Ediacaran Cloudina Fossil

Description: The Cloudinids lived during the late Ediacaran, and became extinct at the base of the Cambrian. They are one of the earliest of what is termed the Small Shelly Fauna (SSF) to emerge in the geological record. They consisted of nested calcareous cones that were thought to have been a defense measure against predation. Indeed some have been found with holes drilled in the shelss, the result of some unknown predator.

The classification of these enigmatic animals is uncertain.; they have been variously looked upon as polychaete worms and as cnidarians. Their lifestyle is equally mysterious. They have been thought to have shared a home with the stromatolites, adding additional shells as the microbial mat grew. Since none have been found embedded in a mat, this interpretation is open to question. One specimen has been etched with acid to show the shell detail while the other has been polished to show the shells in a more natural state.

Cloudina fossils often have show borings that are thought to have been made by predators. In addition, the distribution of borings in Cloudina suggests selection for size – the largest holes appear in the largest shells. This evidence of selective attacks by predators suggests that new species may have arisen in response to predation, which is often presented as a one potential cause among many of the rapid diversification of animals in the Cambrian Explosion.

* Hahn, G., and H. D. Pflug (1985). "Die Cloudinidae n. fam., Kalk-Röhren aus dem Vendium und Unter-Kambrium". Senckenbergiana lethaea 65: 413–431.