Three new genera of stalked crinoids of the family Hyocrinidae (Echinodermata, Crinoidea)

摘要

Three new species of the family Hyocrinidae, Ailsacrinus klikushini gen. et sp. n. (North-Western Basin of the Pacific, 2915-3015 m), Ailsacrinus peripterus gen et sp. n., Feracrinus aculeatus gen. et sp. n, (Kuril-Kamchatka Trench region, 3200-3275 m), belonging to two new genera were collected during expeditions of the research vessel "Vityaz'". Morphology of the cotype Ptilocrinus antarcticus Bather, 19{)8 (Museum of National History. London), separating into the new genus Dumetocrinus gen. n., was studied. Ailsacrinus gen. n. and Feracrinus gen. n. differ from other Hyocrinidae by the presence of large thorns on proximal brachials. Dumetocrinus gen. n., bears thorns only on pinnulas. The following features are characteristic of all three genera: the first pinnula occurs always at brachial 4; brachials 5 and 6 are joined by a syzygy; there are additional plates separating gonads from ambulacral grooves in the pinnula skeleton. Ailsacrinus gen. n. is characterized by the presence of three distinct sutures in basal ring, low tegmen, little number of brachials between two neighboring syzygies and undivided columnals of the stalk. Both Feracrinus gen. n and Dumetocrinus gen. n. have fused basal ring, high tegmen, large number of brachials between two neighboring syzygies and columnals of the proximal stalk part are divided into segments. Dumetocrinus gen. n has a unique structure of genital expansions: they consist of three rows of additional plates on both sides.