Thescelosaurus

Thescelosaurus was a robustly built, bipedal herbivore that lived right at the very end of the Cretaceous period in western North America. Ranging from two and a half to nearly four metres in length, it could weigh up to three hundred kilograms, sporting surprisingly heavy limbs for an ornithopod of its size. Unlike many swift-running relatives, its thigh bone was longer than its shin, suggesting it was built more for steady walking and browsing than high-speed sprinting. Its head bore pointed teeth in the front of the upper jaw alongside grinding cheek teeth, enabling it to consume tough vegetation, stems, and perhaps roots. Several exceptionally preserved skeletons are known, revealing an animal with a sturdy tail stiffened by ossified tendons that balanced its thickset body.

A specimen nicknamed Willow made headlines when internal mineral concretions were mistaken for a fossilised four-chambered heart.

Where and when

Thescelosaurus lived in the Late Cretaceous, from 68 to 66 million years ago (Maastrichtian age). Its remains come from Canada and United States, in the Hell Creek Formation.

The numbers

Length 3.3 m (estimates run from 2.5 to 4 m). Mass about 170 kg. Hip height about 1.1 m. That is 1.9 human-lengths, or 0.29 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

Compare Thescelosaurus with a bus Place on the timeline