Fabrosauridae, the basal family of ornithischian dinosaurs (Reptilia: Ornithopoda)

Abstract

In fabrosaurids the upper jaw is flat and the lower jaw is slender so the 'cheek' teeth are marginal and not inset as is the case in all other ornithischian dinosaurs. The 'cheek' teeth of fabrosaurids have anteroposteriorly expanded crowns but lack wear surfaces formed by tooth to tooth contact. Two genera are recognized from the Triassic-Jurassic boundary of Lesotho with good material previously referred to Fabrosaurus as a new genus that represents the most conservative ornithopod described to date. The anatomy of Nanosaurus (Upper Jurassic, U.S.A.) and Echinodon (Jurassic-Cretaceous boundary, England) is redescribed; in both genera the tooth bearing bone of the lower jaw is deepened posteriorly and in Echinodon there is a true canine tooth in the upper jaw. © 1978 E. Schweizerbart'sche Verlagsbuchhandlung.