Hybodont sharks from the lower Cretaceous Khok Kruat Formation of Thailand, and hybodont diversity during the Early Cretaceous
G. Cuny, V. Suteethorn, S. Kamha, E. Buffetaut, 2008. "Hybodont sharks from the lower Cretaceous Khok Kruat Formation of Thailand, and hybodont diversity during the Early Cretaceous", Fishes and the Break-up of Pangaea, L. Cavin, A. Longbottom, M. Richter
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Isolated teeth of five hybodont species are described from the Khok Kruat Formation (Aptian): Hybodus aequitridentatus nov. sp., Heteroptychodus steinmanni, Thaiodus ruchae, Khoratodus foreyi nov. gen. et nov. sp., and Acrorhizodus khoratensis. A new family, Thaiodontidae is also erected for Thaiodus and Khoratodus. Two species are recognized inside the genus Heteroptychodus, H. steinmanni and H. chuvalovi nov. comb. These sharks show a wide range of diet and many of them appear to be restricted to a freshwater environment and thus are probably endemic to the Khorat Plateau. However, Thaiodus and Heteroptychodus are also found in deltaic and/or marine environments outside Thailand, but are nevertheless restricted to the Asian continent. It seems that the appearance of three different palaeobiogeographical provinces (Europe, Asia and Africa–South America) around the Tethys during the Early Cretaceous led to the highest diversity at the generic level in the history of hybodont sharks.