The morphology, ontogeny, and inferred behaviour of the deep-sea echinoidCalymne relicta(Holasteroida)

Abstract

The deep-sea holasteroid Calymne relicta was first described from a few fragments discovered by the HMS ‘Challenger’ in the Bermuda abyssal plain more than a century ago. In addition to re-examining the type material, we describe herein new specimens from unpublished material collected between 3720 and 4860 m during three scientific expeditions that took place on both sides of the North Atlantic between 1966 and 1991. The new material includes juvenile and adult specimens in sufficiently good preservational state to allow a full redescription, including all types of appendages, some of which have never been described. These new observations confirm the atypical characteristics of C. relicta, including test morphology and spines that have no equivalent in other extant taxa. We explore in detail characteristics of this species that were almost impossible to interpret previously.