The late Cretaceous crinoid Uintacrinus socialis Grinnell, which is a potential marker for the base of the Upper Santonian Substage, is reported from the Inoceramus Shales of St Ann's Great River Inlier on the north coast of Jamaica. This is the first record of this species from the Caribbean region and marks its lowest latitudinal distribution reported to date. The Inoceramus Shales are a deep-water clastic mudstone unit which extends the palaeoecological distribution of this crinoid. Uintacrinus socialis proves that the Inoceramus Shales are of Santonian age and will help constrain correlations between the shallow-water platform carbonate/volcaniclastic facies found in the arc successions of the Caribbean and the international chronostratigraphy.
