CRANIAL ANATOMY AND TAXONOMY OF THE LATE PERMIAN DICYNODONT DI1CTODON

摘要

Reexamination of the cranial anatomy of the abundant Late Permian dicynodont Diictodon confirms suggestions that only one species, D. feliceps, is recognizable. This monotypic genus is highly distinctive, being characterized by such features as a palatal notch, a large dentary table with a medial cutting blade, and the absence of postcanine teeth. Numerous anatomical variations exist within D. feliceps, but many appear biologically insignificant and show no apparent correlation with one another of with locality or slratigraphic position. However, statistical analysis reveals the presence of several features that correlate with the presenee of canine tusks, including an occipitally positioned postparietal bone and the presence of a boss surrounding the pineal opening. This suggests that tusked and tuskless specimens do indeed represent distinct biological categories, but it seems highly probable that they are divisions within a single species (most probably opposite sexes) rather than distinct species. It is hoped that the detailed osteological description of the Diictodon skull presented here will provide useful data for future phyloge-netie analyses of dicynodonts.