NEW CRINOIDS (ECHINODERMATA) FROM THE LLANDOVERY (LOWER SILURIAN) OF THE BRITISH ISLES

Abstract:  British Llandovery crinoids remain poorly known. Three species are documented herein that were originally described, but not published, by W. H. C. Ramsbottom. Clematocrinus ramsbottomi Fearnhead sp. nov. (Tortworth Inlier, Gloucestershire; Telychian) has a heteromorphic column, N434243414342434, radices directed away from the crown, and ten long, uniserial arms with a pustular aboral sculpture and long, slender pinnules. Clematocrinus spp. are widely distributed in the Silurian of England. Ptychocrinus mullochillensis Fearnhead and Donovan sp. nov. (Girvan district, Strathclyde; Rhuddanian) is the second report of this Upper Ordovician–Lower Silurian genus from outside North America. Although incompletely known, this species is distinguished by its hidden infrabasals, 20 arms and sunken interbrachial plates with a strongly stellate sculpture. Petalocrinus bifidus (Bather MS) Donovan and Fearnhead sp. nov. (Woolhope Inlier, Herefordshire; Telychian) is locally common enough to give its name to a mappable lithostratigraphic unit, the Petalocrinus Limestone. Unlike other Petalocrinus species known from the Silurian of China, northern Europe and North America, the fused arms of P. bifidus are divided in two by a proximal adoral ridge and an associated distal notch. Unlike extant crinoids, Petalocrinus probably lived as a rheophobe; the fused arms may have acted to deter predators.