Sea Lilies of the Genus Bathycrinus (Crinoidea, Bathycrinidae) from the Yap and Palau Trenches

AbstractTwo species of the genus Bathycrinus were found in the Yap and Palau trenches. B. longicolumnalis n. sp. differs from other Bathycrinus species in having strongly bent lateral wings on the primibrachials and very elongate mesistele columnals. Ratio of length to diameter in the most elongate columnal is 7.1. The knobby processes are present in B. longicolumnalis sp. nov. from upper hadal zone (6445–7170 m), and they absent in B. kirilli from lower hadal zone (7970–8720 m). A similar difference has been previously noted between the upper and lower hadal Bathycrinus inhabiting the North Pacific trenches: B. rozhnovi and B. longipinnus from the depths 5595–7245 m are with knobby processes, while B. kirilli and B. volubilis from the depths 8175–9735 m lack this processes. The hadal echinoderm fauna of the Palau and Yap trenches includes 19 species. Of these, 15 species are known from the Palau Trench and 10 species—from the Yap Trench.