Palaeocast

Echinoderms are characterised by a mineralised skeleton, specialised water vascular system and five-fold symmetry. It is this unusual body plane symmetry that gives the starfish its star-shape. None of these features, however, are possessed by the closest living relatives of echinoderms – the hemichordates. Palaeontology offers a unique perspective into the early evolution of echinoderms, revealing that echinoderm characteristics were acquired in a step-wise fashion from a bilaterally symmetrical ancestor. We speak to Dr Imran Rahman, a postdoctoral researcher at the University of Bristol, about the early evolution of echinoderms, from worms to stars.