Arkarua

Taxobox
fossil_range = Ediacaran
regnum = "incertae sedis"
name = Arkarua
genus = "Arkarua"
species = "A. adami"

"Arkarua" 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. The only known species, "Arkarua adami", is 3 to 10 mm in diameter."Arkarua" is known only from the Ediacaran beds of the Flinders Ranges in South Australia, and takes its name from a mythical giant snake of the local Aboriginal people (Gehling 1987).

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, some claim that it can be further classified into the Edrioasteroidea, a subgroup of the echinoderms.fact|date=June 2007

However, it lacked a feature present in later echinoderms: the stereom, a unique crystalline form of calcium carbonate from which their skeletons are built.

External links

* [http://www.ucmp.berkeley.edu/vendian/arkarua.html Vendian animals: "Arkarua" from the Ediacara Hills of Australia] , from the University of California Berkeley Museum of Paleontology. (pictures)
* Gehling, J.G. 1987. Earliest known echinoderm — a new Ediacaran fossil from the Pound Subgroup of South Australia. Alcheringa 11:337-345.
* cite book
author = McMenamin M.
coauthors =
year = 1986
title = The Garden of Ediacara
volume =
isbn=9780231105590
url=http://www.earthscape.org/r3/mcm02/mcm02k.pdf
accessdate = 2007-03-08