Life of the Paleozoic CHAPTER 10
Paleozoic Organism Innovations • Shelly fauna • Land plants • Amniotes • Vertebrates
Precambrian Life Precambrian life begins as: • Prokaryotes (beginning at least 3.5 bya, possibly 3.8 bya or more, in the Archean) • Archaea (including thermophiles of deep sea hydrothermal springs) • Bacteria (some of which were anaerobic) • Photosynthetic cyanobacteria which constructed filamentous algal mats (stromatolites), sometimes called blue-green algae.
Precambrian Life (continued) • Eukaryotes (beginning about 1.4 -1.6 bya in the Mesoproterozoic) • Microscopic unicellular organisms of various types (Protozoa) • Acritarchs - probably phytoplankton • Algae • Metazoans or multicellular organisms (beginning in the Neoproterozoic) • Soft-bodied Ediacaran fauna (beginning about 630 mya or 0.63 bya) • Small shelly fossils - tubes etc., few mm in size, possibly the remains of primitive molluscs, worms, & sponges.
Modes of Life in Marine Zone(pg. 130-132) • Location: nektonic, planktonic, benthic • Bottom dwellers: epifaunal, infaunal, mobile • Feeding strategy: filter-feeders, sediment-feeders
Marine Ecosystem • Where and how animals and plants live in the marine ecosystem
Animals with shells • Pre-Shells: Proterozoic (Ediacaran) Fossils • Tommotian Fauna Fossils from Siberia, Sweden, N. America, Antarctica, and England • Shells and elements of tiny mollusks, sponges, and cap-shaped tubular shells (calcium carbonate or phosphate) • Anabarites: tubular fossils (three tubes joined together) • Lapworthella: cap-shaped and ornamented
Late Precambrian and Early Cambrian shell-bearing fossils from Siberia.(A) Anabarella, a gastropod; (B) Camenella, affinity uncertain; (C) Aldanella, a gastropod; (D) sponge spicule; (E) Fomitchella, affinity uncertain; and (F) Lapworbella. (After Matthews, S. J., and Missarzbevsky, V. V. J. 1975. Geol. Soc. London 131: 289-304.)
Lagerstätten!! • Extraordinary Early Cambrian Soft-Body Fossil Sites • Burgess Shale, British Columbia, Canada (525 m.y. old) • viewed as one of the most important faunas in fossil record • impressions and films on bedding planes • limited exposure near Mt. Wapta, BC • discovered by C.D. Walcott in 1909 • Chengjiang site, China (535 m.y. old) • 10 m.y. older than Burgess Shale • Early chordates
Figure 10-2 (p. 332) Geologic time scale across the Proterozooic-Cambrian boundary showing position of the Ediacaran, Chengjiang, and Burgess Shale faunas.
Burgess Shale Fauna • Several groups of arthropods, including trilobites and crustaceans • Sponges • Onycophorans • Crinoids • Molluscs • Three phyla of worms • Chordates (Pikaia) • Many other species, some of which cannot be placed into known phyla
Burgess Shale Fauna Pikaia, one of the oldest known Chordates. The giant predator of the Cambrian seas, Anomalocaris, up to 60 cm long. Hallucigenia-- Which way is up?
Invertebrates of the Paleozoic • Unicellular Groups (Protistans) • Cup Animals: archaeocyathids • Pore-Bearers: porifera (sponges) • Corals and Other Cnidarians • Bryozoans (“Moss Animals”) • Brachiopods (most abundant & diverse Paleozoic fossil) • Mollusks • Arthropods • Echinoderms (Spiny-skinned)
Protists of the Paleozoic • While not members of Kingdom Animalia, they are animal-like (non-photosynthetic) single-celled organisms with shells or hard parts living during the Paleozoic. • Both the Foraminifera and the Radiolaria belong to Phylum Sarcodina.
Cup Animals: archaeocyathids • Conical or vase-shaped skeletons • Extinct phylum by end of Cambrian • Earliest reef builders • N. America, Siberia, Antarctica, Australia • Australian reefs: 60 m x 200 km
The archaeocyathan skeleton. (A) Longitudinally fluted cup of an archaeocyathan, about 6 centimeters in height. (B) Transverse section of a nonfluted archaeocyathan having closely spaced parieties and a vesicular inner wall (maximum diameter is 4 centimeters).
Pore-Bearers: porifera (sponges) • Sessile, bottom dwellers • Spicules--found commonly in sediment record • Stromatoporoid
Corals and Other Cnidarians • Main groups • sea anemones • sea fans • jellyfish • Hydra • reef-forming corals
Corals • Body form: polyp or medusa • Anthozoa (stony corals): polyp secrets Calcium carbonate cup and lives within it • theca (cup) divided by vertical plates (septa) • tabulae (horizontal growth plates in theca)
Figure 10-22 (p. 341)Comparison of polyp and medusa forms in cnidarians.
Rugose versus tabulate corals • Rugose: have septa at four locations • Tabulate: corals have obscure septa, tabulae are dominant (e.g., honeycomb and chain corals)
Rugose versus tabulate corals Tabulate Rugose
Bryozoans (Moss Animals) • Minute, symmetrical, colonial, “twig-like” macroscopic appearance • Zooid = individual fossil living site • Zooecium = capsule which contains zoids • Range: Lower Ordovician to present • Paleozoic forms: common in reefs • Encrusting or arborescent • Branching zooarium • Star-shaped patterns • Corkscrew: fenestellid colony, Archimedes • Fan-Shaped
Bryozoans Fenestrella, a lacy bryozoan from the Devonian Specimen of the fossil bryozoan, Archimedes
Brachiopods (most abundant, diverse, and useful Paleozoic fossil group) • Bivalves symmetrical across the valve (shell); valves are dorsal and ventral • Calcium carbonate (most taxa), chitin, calcium phosphate • Articulate brachipods: valves hinged along posterior margin (teeth and sockets); commonly ribbed or ornamented • first occurred during Cambrian • flourished during Ordovician • common during Late Paleozoic • persist today • Inarticulate brachiopods: valves held by muscles • commonly chitino-phosphatic • simple spoon-shaped or circular valves • major decline in diversity during Ordovician; exist today
Living positions of articulate and inarticulate brachiopods. (A) The articulate (B) Interior of brachial valve showing ciliated lophophore. (C) The inarticulate brachiopod lives in a tube
Articulate Brachiopods Ordovician strophomenid articulate brachiopod, Rafinesquina Miscellaneous Paleozoic articulate brachiopods.
Phylum Mollusca • Clams, oysters, snails, slugs, Nautilus, squid, octopus, cuttlefish • Mollusca means " soft bodied" . • Chief characteristics: Soft body enclosed within a calcium carbonate shell. Muscular part of body of clams and snails and some other groups of molluscs is called the foot. • Geologic range: Cambrian to Recent. • Mode of life: Marine, freshwater, or terrestrial. Some swim, some float or drift, some burrow into mud or sand, some bore into wood or rock, some attach themselves to rocks, and some crawl.
Figure 10-31 (p. 347) Some common members of the phylum Mollusca.(From Levin, H. L., 1975. Life Through Time. Dubuque, IA: William C. Brown Co.)
Class Bivalvia (Pelecypoda) • Includes: Clams, oysters, scallops, mussels • Name: Bivalvia means " two" (bi) + " shells" (valvia). • Chief characteristics: Skeleton consists of two calcareous valves connected by a hinge. Bilateral symmetry; valves are same • Geologic range: Early Cambrian to Recent • Mode of life: Marine and freshwater. Many species are infaunal burrowers or borers, and others are epifaunal
Class Gastropoda • Includes: Snails and slugs • Name: Gastropod means "stomach" (gastro) + "foot" (pod). • Chief characteristics: Asymmetrical, spiral-coiled calcareous shell. • Geologic range: Early Cambrian to Recent. • Mode of life: Marine, freshwater or terestrial.
Gastropods Fossil gastropod Modern gastropod
Class Cephalopoda • Includes: Squid, octopus, Nautilus, cuttlefish • Name: Cephalopod means " head" (kephale) + " foot" (pod). • Chief characteristics: Symmetrical cone-shaped shell with internal partitions called septae (singular = septum). Shell may be straight or coiled in a spiral which lies in a plane. Smooth or contorted sutures visible on the outside of some fossils mark the place where septae join the outer shell. • Geologic range: Late Cambrian to Recent. • Mode of life: Marine only; carnivorous (meat-eating) swimmers.
Nautiloids and Ammonoids Diagram of a nautiloid cephalopod illustrating suture pattern. Diagram illustrating ammonite sutures in an ammonoid. Nautilus. Ammonite cephalopod.