Pegomastax

Phylogeny: Dinosauria > Ornithischia > Saphornithischia > Heterodontosauridae > Heterodontosaurinae

Overview: The only known fossil specimen of Pegomastax consists of a partial and mostly broken skull, discovered in what is now South Africa, back in the mid to late 1960’s. Originally, the fossils were referred to the genus Heterodontosaurus. Heterodontosaurus, of course, is a taxon known for its heterodont dentition, as its name would imply. It possessed different types of teeth in its mouth, including leaf-shearing cheek teeth and large canine-like teeth closer to the front of the jaws. Pegomastax was similar in this regard, also possessing such teeth, but there were a handful of differences. The jaws of Pegomastax were notably more robust and deep, implying it would’ve had a proportionately stronger bite force. Its “tusks” or “canines” were also differently-shaped. One other notable difference was its size – Pegomastax was far smaller than Heterodontosaurus.

Pegomastax and Heterodontosaurus both belong to the family Heterodontosauridae, often seen as one of the most basal lineages within the Ornithischia. Interestingly, despite the two creatures being known from the same region, Pegomastax seems to have been more closely related to the heterodontosaurids in South America. There seems to have been some population exchange going on at the time, which isn’t too surprising, as Africa was still connected to South America at the time (only beginning to break away in the Early Cretaceous). Researchers aren’t entirely certain why this dinosaur and its relatives possessed fang or tusk-like teeth, as most of their teeth suggest a diet of mainly plants. They may’ve been used for foraging or for courtship purposes, with some suggesting they were only present on males, though we can’t be certain if this was the case.