Paleozoic Life Ch 12 & 13 This artistic diorama models the living Environment for the Burgess shale organisms

Visible Life In the Cambrian system of rocks, a large number of visible complex species were observed. Life had been single-celled simple organisms for billions of years. The “sudden” appearance of large, well-preserved organisms caused scientists to use the term “Cambrian Explosion” Not so fast – the Cambrian period lasted for 54 million years. Life appeared to evolve more rapidly but there had been many steps Leading to the new life forms. The Ediacara fossils were multi-celled soft-bodied predecessors Increase in oxygen may be responsible for increase in body size. Ocean chemistry was evolving and may have increased in calcium. Cambrian continents were apart allowing more marine habitat. Sauk transgression created more shallow marine habitat on shore. Global warming was occurring.

Emergence of shelly fauna This Cambrian fossil is a few mm

What are advantages to having an exoskeleton? Protection from UV light, allowing organisms into shallow waters Prevents drying out in intertidal locations Supporting skeleton (shell) allows for increased size and attachment of muscle Protection from predators

Cambrian predator: anamalocoris

Olenellus, a Cambrian trilobite shows signs healing wounds

Marine ecosystem: plankton (phyto- zoo-), nekton, benthos, sessile, mobile, epifauna, infauna

Marine Ecosystem Where and how animals and plants live in the marine ecosystem Plankton: Jelly fish Sessile epiflora: seaweed Nekton: fish cephalopod Sessile epifauna: bivalve Benthos: d-k crinoid coral

Marine Ecosystem Mobile epifauna: gastropod, starfish Infauna: worm, bivalve

Marine Ecosystem Suspension feeders: coral crinoid bivalve

Marine Ecosystem worm sediment- deposit feeder Carnivores-scavengers: starfish Herbivores: gastropod

Trilobites: Conspicuous Cambrian fossils Figure 1 Cedaria minor, from the Cambrian Weeks Formation, Utah, illustrates the major body parts of a trilobite. Fig. 1, p. 248

Agnostus Believed to be blind Other trilobites have Compound eyes Figure 3 Hypagnostus parvifrons, a small agnostid trilobite from the Cambrian Marjum Formation, Utah. Fig. 3, p. 249

Figure 6 Schizochroal eyes from the trilobite Eophacops trapeziceps. Fig. 6, p. 249

Figure 5 Holochroal eyes from the trilobite Scutellum campaniferum. Fig. 5, p. 249

Middle Ordovician Figure 12.9: Middle Ordovician Marine Community. Reconstruction of a Middle Ordovician seafloor fauna. Cephalopods, crinoids, colonial corals, bryozoans, trilobites, and brachiopods are shown. Fig. 12-9, p. 251

Late Ordovician Figure 12.11: Representative Brachiopods and Graptolites. (a) Brachiopods are benthic, sessile, suspension feeders. Fig. 12-11a, p. 252

Figure 12.11: Representative Brachiopods and Graptolites. (b) Graptolites are planktonic suspension feeders. Shown is Phyllograptus angustifolius from Norway. Fig. 12-11b, p. 252

Figure 12.12: Conodonts and the Conodont Animal. (a) Conodonts are microscopic toothlike fossils. Cahabagnathus sweeti, Copenhagen Formation (Middle Ordovician), Monitor Range, Nevada (left); Scolopodus, sp., Shingle Limestone, Single Pass, Nevada (right). Fig. 12-12a, p. 253

Middle Devonian Reef Buildiers

Middle Devonian New York State Eurypterid Figure 12.14: Silurian Brackish Water Community. Restoration of a Silurian brackish water scene near Buffalo, New York. Shown are algae, eurypterids, gastropods, worms, and shrimp. Fig. 12-14, p. 254

Late Devonian Ammonoid Figure 12.15: Ammonoid Cephalopod. A Late Devonian-age ammonoid cephalopod from Erfoud, Morocco. The distinctive suture pattern, short stratigraphic range, and wide geographic distribution make ammonoids excellent guide fossils. Fig. 12-15, p. 254

Figure 12.16: Late Mississippian Marine Community. Reconstruction of marine life during the Mississippian, based on an Upper Mississippian fossil site at Crawfordville, Indiana. Invertebrate animals shown include crinoids, blastoids, lacy bryozoans, brachiopods, and small corals. Fig. 12-16, p. 255

Figure 12.19: Phanerozoic Marine Diversity. Phanerozoic diversity for marine invertebrate and vertebrate families. Note the three episodes of Paleozoic mass extinctions, with the greatest occurring at the end of the Permian Period. Fig. 12-19, p. 257

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