Beipiaosaurus

Beipiaosaurus is an early therizinosauroid theropod found in the famous Jehol Biota of Liaoning, China. For many years it was the largest known feathered dinosaur, reaching over two metres in length and roughly eighty kilograms in weight. Unlike the predatory carnivorous ancestors of its lineage, Beipiaosaurus adapted to an herbivorous lifestyle, possessing a toothless beak tip, leaf-shaped cheek teeth, and an expansive belly to ferment vegetation. Its hands were tipped with substantial curved claws used to hook leafy branches. Remarkable fossil impressions demonstrate that Beipiaosaurus was cloaked in a dense coat of downy filaments overlain by longer, stiff, broad-filament display feathers along its neck and torso. This dual-layered plumage proves that complex integumentary structures were widespread among large herbivorous maniraptorans, serving both thermal insulation and visual signalling roles.

It preserves two distinct types of feathers, including broad, elongate single filaments used for display.

Where and when

Beipiaosaurus lived in the Early Cretaceous, from 125.8 to 122.5 million years ago (Barremian-Aptian age). Its remains come from China, in the Yixian Formation.

The numbers

Length 2.3 m (estimates run from 2 to 2.5 m). Mass about 67 kg. Hip height about 0.9 m. That is 1.4 human-lengths, or 0.21 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

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