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Evolution and Classification of Animals

Evolution and Classification of Animals - Evolution and...

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Evolution and Classification of Animals Multicellular protists appeared in the fossil record more than 600 million years ago near the very end of the precambrian. This time is referred to as the Vendian Period (650 to 544 million years ago), and is characterized by the appearance of soft-bodied animal fossils, some of which are shown in Figure 2. Multicellular animal fossils and burrows (presumably made by unknown, soft-bodied multicellular animals) first appear 700 million years ago, during the Vendian time. All known Proterozoic animal fossils had soft body parts: no shells or hard (and hence preservable as fossils) parts. There are some paleontologists who suspect that the Vendian faunas were reduced by an extinction event, possibly related to massive glaciation, at the close of the vendian time. In any event, many animals in the Vendian assemblages are quite unlike anything living today, while others can be traced to extant phyla.
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The Cambrian: Animals with Hard Body Parts
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