 km/h. At this velocity there would have been
an initial blast which would have destroyed everything
Underwater hydrate meltingwithin a radius of between 400 and 500 km. At the
same time large fires would have been started by the
intense shock wave which would have traveled long
distances. Trillions of tons of debris (dust, gases and
Methane release
water vapour) would have been thrown into the
atmosphere when the object vaporized. Many
enormous tidal waves would be started. Along with
the tidal waves the blast would also start a chain
reaction of earthquakes and volcanic activity. There
would have also been very high winds caused by the
blast. In the days and weeks following the impact the
cloud of debris would have been carried over large
distances by the post blast high winds. This will have
caused months of darkness and a decrease in global
temperatures. After this there would have been an
increase in temperatures caused by the large amounts
of CO2 released by what would have been global fires.
Global
environment disrupted
Eventually this would cause chemical reactions that
would (100,000’s
result in the years)
formation of acid rains.
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
• Earliest vertebrate fossils located in marine sediment
• All non-vertebrate chordates / other deuterostomes exclusively marine
Gnathostomes (“jawed mouth”)
(mid Ordovician period)
Life History:
Agnathans (“jawless” vertebrates)
• Entirely marine
• Bottom-dwelling scavengers
Morphology:
Retains primitive vertebrate features
• Round, jawless mouth
(e.g., [body fluid] similar to [seawater])
• Elongated, scale-less
• Degenerate eyes; tentacles
Hagfish (Myxinoidea)
• Slime glands (flanks)
(Carboniferous* period)
• Anti-predator (gels H2O)
1st Vertebrates
(early Cambrian period)
Feed via tearing
off tidbits…
Introduction to Vertebrates
Yummmm…
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
• Earliest vertebrate fossils located in marine sediment
• All non-vertebrate chordates / other deuterostomes exclusively marine
Gnathostomes (“jawed mouth”)
(mid Ordovician period)
Life History:
Agnathans (“jawless” vertebrates)
• Entirely marine
• Bottom-dwelling scavengers
Retains primitive vertebrate features
Morphology:
(e.g., [body fluid] similar to [seawater])
• Round, jawless mouth
Table 3.1 – Vertebrate Life
• Elongated, scale-less
• Degenerate eyes; tentacles
Hagfish (Myxinoidea)
• Slime glands (flanks)
(Carboniferous* period)
• Anti-predator (gels H2O)
• Cartilaginous skeleton
• Lack vertebrae
 Harvested for skin
(“eel-skin” leather)
1st Vertebrates
(early Cambrian period)
Feed via tearing
off tidbits…
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
• Earliest vertebrate fossils located in marine sediment
• All non-vertebrate chordates / other deuterostomes exclusively marine
Gnathostomes (“jawed mouth”)
Agnathans (“jawless” vertebrates)
(mid Ordovician period)
Life History:
• Marine / Freshwater (anadromous)
Lamprey (Petromyzontoidea)
• Parasites (fluid-feeders)
(Carboniferous* period)
Hagfish (Myxinoidea)
(Carboniferous* period)
1st Vertebrates
(early Cambrian period)
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
• Earliest vertebrate fossils located in marine sediment
• All non-vertebrate chordates / other deuterostomes exclusively marine
Gnathostomes (“jawed mouth”)
Morphology:
(mid Ordovician period)
• Round, jawless mouth
Agnathans (“jawless” vertebrates)
• Elongated, scale-less
• Cartilaginous skeleton
• Vertebral elements present
Life History:
• Marine / Freshwater (anadromous)
Lamprey (Petromyzontoidea)
• Parasites (fluid-feeders)
(Carboniferous* period)
Hagfish (Myxinoidea)
(Carboniferous* period)
 Devastated Great
Lakes fisheries
1st Vertebrates
(early Cambrian period)
Introduction to Vertebrates
Derived Features of Gnathostomes:
1) Jaws:
Suspension feeders / Parasites
Expansion of pharynx;
Mouth closure to prevent food escape
Raptorial feeders
• Derived from anterior branchial arches (gill supports)
• Benefits: 1) New feeding behaviors (e.g., grasping / biting / tearing)
2) New food resources (e.g. herbivory)
3) Manipulation of environment (e.g., digging holes / carrying objects)
4) Improved gill ventilation (primary driving force?)
2) Paired Appendages:
• Benefits: 1) Control of body position (primarily pitch) in water (active, predatory fish…)
2) Defense (spines); Behavior (e.g., reproductive)
Stonefish
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
Tetrapods (“jawed mouth”)
(late Devonian period)
Gnathostomes (“jawed mouth”)
(mid Ordovician period)
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
Tetrapods (“jawed mouth”)
Life History:
(late Devonian period)
• Primarily marine
• Suspension feeders / carnivores
• Internal fertilization
Morphology:
• Cartilaginous endoskeleton (derived)
• Scales (Placoid)
• Well developed jaws / paired fins
1) Sharks
• Fusiform (powerful;  maneuverability)
• Acute vision / smell
Chondricthyes (“Cartilage fish”)
(late Silurian period)
Gnathostomes (“jawed mouth”)
(mid Ordovician period)
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
Tetrapods (“jawed mouth”)
Life History:
(late Devonian period)
• Primarily marine
• Suspension feeders / carnivores
• Internal fertilization
Morphology:
• Cartilaginous endoskeleton (derived)
• Scales (Placoid)
Skate
• Well developed jaws / paired fins
2) Skates / Rays
• Flattened, bottom dwellers
• Enlarged pectoral fins (“fly” through H2O)
Chondricthyes (“Cartilage fish”)
Gnathostomes (“jawed mouth”)
(mid Ordovician period)
(late Silurian period)
Ray
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
Tetrapods (“jawed mouth”)
Life History:
(late Devonian period)
• Primarily marine
• Suspension feeders / carnivores
• Internal fertilization
Morphology:
• Cartilaginous endoskeleton (derived)
• Scales (Placoid)
• Well developed jaws / paired fins
3) Ratfish (Chimera)
• Deep water dwellers
Chondricthyes (“Cartilage fish”)
• Little known of natural history
(late Silurian period)
Gnathostomes (“jawed mouth”)
(mid Ordovician period)
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
Tetrapods (“jawed mouth”)
(late Devonian period)
Osteichthyes (“Bony fish”)
(late Silurian period)
Chondricthyes (“Cartilage fish”)
(late Silurian period)
Gnathostomes (“jawed mouth”)
(mid Ordovician period)
Introduction to Vertebrates
Early vertebrates believed to have evolved in marine environment:
Most diverse vertebrate
group (~ 30,000 species)
Tetrapods (“jawed mouth”)
(late Devonian period)
Osteichthyes (“Bony fish”)
(late Silurian period)
Life History:
• Marine / Freshwater
1) Ray-finned Fish (actinopterygii)
• Fins supported by flexible rods
• Increased maneuverability
1) Lobe-finned Fish (Sarcopterygii)
• Fleshy fins supported by bone
• “Walking” underwater
• Diverse feeding strategies
• External / Internal fertilization
Morphology:
• Ossified endoskeleton (Calcium phosphate)
• Flattened, bony scales
• Mucus glands (drag reduction / protection)
• Operculum (gill covering – stationary breathing)
• Swim bladder (motionless buoyancy)
Gnathostomes (“jawed mouth”)
(mid Ordovician period)
Introduction to Vertebrates
Demands of terrestrial life different than aquatic life…
1) Density: H2O is 800x denser than air (Ramification = support systems)
Fish:
• Remain neutrally buoyant (same density as H2O)
A) Swim bladder (Bony fish)
B) Store oils in liver (cartilaginous fish)
C) Store oils / lipids in swim bladder / body (Deep sea fishes)
Terrestrial Vertebrates:
• Require modified skeleton / musculature (counter gravity)
1) Bones designed for strength (compact bone) and weight (spongy bone)
2) Axial skeleton modifications (fish = flexibility)
• Vertebral processes (zygaphophyses) resist twisting & bending
• Distinct vertebral regions (e.g., lumbar = support vertebrae)
• Ribs stout and prominently developed
3) Axial muscles differentiated and enlarged (postural support)
4) Limb girdles enlarged; limb location shifted (e.g., under body)
Introduction to Vertebrates
Demands of terrestrial life different than aquatic life…
2) Viscosity: H2O has 18x viscosity of air
(Ramification = locomotion)
Fish:
Paired fins used for steering,
braking, and providing lift
• Have stream-lined shape (minimize drag)
• Small scales / loss of scales; mucus production
• Utilize undulations of body / tail to “push” against viscous water
1) Anguilliform
2) Carangiform
3) Ostraciiform
Majority of body undulates
Caudal region undulates
Caudal fin undulates
Terrestrial Vertebrates:
• Friction must be generated between limbs and ground:
• Primitive mode = axial flexion with limbs acting as holdfasts
• Lateral Sequence Gait: 3 of 4 limbs in contact with ground (tripod)
Introduction to Vertebrates
Demands of terrestrial life different than aquatic life…
2) Viscosity: H2O has 18x viscosity of air
(Ramification = locomotion)
• Friction must be generated between limbs and ground:
• Derived mode = limbs held underneath body (limb flexion)
Amble / Pace
Fore- and hind feet on same
side swung in unison
Avoid tangling of
long limbs
Keeps line of support
under center of gravity
Trot
Feet diagonally opposite
move in unison
Bound
All four limbs strike
ground in unison
Excellent stability;
Excellent clearance
Introduction to Vertebrates
Demands of terrestrial life different than aquatic life…
2) Viscosity: H2O has 18x viscosity of air
(Ramification = locomotion)
• Friction must be generated between limbs and ground:
• Derived mode = limbs held underneath body (limb flexion)
Ricochet
Two limbs strike ground
in unison
Half Bound
Hind legs strike together;
forelegs = lead / trail pattern
Gallop / Canter
Fore / hind feet show
lead / trail pattern
(asymmetrical)
Introduction to Vertebrates
Demands of terrestrial life different than aquatic life…
3) Oxygen Content: H2O contains ¼ [O2] of air (Ramification = respiratory systems)
Fish:
• Gills: Specialized respiratory structures for capturing O2
Flow of water unidirectional
(viscosity issues…)
• Buccal Pumping
• Ram Ventilation
Counter-current exchange ( efficiency)
• Lungs / Accessory Structures: ([O2] very low)
• Facultative Air Breathers = supplement gills as necessary
• Obligatory Air Breathers = must supplement gills or drown
Introduction to Vertebrates
Demands of terrestrial life different than aquatic life…
3) Oxygen Content: H2O contains ¼ [O2] of air (Ramification = respiratory systems)
Terrestrial Vertebrates:
• Air easier medium for respiration than water:
1) Low density / low viscosity = energetically feasible tidal ventilation
2) High [O2] = reduced volume of air needed to supply O2
• Ventilation strategies:
1) Positive Pressure: Air “swallowed”; pushed into lungs (shrink oral cavity)
2) Negative Pressure: Thoracic cavity expanded; air “pulled” into lungs
Introduction to Vertebrates
Sensory Systems:
Vision
Smell / Taste
Mechanical
Fish
B
B
A
Tetrapod
A
B
A
Tetrapods can
see further with
less distortion
Receptors in
head region detect
dissolved / volatilized
chemicals
Lateral line
System
Auditory
System
Left
Right
Introduction to Vertebrates
Introduction to Vertebrates
Sensory Systems:
Vision
Smell / Taste
Mechanical
Electroreception
Fish
B
B
A
A
Tetrapod
A
B
A
D
Tetrapods can
See further with
less distortion
Rely on hair cells
to detect vibrations
in water / air
Receptors in
head region detect
dissolved / volatilized
chemicals
Function:
Prey Location
Mate Identification
Water conducts
electricity – air
does not
Introduction to Vertebrates
Origin and Radiation of Tetrapods:
• Related to lobe-finned fish (sarcopterygians – lung fish)
• Anatomy suggests that early tetrapods were aquatic (e.g., internal, fish-like gills)
How does a terrestrial animal evolve in water?
Thoughts of foresight
not an option!
Stem Tetrapod (“four limbs”)
Acanthostega
(late devonian period)
Ichthyostega
Introduction to Vertebrates
Origin and Radiation of Tetrapods:
• Related to lobe-finned fish (sarcopterygians – lung fish)
• Anatomy suggests that early tetrapods were aquatic (e.g., internal, fish-like gills)
How does a terrestrial animal evolve in water?
Classic Theory:
Dries up
Migration
Problems: 1) Current lung fish cope with problem by estivating
2) New pond = continuation in aquatic lifestyle
Current Theory = Juvenile lob-finned fish aggregated in shallow-water habitats
• Limbs with digits / ankle / wrists = navigation / manipulation of bottom vegetation
• Strengthening of girdles = predatory lunges under water
• Development of distinct neck = lift snout out of water
Stem Tetrapod (“four limbs”)
Acanthostega
(late devonian period)
Ichthyostega
Introduction to Vertebrates
Origin and Radiation of Tetrapods:
Amniotes
Lissamphibians
(early Carboniferous period)
(major radiation = Permian)
(extant amphibians)
Majority extinct by mid Persian
(V) Table 9.1
?
Temnospondyl
(aquatic)
Pages 206 - 211
?
?
Lepospondyl
Batrachomorphs (“Frog form”)
Anthracosaur
(Terrestrial)
Reptilomorph (“Reptile form”)
Stem Tetrapod (“four limbs”)
(late devonian period)
?