Australia: The Land Where Time Began

A biography of the Australian continent 

Cambrian Explosion - Palaeoscolecidae

The Palaeoscolecidae is a group extinct forms of uncertain affinity that had thick bodies that were worm-like and were covered with calcium phosphate cuticular sclerites. The group has been interpreted as being peseudocoelomic and it is believed they likely had ecdysozoan affinities: they have been considered to be likely stem priapulids (T.H.P. Harvey, Dong & Donoghue, 2010), whereas it has also been proposed that they are stem Cycloneuralia (Conway Morris & Peel, 2010). In the Cambrian Stage 3 there is a diversity of mineralised sclerites of palaeoscolecids, and in the Sirius Passet and Chengjiang biotas body fossils have been recovered. Among extant pseudocoelomates most of the worm-like forms are about the correct size to be responsible for the small burrows and trails that have been recorded from the Neoproterozoic. The authors¹ suggest a better idea of which, if any, of the ecdysozoans crown groups were likely to have been present in the fauna of the Neoproterozoic when the phylogenies of these groups have been sorted out definitively.

Sources & Further reading

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