Nimbia
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Nimbia occlusa is a form of Ediacaran fossil shaped like a circular or oval disk. It has a thick rim around the margin. Within the rim the fossil is usually flat, but may have a central nipple or dimple. These fossils are generally believed to be those of cnidarians. Their size goes up to 6 cm in diameter, with the rim being 1 cm thick. Some fossils are distorted, indicating that the original animal was flexible. The interpretation is that the fossil is a pedestal or possibly a sand ballast that weighed the organism down.
Nimbia occurs in numerous locations across a large range of time. This suggests that several different organisms may be making these fossils. It occurs in the Twitya formation in the Mackenzie Mountains in Canada dated at 610 mya predating the Varangian glaciation. This may predate the Ediacaran period, and come from the Cryogenian period. In this deposit Nimbia is the only animal-like fossil, and so is probably the earliest fossil of any animal. Aspidella is also claimed from this area. Morania and Beltina carbonaceous film fossils in the Twitya formation are not considered to be animals. Nimbia-like fossils have also been found in the Cambrian period, showing that it was a survivor of the mass extinction at the end of the Precambrian.
Nimbia was named by Mikhail Fedonkin in 1980.
[edit] References
- Fedonkin MA. Novye Predstaviteli Dokembriyskikh Kishechnopolostnykh na Severe Russkoy Platformy (New Precambrian Coelenterata in the North of the Russian Platform). Paleontologicheskiy Zhurnal 2: 7-15. (1980)
