A starfish bed in the Middle Miocene Grand Bay Formation of Carriacou, The Grenadines (West Indies)

Abstract

The first starfish bed to be recognized from the Antilles is a lensoid body in the middle Miocene Grand Bay Formation of Carriacou, The Grenadines (West Indies). This unit was deposited in a turbidite basin in a region of active volcanism fed from one centre and preserves common deep-water taxa more typical of the Palaeozoic, such as crinoids and brachiopods. The starfish bed is a channel-fill deposit laid down in at least 150–200 m water depth, although the specimens may have been derived from shallower water. A goniasterid asteroid and an ophiacanthid ophiuroid have been recognized. The first articulated asteroid from the Antillean fossil record is Paragonaster(?) haldixoni sp. nov. In all skeletal features it appears close to the extant Atlantic species Paragonaster grandis H. L. Clark and P. subtilis (Perrier), but differs in having a single row of rectangular abactinal ossicles extending to the arm tip; these are longer than wide. The brittlestar, Ophiocamax ventosa sp. nov., is described on the basis of a fragmentary disc and arms from this deposit. The closest similarities are with the extant tropical western Atlantic species Ophiocamax hystrix Lyman and O. austera Verrill. However, the new species has thorns covering the entire surface of dorsal arm plates, while arm spines have a multitude of small thorns, loosely arranged in numerous rows and dorsal arm plate shape differs markedly. The occurrence of O. ventosa sp. nov. suggests that Ophiocamax has been a deep-sea taxon at least since the Miocene.