An Unusual Cladid (Crinoidea, Echinodermata) from the Pennsylvanian of the Staritsa District (Tver Region).

The cladid crinoid Kholokholnyacrinus ilkhovskyi gen. et sp. nov. is described based on a very large cup from the Pennsylvanian (Kashirian Regional Substage, Smedva Formation) of the Rzhev–Staritsa Volga Region. The new taxon is characterized by a complex of morphological characters in the structure of the crown and arms, such as a disarticulated basal circlet, very low brachials in close contact with each other and with anal sac plates, fixed proximal arms, etc., by which it differs strongly from most other cladids. The uniqueness of the morphological characters indicates that the new genus should be assigned to a new family of cladid crinoids. Paleoecological aspects and systematics of the new crinoid genus are discussed. [ABSTRACT FROM AUTHOR]