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

John W M Jagt,David A T Harper,Stephen K Donovan,Ron K Pickerill,Sabine Stöhr,Trevor A Jackson,William Lindsay,Ben Thuy,Roger W Portell

doi:10.1017/s0016756813000204

Abstract

AbstractThe 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.

Highlights

Until recently, the fossil record of asterozoans in the Antillean region consisted solely of disarticulated plates or ossicles (Donovan, 2001), unlike certain adjacent regions where well-documented complete specimens are locally common (e.g. Jones & Portell, 1988; Oyen & Portell, 2001; Blake & Portell, 2009, 2011)
Oral and adambulacral granulation and spination cannot be assessed, the present specimen would appear to be close to the genus Paragonaster, the rectangular abactinals of the single row that extends to the arm tip are longer than wide, rather than wider than long
In UF 114750, superomarginals at the arm base are first separated by a single row of rectangular abactinals from number 6; these are longer than wide

Summary

Introduction

The fossil record of asterozoans (asteroids or starfishes, and ophiuroids or brittle and basket stars) in the Antillean region consisted solely of disarticulated plates or ossicles (Donovan, 2001), unlike certain adjacent regions where well-documented complete specimens are locally common (e.g. Jones & Portell, 1988; Oyen & Portell, 2001; Blake & Portell, 2009, 2011). The fossil record of asterozoans (asteroids or starfishes, and ophiuroids or brittle and basket stars) in the Antillean region consisted solely of disarticulated plates or ossicles (Donovan, 2001), unlike certain adjacent regions where well-documented complete specimens are locally common Despite being diverse in the extant, shallow- and deep-water faunas (e.g. Hendler et al 1995 and Lyman, 1883, respectively), Antillean fossil asteroids and ophiuroids remain essentially unknown and have almost exclusively been recorded in open nomenclature, when noted at all. Its interpretation as a deep-water occurrence of asterozoans has important implications for our understanding of the taphonomy and evolution of Antillean echinoderms. From this deposit, new species of nominal fossil asteroid and ophiuroid are described. Donovan et al (1993) Donovan & Paul (1998) Berry (1935) present paper Donovan et al (2005) Vélez-Juarbe & Santos (2008) Dixon et al (1994) Vélez-Juarbe & Santos (2008)

History of research

Locality and horizon

Systematic palaeontology

Discussion