Khankhuuluu ( khahn-KOO-loo; lit. 'dragon prince') is an extinct genus of early tyrannosauroid theropod dinosaurs from the Late Cretaceous of what is now the Gobi Desert in Mongolia. The genus contains a single species, Khankhuuluu mongoliensis, known from several skull bones and two partial skeletons, including shoulder, pelvic, and hindlimb bones, and several vertebrae from the back and tail. The remains were discovered in 1972 and 1973 and first described in 1977 as belonging to the Chinese Alectrosaurus. Later researchers recognized the uniqueness of the bones, and they were eventually named as belonging to a new species in 2025. Khankhuuluu is a medium-sized tyrannosauroid with a shallow skull and long, slender legs. Its skeleton demonstrates a unique combination of anatomical traits seen in both earlier-diverging (basal) tyrannosauroids and the later-diverging (derived) tyrannosaurids. Khankhuuluu is known from the Bayanshiree Formation, which dates to around the Turonian–Santonian ages. The formation has yielded abundant fossils of diverse dinosaurs including various theropods, ankylosaurs, marginocephalians, hadrosauroids, and sauropods, in addition to pterosaurs, crocodylomorphs, turtles, and fish. These fossils were deposited in an environment with meandering rivers.
Discovery and naming
The Khankhuuluu fossil material was discovered in 1972–1973 in outcrops of the Bayanshiree Formation (Baishin-Tsav locality) in southeastern Mongolia. The collected specimens are now accessioned at the Mongolian Academy of Sciences. The first specimen MPC-D 100/50, comprises a partial skeleton including cranial bones (the nasal, incomplete left lacrimal, parts of both quadrates, a vomer, and parts of both ectopterygoids and pterygoids), several vertebrae (three dorsals and the last 17 caudal vertebrae), a furcula, the left scapulocoracoid, and the left metatarsal III. The second specimen, MPC-D 100/51, also includes cranial bones (the right postorbital, quadratojugal, and quadrate), a partial left pelvic girdle (ischium and partial ilium), part of the right hindlimb (proximal part of the metatarsus and four toe bones), and part of the left hindlimb (incomplete tibia). These remains were first described by Mongolian paleontologist Altangerel Perle in 1977. He assigned them to the Chinese species Alectrosaurus olseni, known from the Iren Dabasu Formation, claiming that the bones provided evidence that these two formations were synchronous. In 2012, Tsuihiji and colleagues described an isolated left frontal bone, MPC-D 102/4, from the Bayanshiree Formation (Tsaagan Teg region). In a separate paper published that year, Averianov and Hans-Dieter Sues described several isolated cranial and postcranial tyrannosauroid remains (later named as a new taxon, Timurlengia) from the Bissekty Formation of Uzbekistan. Citing tyrannosaur researcher Thomas Carr, they noted that the Bayanshiree "Alectrosaurus" material could not be definitively referred to this genus. In 2025, Jared T. Voris and colleagues described Khankhuuluu mongoliensis as a new genus and species of early tyrannosauroids based on these fossil remains. They noted that several skull bones (a premaxilla, maxilla, jugal, and dentary) and a manual ungual (hand claw), originally described by Perle in 1977, could not be found to be studied. MPC-D 100/50 was established as the holotype (name-bearing) specimen. MPC-D 100/51 and MPC-D 102/4 were also referred to the species based on anatomical similarities with the holotype; MPC-D 100/50 and MPC-D 100/51 both preserve a quadrate that demonstrates two autapomorphies (unique derived traits). While neither of these specimens preserves a frontal, MPC-D 100/50 includes a nasal, which articulates with the frontal. The morphology of the contact between these two bones is consistent across both specimens, indicating they belong to the same species. The generic name, Khankhuuluu, combines khankhuu (a Latinization of the Mongolian ханхүү), meaning "prince", and luu (from the Mongolian луу), meaning "dragon". The term "prince" was chosen to refer to the predecessory position of Khankhuuluu in the tyrannosaur lineage, relative to the much larger 'tyrant lizards' that lived millions of years later. The specific name, mongoliensis, references the country from which the fossil material was discovered. The intended translation of the full binomial name is "Dragon Prince of Mongolia".
Description
Khankhuuluu is a medium-sized tyrannosauroid. None of the known specimens preserve a complete skull. However, the cranial bones of the two more complete specimens, MPC-D 100/50 and MPC-D 100/51, suggest a total skull length between 60 and 70 centimetres (24–28 in) long. MPC-D 100/51 is slightly smaller than the holotype and has a femur 66.8 centimetres (26.3 in) long. Both specimens likely belong to mature individuals. Sexual maturity is suggested by the development of ornamentation on the nasal and lacrimal. Skeletal maturity is implied by the close of the neurocentral sutures of the dorsal vertebrae, as well as the interdigitating frontal sutural surface of the postorbital. Estimates suggest Khankhuuluu was around 2 m (6.6 ft) tall at the hips and at least twice that in length. It may have weighed around 750 kg (1,650 lb). Khankhuuluu is notable as it illuminates the evolutionary patterns of tyrannosauroid dinosaurs. While some of its anatomical characteristics are more reminiscent of earlier-diverging species, many other features more closely resemble later members of the Tyrannosauridae.
Skull
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