HistGeolChapt13 - Chapter 13 Paleozoic Vertebrates...

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Unformatted text preview: Chapter 13 Paleozoic Vertebrates & Plants From the Sea to the Land, the development of Vertebrates, Insects, and Plants. First evidence of Chordates , organisms with a notochord, a dorsal hollow nerve cord,and gill slits Early Cambrian - Found in 525 m.y. old rocks in Yunnan province, China Chengjiang Fauna. (See slide 3). Also Pikaia Burgess Shale Fauna British Columbia. Earliest fish remains are found in Late Cambrian rocks. All known Cambrian and Ordovician fossil fish have been found in shallow nearshore marine deposits. Yunnanozoon lividum is one of the oldest known chordates Found in 525 Myr old rocks in Yunnan province, China 5 cm (2 inches) long A fragment of a plate from Anatolepis (A primitive member of the class Agnatha (jawless fish)) , one of the oldest known fish from the Late Cambrian Deadwood Fm. of Wyoming. The oldest fossil remains of nonmarine fish are from the Silurian Period, evidence that fish originated in the oceans. The oldest and most primitive of the class Agnatha are the ostracoderms (bony skin). These are armored jawless fish that first evolved during the Late Cambrian reached their zenith during the Silurian and Devonian and then became extinct. The majority of ostracoderms lived on the seafloor, probably browsing through the bottom sediment for small bits of food. Geologic Ranges of Major Fish Groups an ostracoderm ( Hemicyclaspis ) a placoderm ( Bothriolepis ) an acanthodian ( Parexus ) a ray-finned fish ( Cheirolepis ) The Devonian Period - the Age of the Fish, all major fish groups present during this time. The evolution of jaws was a major evolutionary advantage among primitive vertebrates. Jawless ancestors could only feed on detritus, jawed fish could chew food and become active predators opening new ecological niches. The vertebrate jaw is an excellent example of evolutionary opportunism Movable jaw evolution of the first three gill arches. Movable jaw may have likely initially provided for more oxygen movement through gills. First jawed fish Early Silurian rocks belong to the acanthodians , a group of enigmatic fish charac- terized by large spines, scales covering much of the body, jaws, teeth, and reduced body armor. May have included ancestors of bony and cartilaginous fish groups. The acanthodians were most abundant...
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HistGeolChapt13 - Chapter 13 Paleozoic Vertebrates...

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