PALEONTOLOGY LABORATORY I- PROTISTA, EUBACTERIA, ARCHEOCYATHIDS, PORIFERA &
CONULARIDS
Kingdoms EUBACTERIA and PROTISTA
Fossil organisms within the Kingdom Protista represent the earliest life forms known. These organisms
are characterized by a single-celled body plan and are contrasted to members of the Kingdom Eubacteria
(cyanobacteria) by having a nucleus. This lab concentrates on the protist phyla Foraminifera, Radiolarian,
Coccolithosphorids and Diatoms because many of their constituents have mineralized skeletons and an
extensive fossil record. Because of their wide-spread distribution and rapid evolutionary rates, many of
the protists are excellent index fossils used in biostratigraphic studies. You will become familiar with the
morphologic features and be able to identify each of the groups listed below, in addition to knowing their
geologic ages.
CLASSIFICATION & GEOLOGIC RANGES
Kingdom Eubacteria (Precambrian - Recent)
Group "stromatolites" (Archaen - Recent)
Kingdom Protista (Precambrian - Recent)
Phylum Granuloreticulosa
Class Foraminifera (Cambrian - Recent)
Group "fusulinids"(Late Paleozoic)
Group "nummulitids"(Early Cenozoic)
"planktonic forams" ( Cretaceous-Rec.)
Phylum Acrtinopoda
Class Radiolaria (Cambrian - Recent)
Phylum Chrysophyta
"diatoms" (Cretaceous - Recent)
Kingdom Eubacteria
"Stromatolites"
Stromatolites are organically produced sedimentary structures and are among the oldest fossils known on Earth (they occur in
Archean rocks 3.5 b.y. old). they are made by cyanobacteria (often erroneously called “blue-green algae”, however, because
the cells are prokaryotic, they should not be confused with true algae which are eukaryotes. Stomatolites are without skeletons
(they are layers of sediment), and differ from some similar-looking sponges that have a mineralized skeleton.
Class FORAMINIFERA
Foraminifera are the most common and geologically most important of the fossil protozoans. The name translates to porebearing and refers to the numerous perforations (foramina) in the skeleton walls. It is through the foramina that the organism
extends its pseudopod or protoplasm.
Today, nearly all forams live in marine environments and are either bottom dwellers (benthic) or float in the water column
(planktic). Forams are characterized by multi-chambered tests which are built by addition of new chambers during life.
Chambers are separated by partitions called septa (singular = septum), whose exterior expressions are termed sutures.
Composition of the tests are either calcite (CaCO3) or agglutinated (cemented foreign particles, e.g., sand or silt grains).
Agglutinated Foram
The classification of Foraminifera is based on (i) test microstructure, (ii) test symmetry, and (iii) aperture type.
Test Composition and Microstructure
Agglutinated (sometimes called arenaceous). These tests are composed of grains or fragments of foreign material cemented by
the organism and commonly have a sugary appearance. Occasionally grains of quartz and/or shell fragments can be seen.
Calcareous tests can either be hyaline which can be distinguished by their glassy appearance or porcelainous which are usually
white or opaque in color and resembles china or porcelain.
Figure !
Test symmetry
1. Uniserial. Chambers are added in a straight or curvilinear series. (see Figure 1 above)
2. Biserial. Chambers are added in an alternating fashion.
3. Triserial. Chambers are added every 120 o in a spiral fashion.
4. Planispiral. Chambers are added around the periphery and are coiled in a single plane. Planispiral tests are evolute when all
previous chambers are visible, and are involute when only the last spiral or whorl is visible.
5. Trochospiral. Chambers are added around the periphery, but each new chamber is slightly offset so that a very low spire or
cone results. The central part of the disc on the side of the aperture is called the umbilicus.
Ecology
During life, forams are either benthonic of planktic, relying on their pseudopodia for both locomotion and creating water
currents for food gathering. Benthic forms inhabiting shallow to deep water environments can be recognized by their larger
size, thick heavily ornamented walls, and less "globular" shape. Planktic forams are recognized by their thin, and often
perforated, tests and globular inflated chambers.
Larger Foraminifera
Several times during the history of Foraminifera, tests many times larger than you have been seen until now have evolved.
Although large tests are known from several foraminiferal families, only two, the fusulinids (Family Fusulinidae) and
nummulitids (Family Nummulitidae) are considered below.
Nummulites
The nummulitids existed during the Early Cenozoic and are famous for their abundance in limestones from which the Great
Pyramids of Egypt built. Their tests are planispiral and involute, and unlike the fusulinids, are coiled around the short axis.
The fusulinids were important benthic constituents of Late Paleozoic shallow seas. The tests of fusulinids are involute and
planispirally coiled about the long axis. The test walls of fusulinids are multi-layered in contrast to the microgranular tests of
other forams. An individual fusulinid can be seen in this image. Agood example of a fusulinid limestone can be seen in this
image.
Fusulinids
RADIOLARIA
Radiolarians are heterotroph protozoans which thrive in the upper layers of the seas. The protoplasm of radiolarians is
surrounded by a test commonly composed of an intricate lattice work of opaline silica (there are minor groups which construct
their tests of strontium sulfate a silica enriched with organic material). Like the foraminifera, radiolarians have pseudopodia
which protrude through the porous tests to aid in locomotion and food gathering. The tests of radiolarians exhibit great
morphologic diversity, but they are typically characterized by radial or spherical symmetry.
Radiolarians
Phylum CHRYSOPHYTA
"Diatoms"
Diatoms are a kind of microscopic golden-brown algae that secrete siliceous tests (sometimes called frustules) consisting of
two overlapping halves or valves that fit together. The walls of the tests are ornamented by pores, grooves, and ridges.
Diatoms occur in two basic forms: (i) the centric type in which the test has radial symmetry, and (ii) the pennate type in which
the test is elongate and has bilateral symmetry. An example of both types can be seen in this microscope image. The centric
type are planktic and predominantly marine, whereas the pennate type are mostly benthic and occur in fresh, brackish, and
shallow marine environments. Sometimes diatoms form a rock called diatomite, which is composed entirely of diatoms.
Diatomite often forms by a diatom "bloom" in nutrient-rich fresh-water lakes.
Diatoms
COCCOLITHOPHORES (calcareous nannoplankton) - you will not see the actual specimens in lab because they are too small
to see without an electron microscope
a.
Geologic range: Early Jurassic to Recent
b.
Shell composition: Calcite
c.
Size: 0.002 - 0.02 mm (2 - 20 µm). They are so small that they must be studied with an electron microscope. We will
look at photos in lab.
d.
Significance: The base of the marine food chain (phytoplankton); useful in biostratigraphy.
e.
Morphology: Organism is spherical to sub- spherical and covered by circular plates called coccoliths. Coccoliths may
resemble a button or a daisy with petal-like ornamentation around the edge.
f.
Environment: Marine only; exclusively planktonic.
Coccoliths (calcareous nannofossils).
Archeocyathids have been assigned by paleontologists to many different animal groups, primarily the corals and Pleosponges.
Many researchers even referred to them to a distinct, separate Phylum, Archeocyatha. Recent investigations have proved
pretty conclusively that archeocyathids were an early experiment in the Phylum Porifera--they are now generally considered an
extinct type of calcareous sponge. Archaeocyathids were sessile, marine organisms of shallow, tropical and subtropical waters
that lived during the early Cambrian period about 550 million years ago. They were widespread in Cambrian seas throughout
the world and were the first major reef-builders before the true corals
PHYLUM PORIFERA (sponges)
Porifera means "pore-bearing". Exterior covered by tiny pores.
Chief characteristics: Globular, cylindrical, conical or irregular shape. Interior may be hollow or filled with branching canals.
Solitary or colonial. Skeletal elements are called spicules, and they may be separate or joined. Composition may be calcareous,
siliceous or organic material called spongin. Geologic range: Cambrian to Recent.
Mode of life: Attached to the sea floor. Most are marine.
Sponges have an asymmetric body with no true tissues, or organs. They have two layers of cells. Flattened cells cover the
exterior. Collar cells line the interior chambers. Collar cells move large volumes of water through body pores by their beating
flagella. They also trap suspended food particles in their microvilli collars. Between the two layers of cells there is a semifluid
matrix with needlelike structures for support. Sponges reproduce sexually and have a free-living larval stage. They also
reproduce asexually by fragmentation or gemmules.
CONULARIDS- Although there is some controversy in regards to the systematic position of the conularids, most workers
today place them with the scyphozoan cnidarians. The exoskeleton of conularids is composed of chitin and in outline is
pyramidal with four sides. The exterior surfaces of conularids normally have finely spaced longitudinal ribs. The interior of
conularids may have thickenings or septa developed. In life, conularids lived attached apical end down to the substrate.
Conulariids have been the subject of speculation for a century and a half. They aren't that uncommon; there are a number of
genera, and they ranged from the Middle Ordovician to the Triassic. There are even a few cases in which conulariid soft parts
have been preserved. Nonetheless, exactly what they were is still not settled. Because of their fourfold symmetry, they have
often been placed in the Cnidaria by analogy with the fourfold Scyphozoa. However, their skeleton was very different from
anything known in the Cnidaria, and they may represent a separate, extinct phylum, probably triploblastic