Claosaurus

Claosaurus was a small, primitive duck-billed relative that lived during the Late Cretaceous in central North America. Reaching roughly three and a half to four metres in length, it was considerably smaller and more slender than true hadrosaurids like Edmontosaurus. The type specimen was unearthed from marine chalk in Kansas, indicating that after death the carcass washed down a river and floated far into the Western Interior Seaway before sinking. Claosaurus possessed long feet and an uncrested head, relying on plant material crushed by developing dental batteries. Marsh initially described it as a species of Hadrosaurus before recognising its distinct, more archaic skeletal proportions and assigning it to its own genus.

Its skeleton was recovered from marine chalk deposits, having drifted out to sea as a bloated carcass.

Where and when

Claosaurus lived in the Late Cretaceous, from 87 to 82 million years ago (Coniacian-Campanian age). Its remains come from United States, in the Niobrara Formation.

The numbers

Length 3.8 m (estimates run from 3.5 to 4 m). Mass about 390 kg. Hip height about 1.4 m. That is 2.2 human-lengths, or 0.34 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, first ma, last ma, hip height.

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