Arkarua
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| Arkarua Temporal range: Ediacaran
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| Genus: | Arkarua
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| Species: | A. adami
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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.
Arkarua is known only from the Ediacaran beds of the Flinders Ranges in South Australia. The generic name refers to Arkaru, a mythical giant snake of the local Aboriginal people.[1]
Classification
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.[citation needed]
This identification remains suspect, as the fossils do not appear to have either madreporites, or plates of stereom, a unique crystalline form of calcium carbonate from which echinoderm skeletons are built. These two features are diagnostic of all other echinoderms, as all extinct and extant echinoderms have either one, the other, or both features present.[2]
See also
References
- ^ 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
- McMenamin M. (1986). The Garden of Ediacara (PDF). ISBN 978-0-231-10559-0. Retrieved 2007-03-08.
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External links
- Vendian animals: Arkarua from the Ediacara Hills of Australia, from the University of California Berkeley Museum of Paleontology. (pictures)