Cyclomedusa

Cyclomedusa is an ancient circular fossil with a circular bump in the middle and as many as 5 circular growth ridges around it. Many specimens are small but specimens in excess of 20cm are known. The concentric disks are not necessarily circular especially when adjacent individuals interfere with each other's growth. Many radial segment lines -- somewhat pineapple like -- extend across the outer disks. A few specimens show what might be a stem extending from the center in some direction or other.

Cyclomedusa was originally thought to be jellyfish, but some specimens seem to be distorted to accommodate adjacent specimens on the substrate probably indicating a creature living on the bottom. The markings do not match the musculature pattern of modern Jellyfish. It has been conjectured to be a holdfast for some stalked form -- possibly an octacoral -- or possibly something else entirely. The animal is widely distributed with a number of species described. It is possible that they represent different modes of preservation for one animal, that many species exist, or that several different animals have been grouped together under one name.

Cyclomedusa is known from neoproterozoic beds in Ediacara (Australia), Finnmark(Norway), Charnwood Forest (England), Olenek (Russia), North China, Newfoundland, Northwest Canada, Podolia (Ukraine), The Ural Mountains (Russia), The White Sea (Russia), and Sonora (Mexico). It is regarded as a member of the Vendazoa -- a group of somewhat obscure animals that thrived just before most of the modern multicellular animal phyla appeared. It is unclear if the Vendazoa are plants, animals, or something else entirely. Cyclomedusa has no known relatives.

External Link

• A picture of Cyclomedusa can be found at http://www.btinternet.com/~vendian/FOSSILWEB/vendian.htm