The Rise of Animals
Source Institution: Smithsonian National Museum of Natural History
Source Exhibit: David H. Koch Hall of Fossils - Deep Time
Source Url: https://naturalhistory.si.edu/visit/virtual-tour/current-exhibits/deep-time-virtual-tour-fossil-list
Source Kind: interpretive_topic_or_panel
Use: research inspiration only; SAGE will write original interpretation
Dossier Status: scientifically_enriched_concept_room_02
Plain Language Explanation: Animals did not suddenly appear at the start of the Cambrian. Their evolutionary history reaches farther back into the Precambrian. By the Ediacaran Period, roughly 635 to 541 million years ago, seafloors supported a variety of large soft-bodied organisms. Molecular and comparative evidence suggests that some major animal lineages originated even earlier. The fossil record then becomes dramatically richer as animals develop new body plans, movement styles, feeding strategies and harder body structures.
Evidence: Ediacaran rocks preserve large soft-bodied organisms with distinctive body forms.; Trace fossils record movement and burrowing before and around the Ediacaran-Cambrian transition.; Molecular and developmental studies indicate divergence of some animal lineages before their abundant appearance in Cambrian fossil deposits.
Examples From Collection: Archaeocyathus sp.; Marpolia spissa; Waptia fieldensis; Wiwaxia corrugata
Common Misconception: The Cambrian explosion was not the literal creation of the first animal life in a single instant. Animals and their ancestors existed before the Cambrian.
What Scientists Still Debate: Researchers continue to debate the exact relationships of many Ediacaran organisms to later animal groups and the timing of the earliest branches in the animal tree.
Sources: https://naturalhistory.si.edu/education/teaching-resources/life-science/early-life-earth-animal-origins; https://profiles.si.edu/display/sro_108169; https://www.si.edu/newsdesk/factsheets/david-h-koch-hall-fossils-deep-time
Enrichment Method: SAGE original interpretive concept; Smithsonian-derived source title retained; Cambrian and Ordovician diversification separated; evidence distinguished from inference