Thursday 7th June
Neil Chalmers Seminar Room, DC2, 16:00
Form and function in Cambrian stem-group echinoderms
Dr Imran Rahman, School of Geography, Earth & Environmental Sciences, University of Birmingham
Modern echinoderms such as sea urchins and starfish are characterized by a unique pentaradiate body plan, which is established during ontogeny and clearly distinguishes them from other bilaterians. By contrast, some of the earliest fossil representatives of the phylum do not display radial symmetry; most strikingly, two Cambrian groups, ctenocystoids and cinctans, lack almost all the derived characters shared by extant species. These taxa are best interpreted as basal stem-group echinoderms, and hence may provide important insights into the origin and early evolution of echinoderms. However, their fossils are often difficult to interpret because so little of their anatomy has been deciphered, with competing phylogenetic hypotheses derived from differing interpretations of enigmatic characters. In order to better understand the evolutionary significance of these aberrant echinoderms, complete, three-dimensionally preserved ctenocystoid and cinctan fossils were studied using novel imaging (X-ray micro-tomography) and computer modelling (computational fluid dynamics) techniques. The results allow us to reconstruct form and function in the echinoderm stem-group, with implications for the assembly of the echinoderm body plan.
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