Mesozoic hybodont sharks from Asia and their relationships to the genus Ptychodus

Abstract

The affinities of the selachian genus Ptychodus is discussed and Hemiptychodus is here re-introduced as a subgenus characterized by unusual tooth ornamentation pattern.An overview of Asian hybodont genera showing tooth ornamentations pattern similar to that of Ptychodus is given. Lacking a triple-layered enameloid, Ptychodus may be a hybodont shark or a batoid, but both hypotheses are not without problems. Based only on dental characters, hybodont affinities for this genus are favoured here, although the evidence to do so is indeed weak.