Cranial anatomy of the Late Permian dicynodont Diictodon, and its bearing on aspects of the taxonomy, palaeobiology and phylogenetic relationships of the genus

grantor: University of TorontoA study of the Late Permian dicynodont 'Diictodon' confirms suggestions that only one species, 'D. feliceps', can be presently recognized. The genus is characterized by features such as a palatal notch, a large dentary table with a medial cutting blade, and the absence of postcanine teeth. Numerous anatomical variations exist within 'Diictodon', but many appear biologically insignificant. However, there is a clear distinction between specimens having canine tusks and those lacking them, as tusked specimens are generally larger and more likely to develop a pineal boss. This probably reflects sexual dimorphism, with the tusked sex almost certainly being the male. A phylogenetic analysis of dicynodonts indicates that previous analyses are correct in identifying 'Robertia' as the sister-group of ' Diictodon' and 'Dicynodon' and 'Aulacephalodon ' as close relatives of 'Lystrosaurus'. However, the results suggest that 'Endothiodon', rather than 'Eodicynodon ', may be the most basal known dicynodont.M.Sc