Cyclomedusa

Cyclomedusa is a genus of circular fossil from the Ediacaran biota, marked by a central bump surrounded by up to five concentric growth ridges and radial segment lines. First named by Reginald Sprigg in 1947 from Australian material, with the type species Cyclomedusa davidii, its fossils have since been found across Australia, Norway, England, Russia, China, Canada, Ukraine, Mexico and Brazil, ranging from a few centimeters to more than 20 centimeters across. Originally described as a jellyfish, most classifications now place it as an uncertain animal, if an animal at all, and some researchers argue it instead records a bottom dwelling microbial colony rather than a true organism.