Death assemblage : become fossils at a site away from their actual habitat due to death and transport to an area. Life assemblage : organisms preserved in their natural habitat. Obvious example: If large mammal bones were found scattered among fossil fish, one presumably would not invoke the existence of primitive mammals that walked on lake or ocean floors! Environments: fossils are generally restricted to areas of deposition. Upland areas less likely to preserve fossils: more erosion. In deserts material is covered by sand and has a good chance of being fossilized. In shallow seas sediment is being deposited and can cover skeletons. Some of the best fossil assemblages are from shallow sea deposits, lake beds, outwash plains from periodic river floodings, etc. Ediacara fauna (640 MyBP) Many forms that bear some resemblance to modern phyla. Appears as if it were a major "evolutionary experiment" that did not work as it appears that none of their representatives made it into the Cambrian. Burgess shale
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Cambrian, Charles Doolittle Walcott, Burgess Shale, shallow seas sediment