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The Precambrian - (650 to 544 million years ago and is...

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The Precambrian The first protist (eukaryotic) fossils have commonly been thought to be in rocks approximately 1.2-1.4 billion years old (Proterozoic) from the Bitter Springs Formation in Australia. The Bitter Springs deposits also yield a variety of bacteria and cyanobacterial types. Recent study of the Bitter Springs eukaryote fossils suggests they may in fact be cyanobactria. A group of undoubted eukaryote fossils is the "acritarchs". This term applies to resting cycts of single-celled algae. Acrtitarchs have been recovered from sediments that are as old as 1.8 billion years. 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
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Unformatted text preview: (650 to 544 million years ago), and is characterized by the appearance of soft-bodied animal fossils. Multicellular animal fossils and burrows (presumably made by unknown multicellular animals) first appear 700 million years ago, during the late precambrian 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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