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Pegomastax (Greek for "thick jaw"); pronounced PEG-oh-MAST-ax


Woodlands of southern Africa

Historical Period:

Early Jurassic (200 million years ago)

Size and Weight:

About two feet long and five pounds



Distinguishing Characteristics:

Prominent fangs; short bristles on body

About Pegomastax

Some of the most notable dinosaur discoveries don't involve going out into the field with a shovel and pickax, but examining long-forgotten fossil specimens that have been filed away in dank museum basements. That's the case with Pegomastax, which was recently named by Paul Sereno after he examined a neglected collection of fossils from southern Africa, which had been discovered in the early 1960's and stashed in Harvard University's extensive archives.

Pegomastax was certainly an odd-looking dinosaur, at least by the standards of the early Mesozoic Era. About two feet long from head to tail, this close relative of Heterodontosaurus was equipped with a parrot-like beak studded by two prominent canines. The porcupine-like bristles that covered its body are reminiscent of the short, stiff, feathery protrusions of another herbivorous dinosaur, the late Jurassic Tianyulong, which was also an early ornithopod of the heterodontosaur family.

Given its presumed plant-eating diet, why did Pegomastax have such sizable canines? Sereno speculates that this feature evolved not because Pegoamastax snacked occasionally on insects or rotting carcasses, but because it needed to a) defend itself against larger theropod dinosaurs and b) compete for the right to mate. If longer-toothed males were more likely to survive predation, and also more likely to attract females, you can see why natural selection would have favored Pegomastax's fangs.