Vertebrates - Vertebrates The class Chondrichthyes contains...

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Vertebrates The class Chondrichthyes contains approximately 850 species of skates, rays, and sharks. They have jaws, lots of teeth, paired fins, and a cartilage endoskeleton. Cartilaginous fish first appeared during the Devonian period and expanded in diversity during the Carboniferous and Permian before nearly disappearing during the great extinction that occurred near the end of the Permian. Some fragmentary evidence suggests cartilaginous fish were present during the Ordovician, although the best skeletal evidence is from the Devonian. Despite scanty skeletal presence (cartilage not preserving nearly so well as bone), shark teeth are common fossils in some deposits. The crossopterygian fish (represented by the marine extant deep-living coelacanth and extinct freshwater forms) are regarded as ancestors of early amphibians. Extinct crossopterygians had strong fins, lungs, and a streamlined body capable of swimming as well as traveling short distances out of water. Plants
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Vertebrates - Vertebrates The class Chondrichthyes contains...

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