Revision ofTenticospiriferTien, 1938, and similar spiriferid brachiopod genera from the Late Devonian (Frasnian) of Eurasia, North America, and Australia

Abstract

The cyrtospiriferid brachiopod genusTenticospiriferTien, 1938, is revised based on restudy of the type species from the Frasnian (Late Devonian) of the Russian Platform. As revised the genus includes cyrtospiriferid species with pyramidal ventral valves, catacline ventral interareas, a narrow delthyrium, few sinal plications, and lack a median dorsal septum and pseudodeltidium. All species retained in the genus are of Givetian and Frasnian age. All Famennian age species described from South China and North America are rejected from the genus. It appears thatTenticospiriferevolved during the early Givetian in western Europe and remained endemic to that region during the remainder of the Givetian. Successive migrations ofTenticospiriferfrom eastern Laurussia to North America, then to South China and possibly Australia, coincided with middle and late Frasnian eustatic sea level rises, respectively. The North American speciesSpirifera cyrtinaformisHall and Whitfield, 1872, and related species identified asTenticospiriferby North American workers, are reassigned toConispiriferLyashenko, 1985. Its immigration to and widespread dispersal in carbonate platforms of western Laurussia, northern Gondwana and tropical island arcs (?) coincided with a major late Frasnian eustatic sea level rise. The new family Conispiriferidae is proposed withConispiriferLyashenko, 1985, selected as the type genus. The new family also includes the new genusPyramidaspiriferwithPlatyrachella altaFenton and Fenton, 1924, proposed as the type species. The affinity of the new family remains uncertain pending restudy of key genera currently included in the Superfamily Cyrtospiriferoidea. Available data from the Devonian brachiopod literature indicate that species ofPyramidaspiriferare restricted to late Frasnian deposits of central and western North America.