Xuanhanosaurus

Xuanhanosaurus (meaning "Xuanhan lizard") is a genus of theropod dinosaur which lived during the Jurassic of China.

The type species Xuanhanosaurus qilixiaensis was named by Dong Zhiming in 1984. The generic name refers to Xuanhan County in Sichuan. The specific name is derived from the town of Qilixia. The holotype specimen, IVPP V.6729, was found in China's Lower Shaximiao Formation, part of the Dashanpu Formation. It consists of a partial skeleton without skull.[1]

Xuanhanosaurus was approximately 4.5 meters (15 ft) in length, with a weight of 250 kilograms (550 lb).[2] Xuanhanosaurus had unusually long arms for a theropod, which were substantially reduced in later theropods such as ''Tyrannosaurus rex. Because of the powerful forelimbs, over two feet long, and the retention of the fourth metacarpal in the hand, Dong suggested that Xuanhanosaurus might have walked on all four legs. If so, it would be the only known four-legged meat-eater among dinosaurs.[1] Later paleontologists have not agreed with Dong's original assessment. They think this dinosaur walked on its hind legs as other theropods did, pronation of the lower arm being impossible. The strong arms could instead have been useful in catching prey.

Assigned by Dong to the Megalosauridae, Xuanhanosaurus was by Roger Benson in 2009 found to be a basal member of the Megalosauroidea.