THE ANTILLEAN TERTIARY CRINOID FAUNA

Abstract

Fossil crinoids are described from the Lesser Antilles for the first time. Crinoids are now known to occur in the Miocene of Carriacou, the Grenadines (four species), and in the Eocene and Miocene of Barbados (three species). Taxa include: isocrinid sp. indet., hyocrinid sp. indet. (both Eocene); the isocrinids Neocrinus decorus (Wyville Thomson, 1864) and Isocrinus sp., the bourgueticrinid Democrinus? sp., and the comatulid Horaeometra sp. (all Miocene). Despite the preponderance of taxa in open nomenclature, these are among the very few records of fossil crinoids from the Antillean region. Faunas are dominated by the columnals of isocrinids; bourgueticrinid and millericrinid columnals, and comatulid centrodorsals, are very rare, despite comatulids being both the most diverse crinoids in the modern fauna and the only group that occurs in shallow-water environments. Post-Eocene crinoid faunas in the Antillean region include taxa that are similar, at least at the generic level, to those of the present day. Democrinus? sp. from Carriacou is the first pre-Quaternary bourgueticrinid from the Antilles. Horaeometra sp. is the first fossil comatulid from the Antilles to be classified to generic level.The extant crinoid fauna of the tropical western Atlantic includes 23 genera/34 species of “stalkless” comatulid crinoids and eight genera/ten species of stalked crinoids. This is far greater than the known diversity of fossil crinoids from the Antillean region, which spans circa 120 Ma. The apparent rarity of fossil crinoids is probably part artefact, produced by collection bias, taphonomic effects, and the relative rarity of exposures of sedimentary units deposited in 150+ m, i.e., the environment of extant stalked crinoids.