Enigmatic Ediacaran Putative Cnidarian Fossils

They bear a striking resemblance to the extant pelagic cnidarian hydroid porpita porpita (or blue button), and I'll go with that associated taxonomy above, or just use enigmatica. The animal fossil record from the ediacaran is sparse, especially because animals had yet to evolved hard shells. The blue button lives on the surface of the sea and consists of two main parts: the float and the hydroid colony. The hard golden-brown float is round, almost flat, and about one inch wide. The hydroid colony, which can range from bright blue turquoise to yellow, resembles tentacles like those of the jellyfish.

The Ediacaran biota include the oldest definite multicellular organisms with tissues, and the most common types resemble segmented worms, fronds, disks, or immobile bags. They bear little resemblance to modern lifeforms, and their relationship even with the later life forms of the Cambrian explosion is difficult to interpret. The evolutionary divergence of cnidarian and bilaterian lineages from their remote metazoan ancestor occurred at an unknown depth in time before the Cambrian, since crown group representatives of each are found in Lower Cambrian fossil assemblages. The multicellular cnidarians evolved early on earth and despite their primitive nature have endured for hundreds of million of years since. It remains uncertain whether bilaterians evolved from early cnidarians or from the hypothesized triploblastic ancestors of cnidarians.

These fossils are very rare and have been legally collected and exported.

• Also see:
  Ellis L. Yochelson and Charles E. Mason. 1986. A Chondrophorine Coelenterate from the Borden Formation (Lower Mississippian) of Kentucky, Journal of Paleontology, Vol. 60, No. 5 (Sep., 1986), pp. 1025-1028
• Chen, J.-Y., Oliveri, P., Gao, F., Dornbos, S.Q., Li, C-W., Bottjer, D.J. and Davidson, E.H. (August 2002). "Precambrian Animal Life: Probable Developmental and Adult Cnidarian Forms from Southwest China" (PDF). Developmental Biology 248 (1): 182–196.