Heterodontosaurus

Phylogeny: Dinosauria > Ornithischia > Saphornithischia > Heterodontosauridae > Heterodontosaurinae

Overview: As the name “different-toothed lizard” would imply, Heterodontosaurus possessed a few different types of teeth throughout its jaws, all situated behind a beak - beaks being common to all ornithischian dinosaurs. Toward the tip of the upper jaw were a few pointed teeth, situated just in front of a pair of enlarged, tusk-like canines on the bottom jaw. Behind them were situated rows of tightly-packed, chisel-shaped teeth that were well suited for tearing apart vegetation. These rear teeth imply Heterodontosaurus was mostly herbivorous, though it’s not unreasonable to assume it supplemented this diet with insects or small vertebrates. The beak, which in life was coated by a sheath of keratin, was useful for snipping stems or branches. Heterodontosaurus may’ve employed its “tusks” to break apart tougher plants, to dig up roots or possibly even for sexual display purposes. Some speculate only males had these canines, though we can’t be certain as determining sex from bones alone can be extremely difficult for most dinosaurs.

Heterodontosaurus only grew to be a little over a meter in length, so it wasn’t an overly large dinosaur, even for the Early Jurassic. Like all basal ornithischians, it was a biped. Evasion would’ve been one of its main means of defense against predators, though its teeth could probably inflict painful bites when caught. This dinosaur is the namesake of the family Heterodontosauridae, which represents some of the earliest confirmed ornithischian dinosaurs. Earlier potential ornithischians are of debated phylogenetic status or may not even be true dinosaurs at all. Heterodontosaurids were, on the whole, smaller-sized herbivores that mainly lived during the Jurassic, though at least a few of them persisted into the Early Cretaceous. Some of them, like Pegomastax, also possessed enlarged canines. China’s Tianyulong has even been found with preserved bristle-like integument or proto-feathers, implying Heterodontosaurus had them too. Many of these dinosaurs, including Heterodontosaurus itself, are known from what is now South Africa. Described as a genus in 1962, Heterodontosaurus is mainly known from the upper layers of the famous Elliot Formation.