Alectrosaurus

Alectrosaurus was a medium-sized carnivorous dinosaur that lived across eastern Asia during the early part of the Late Cretaceous. As a basal tyrannosauroid, it lacked the massive bone-crushing skull of the later, gigantic tyrannosaurids, retaining instead an athletic build suited for rapid sprints. The genus was discovered in the 1920s by the American Museum of Natural History expeditions to Inner Mongolia. Early descriptions mistakenly associated oversized arms and claws from a therizinosauroid with its hind limbs, causing decades of confusion until more complete fossils clarified its anatomy. It stretched to around five metres in total length and stood about shoulder-high to a human adult. In its semi-arid ecosystem, Alectrosaurus would have hunted smaller ornithischians and juvenile sauropods, filling the niche of a swift mid-tier terrestrial predator.

Originally described with forelimb elements that actually belonged to a therizinosaur, Alectrosaurus is now recognised as a moderately sized basal tyrannosauroid.

Where and when

Alectrosaurus lived in the Late Cretaceous, from 96 to 90 million years ago (Cenomanian-Turonian age). Its remains come from Mongolia and China, in the Iren Dabasu Formation.

The numbers

Length 4.8 m (estimates run from 4.5 to 5 m). Mass about 520 kg. Hip height about 1.5 m. That is 2.8 human-lengths, or 0.43 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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