Definition of Aysheaia
: a genus of soft-bodied marine invertebrates known from fossils of the Cambrian period that are thought to be ancestral to the velvet worms (phylum Onychophora) A marine onychophoran from the Cambrian would be a creature of supreme evolutionary importance—and Aysheaia, generally so interpreted, became a hero of the Burgess. — Stephen Jay Gould, Wonderful Life: The Burgess Shale and the Nature of History, 1989
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