Australia: The Land Where Time Began

A biography of the Australian continent 

Spiral-Plated Echinoderms from Gondwana in the Cambrian Reveal the Earliest Pentaradial Body Plan

Echinoderms are the only organisms among the animal phyla that have a pentaradial body plan and critical data on the origin of this novel organisation is provided by their fossil record as it reveals intermediate stages. In this paper the authors report on a spiral-plated animal of Early Cambrian age recovered from Morocco that is the most primitive pentaradial echinoderm discovered so far, being intermediate between helicoplacoids, a bizarre group of echinoderms with a spiral body plan, and crown-group pentaradiate echinoderms. The common pattern that underpins the body plans of the major echinoderm clades, pelmetazoans and eleutherozoans, is revealed by this fossil, which fills an important gap, showing that differential growth played an important role in their divergence. It also adds to the remarkable disparity of body plans that appeared at the time of the Cambrian Explosion.

Sources and further reading

1. Smith, Andrew B., and Samuel Zamora. "Cambrian Spiral-Plated Echinoderms from Gondwana Reveal the Earliest Pentaradial Body Plan." Proceedings of the Royal Society B: Biological Sciences 280, no. 1765 (August 22, 2013 2013).