Animantarx

Animantarx was a moderately sized, heavily armoured nodosaurid dinosaur that lived in what is now Utah during the mid-Cretaceous period. 5 metres in total length and weighing roughly one tonne, it had a low-slung, stocky quadrupedal frame protected by extensive bony plates and keeled scutes. Unlike club-tailed ankylosaurids, Animantarx lacked a weaponised tail club, relying instead on passive dermal defence and compact musculature. The discovery of Animantarx is uniquely memorable: researcher Ramal Jones located its subterranean skeleton by detecting subtle uranium radioactivity emanating from the mineralised bones. Found in the Mussentuchit Member of the Cedar Mountain Formation, this plant-eater cropped low-growing ferns, cycads, and shrubs in a warm, river-fed floodplain.

Its fossil was discovered purely through a radiological survey detecting slightly radioactive bones underground.

Where and when

Animantarx lived in the Early Cretaceous, from 104 to 98 million years ago (Albian-Cenomanian age). Its remains come from United States, in the Cedar Mountain Formation.

The numbers

Length 3.3 m (estimates run from 3 to 3.5 m). Mass about 980 kg. Hip height about 1 m. That is 1.9 human-lengths, or 0.29 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.

Compare Animantarx with a bus Place on the timeline