Australia: The Land Where Time Began

A biography of the Australian continent 

Cambrian Explosion Fossils – “Radiate” Metazoan Body Plans

The fossil record of Radiata (Cnidaria and Ctenophora) is equivocal prior to the Cambrian; though it is suggested by molecular clock evidence that the phyla comprising Radiata branched from sponges about 780 Ma. In the latest Ediacaran there are a number of organisms of probable diploblastic grade that are known. Among the Cambrian SSFs there are a number of tube-like forms, such as anabaritids, protoconularids, as well as others from Stage 1 of the Cambrian that have collectively been called cnidariomorphs (Kouchinsky et al., 2012). As with the spicule gap there is a “Radiata gap”, that is less severe but just as troubling, between the probable clade origin and the first known fossil representatives. As usual, small body size and lack of hard parts imposes hurdles that may be sufficient to account for much of the gap.

Sources & Further reading

1. Erwin, Douglas H., & Valentine, James W., 2013, The Cambrian Explosion: The Construction of Animal Biodiversity, Roberts & Co., Greenwood Village, Colorado