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Temporal range: Ediacaran
Arkarua adami is a small, Precambrian disk-like fossil with a raised center, a number of radial ridges on the rim, and a five-pointed central depression marked with radial lines of 5 small dots from the middle of the disk center. Fossils range from 3 to 10 mm in diameter.
All known specimens of Arkarua are casts that give no clue to the internal structure, making classification problematic. Because of Arkarua's pentamerous symmetry, it is tentatively placed within phylum Echinodermata. Because of its flattened disk- or button-shape, coupled with its pentamerous symmetry, some claim that it can be further classified into the Edrioasteroidea, a class of the echinoderms.
- Gehling, J.G. 1987. Earliest known echinoderm — a new Ediacaran fossil from the Pound Subgroup of South Australia. Alcheringa 11:337-345.
- Paul D. Taylor, David N. Lewis Fossil Invertebrates Harvard University Press, 2007 ISBN 0-674-02574-1 pages 163-164
- Vendian animals: Arkarua from the Ediacara Hills of Australia, from the University of California Berkeley Museum of Paleontology. (pictures)