# Asiatyrannus

Asiatyrannus (meaning "Asian tyrant") is an extinct genus of tyrannosaurine theropod dinosaurs from the Late Cretaceous Nanxiong Formation of China. The genus contains a single species, A. xui, known from a single specimen consisting of a skull and partial postcranial skeleton. Asiatyrannus is notable for its deep-snouted skull and small body size, in contrast to the gracile snout and larger size of the contemporary Qianzhousaurus. It represents the southernmost record of an Asian tyrannosaurid.

## Discovery and naming

The Asiatyrannus holotype specimen, ZMNH M30360, was discovered in September 2017 in sediments of the Nanxiong Formation near Shahe Town in Nankang District of Ganzhou City, Jiangxi Province, China. The specimen consists of most of an articulated skull in addition to disarticulated parts of the postcrania, comprising much of the right and left legs and several caudal vertebrae.
In 2024, Zheng et al. described Asiatyrannus xui as a new genus and species of tyrannosaurid based on these fossil remains. The generic name, Asiatyrannus, combines "Asia", the continent of origin, with the Latinised Greek suffix "-tyrannus", meaning "tyrant" or "king". The specific name, xui, honors prominent dinosaur researcher Xu Xing and his contributions to paleontological research in China.

## Description

Asiatyrannus is a small-medium-sized tyrannosaur. Its nearly complete skull measures 47.5 centimetres (18.7 in) long, and it has an estimated body length of 3.5–4 metres (11–13 ft). In comparison, the mature skull of the closely related Nanuqsaurus from the Prince Creek Formation of North America is estimated at 60–70 centimetres (24–28 in). Since Nanuqsaurus likely had a body size similar to Albertosaurus, Asiatyrannus may represent the only tyrannosaurine in this smaller size class. The Asiatyrannus holotype is about half the length of the contemporary Qianzhousaurus. However, the holotype of Asiatyrannus did not belong to a skeletally mature individual, and as such, it would have been larger when fully grown. Nevertheless, it had probably passed through the life stages of most rapid growth, and other tyrannosaurines in similar growth stages are more than twice as large.

## Classification

Using a modified version of the phylogenetic dataset of Carr et al. (2017), Zheng et al. recovered Asiatyrannus as a derived tyrannosaurine member of the Tyrannosauridae, in a polytomy with the North American Nanuqsaurus. These results are displayed in the cladogram below:

## Paleoecology

Asiatyrannus is known from the Nanxiong Formation, which dates to the end of the Maastrichtian age of the late Cretaceous period. Many other dinosaurs have been described from layers of the formation, including the fellow tyrannosaurid Qianzhousaurus. Large teeth indicate the presence of a large, unnamed tyrannosaurid in the ecosystem. Other theropods include therizinosaurids (Nanshiungosaurus) and many oviraptorids (Banji, Corythoraptor, Ganzhousaurus, Huanansaurus, Jiangxisaurus, Nankangia, Shixinggia, and Tongtianlong). The somphospondylan sauropods Gannansaurus and Jiangxititan are also known from the formation. The formation's non-dinosaurian fauna includes crocodilians (Jiangxisuchus), lizards (Chianghsia and Tianyusaurus), and turtles (Jiangxichelys).
The Mongolian Nemegt Formation contains a similar fauna, including the large tyrannosaurine Tarbosaurus, two species of the alioramin Alioramus, and smaller tyrannosauroids such as Bagaraatan.