Xuanhanosaurus is a genus

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of theropod dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

 which lived during the Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

 of China

China

Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...

.

The type species

Type species

In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

 Xuanhanosaurus qilixiaensis was named by Dong Zhiming

Dong Zhiming

Dong Zhiming , from the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, is one of China's leading paleontologists. He began working at the IVPP in 1962, learning from Yang Zhongjian who was director at the time...

 in 1984. The generic name refers to Xuanhan County

Xuanhan County

Xuanhan County is a county of Sichuan Province, China. It is under the administration of Dazhou city....

 in Sichuan

Sichuan

' , known formerly in the West by its postal map spellings of Szechwan or Szechuan is a province in Southwest China with its capital in Chengdu...

. The specific name is derived from the town of Qilixia. The holotype

Holotype

A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

 specimen, IVPP V.6729, was found in China's

People's Republic of China

China , officially the People's Republic of China , is the most populous country in the world, with over 1.3 billion citizens. Located in East Asia, the country covers approximately 9.6 million square kilometres...

 Lower Shaximiao Formation, part of the Dashanpu Formation

Dashanpu Formation

The Dashanpu Formation is a Mid to Late Jurassic rock formation in China, most notable for the wealth of dinosaurs that have been excavated from the area...

. It consists of a partial skeleton without skull.

Xuanhanosaurus was approximately 4.5 meters (15 ft) in length, with a weight of 250 kilogram

Kilogram

The kilogram or kilogramme , also known as the kilo, is the base unit of mass in the International System of Units and is defined as being equal to the mass of the International Prototype Kilogram , which is almost exactly equal to the mass of one liter of water...

s (550 lb

Pound (mass)

The pound or pound-mass is a unit of mass used in the Imperial, United States customary and other systems of measurement...

). Xuanhanosaurus had unusually long arms for a theropod, which were substantially reduced in later theropods such as Tyrannosaurus rex

Tyrannosaurus

Tyrannosaurus meaning "tyrant," and sauros meaning "lizard") is a genus of coelurosaurian theropod dinosaur. The species Tyrannosaurus rex , commonly abbreviated to T. rex, is a fixture in popular culture. It lived throughout what is now western North America, with a much wider range than other...

. 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. Later paleontologists have not agreed with Dong's original assessment. They think this dinosaur walked on its hind legs as other theropods did, pronation

Pronation

In anatomy, pronation is a rotational movement of the forearm at the radioulnar joint, or of the foot at the subtalar and talocalcaneonavicular joints. For the forearm, when standing in the anatomical position, pronation will move the palm of the hand from an anterior-facing position to a...

 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

Megalosauroidea

Megalosauroidea is a group of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period.-Classification:...

.