Earliest known echinoderm — a new Ediacaran fossil from the Pound Subgroup of South Australia

Arkarua adami gen. et sp. nov., a small disc-like animal with a pentameral arrangement of grooves on its oral surface, is preserved as an external mould on the base of sandstone beds within the Ediacaran (Late Precambrian) Ediacara Member of the Pound Subgroup, in the Flinders Ranges. While the limitations of preservation do not allow identification of some important organs, the pentameral symmetry and resemblance to Early Cambrian edrioasteroids enable the recognition of Arkarua as the earliest known echinoderm.