Stegoceras

Stegoceras is one of the best-known and most extensively studied pachycephalosaurs. Living in western North America during the Late Cretaceous, it grew to about two and a half metres in length and weighed around forty kilograms, making it roughly the size of a goat. Its prominent skull dome was bordered by small bony shelves and knobs along the back and sides. While pachycephalosaur remains usually consist exclusively of isolated domes, several articulated skeletons of Stegoceras have been found, revealing a slender body, short arms, and stiffened tail tendons. Biomechanical studies and computed tomography scans have revealed that its dome was structured with dense outer layers surrounding vascular, spongy bone, an architecture capable of resisting heavy impacts during intraspecific shoving or flank-butting contests.

CT scans showed its dome had an internal shock-absorbing structure suited for intraspecific head-butting.

Where and when

Stegoceras lived in the Late Cretaceous, from 76.5 to 74.5 million years ago (Campanian age). Its remains come from Canada and United States, in the Dinosaur Park Formation.

The numbers

Length 2.3 m (estimates run from 2 to 2.5 m). Mass about 34 kg. Hip height about 0.8 m. That is 1.4 human-lengths, or 0.21 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, hip height.

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