Plated Cambrian bilaterians reveal the earliest stages of echinoderm evolution

Samuel Zamora, Imran A. Rahman, Andrew B. Smith

Research output: Contribution to journalArticle (Academic Journal)peer-review

41 Citations (Scopus)
365 Downloads (Pure)

Abstract

Echinoderms are unique in being pentaradiate, having diverged from the ancestral bilaterian body plan more radically than any other animal phylum. This transformation arises during ontogeny, as echinoderm larvae are initially bilateral, then pass through an asymmetric phase, before giving rise to the pentaradiate adult. Many fossil echinoderms are radial and a few are asymmetric, but until now none have been described that show the original bilaterian stage in echinoderm evolution. Here we report new fossils from the early middle Cambrian of southern Europe that are the first echinoderms with a fully bilaterian body plan as adults. Morphologically they are intermediate between two of the most basal classes, the Ctenocystoidea and Cincta. This provides a root for all echinoderms and confirms that the earliest members were deposit feeders not suspension feeders.

Original languageEnglish
Article numbere38296
Number of pages11
JournalPLoS ONE
Volume7
Issue number6
DOIs
Publication statusPublished - 6 Jun 2012

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