A new omalodontid-like shark from the Late Devonian (Famennian) of western Siberia, Russia

摘要

Teeth belonging to a new chondrichthyan, Siberiodus mirabilis gen. et sp. nov., are described from the Famennian Pescherka and Podonino Formations of the Kuznetsk Basin, and the Cheybekkiol' Formation of Gorniy Altay, western Siberia. The Pescherka Formation is early Famennian based on conodonts (crepida-marginifera conodont zones), and the Podonino Formation is late Famennian (trachytera-expansa zones). The Cheybekkiol' Formation is also early Famennian (Middle triangularis-Ea?y rhomboidea zones). The teeth of the several omalodontid-like taxa are characterised by a base with a labial extension, and a reduced lingual part, and most show asymmetry of the crown. The new taxon differs from other such forms in the external and histological structures of the crown, and the type ofvascularisation system. It is suggested that chondrichthyan teeth with a labial base extension could have arisen separately in several shark groups.