Alxasaurus

Alxasaurus is an intermediate therizinosauroid from the Early Cretaceous Bayin-Gobi Formation of Inner Mongolia, China. Discovered during the joint Chinese-Canadian expeditions, several well-preserved skeletons of the animal were recovered, providing critical anatomical clues. For decades, fragmentary finds of related animals had puzzled palaeontologists, with some experts grouping them with prosauropods or late-surviving sauropodomorphs. Alxasaurus clearly bridged the gap, demonstrating that the bizarre suite of therizinosaur characteristics, including broad hips, a long neck, small leaf-shaped teeth, and enlarged manual claws, belonged definitively to theropod dinosaurs. Reaching approximately four metres long and weighing several hundred kilograms, it was an upright browser that combed through riparian woodlands, gathering vegetation while maintaining a bipedal stance supported by robust, flat-footed hind legs.

It was crucial in solving the long-standing mystery of therizinosaur evolutionary relationships.

Where and when

Alxasaurus lived in the Early Cretaceous, from 113 to 100.5 million years ago (Albian age). Its remains come from China, in the Bayin-Gobi Formation.

The numbers

Length 4.2 m (estimates run from 3.8 to 4.5 m). Mass about 420 kg. Hip height about 1.5 m. That is 2.5 human-lengths, or 0.38 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 Alxasaurus with a bus Place on the timeline