Unenlagia

Unenlagia was an intriguing, bird-like theropod unearthed from the Late Cretaceous sediments of the Portezuelo Formation in Neuquén, Argentina. Its name derives from the indigenous Mapuche word for half-bird, reflecting its astonishing mixture of avian and non-avian dinosaur characteristics. 5 metres in length, Unenlagia was a gracile, long-legged runner. Its shoulder anatomy was particularly striking: the glenoid cavity faced outward rather than downwards, granting its forelimbs a bird-like range of motion capable of folding and flapping wing movements, even though the animal itself was far too heavy to fly. Classified as the type genus of the Unenlagiinae, Unenlagia represents an evolutionary branch of raptors that flourished across South America, showcasing that key elements of bird flight mechanics had deep and diverse origins among non-avian predatory theropods.

Its shoulder joint was positioned outward like modern birds, allowing its arms to fold and flap.

Where and when

Unenlagia lived in the Late Cretaceous, from 91 to 88 million years ago (Turonian-Coniacian age). Its remains come from Argentina, in the Portezuelo Formation.

The numbers

Length 2.3 m (estimates run from 2 to 2.5 m). Mass about 26 kg. Hip height about 1 m. That is 1.4 human-lengths, or 0.21 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 Unenlagia with a bus Place on the timeline