Khankhuuluu mongoliensis

Khankhuuluu mongoliensis is a roughly four-metre tyrannosauroid from the Bayanshiree Formation. Fossils collected in the 1970s were long assigned to Alectrosaurus, but renewed preparation and comparison revealed a distinct animal. Its shallow skull, relatively long forelimb and lightly built skeleton retain the gracile proportions of earlier tyrannosauroids, while details of the snout and skull roof anticipate features emphasized in later eutyrannosaurs. The describing analysis placed it immediately outside Eutyrannosauria, making it a close evolutionary branch near their origin rather than a demonstrated direct ancestor.

Its fossils occur between approximately 95.9 and 89.6 million years ago. Values shown here are approximate and reflect the current curated seed dataset.

Three partial specimens collectively preserve much of the skull and skeleton, although no individual is complete and several bones reported historically can no longer be located. The skull was long and low with a rounded eye opening, blade-like teeth and modest rugosities rather than the massive, deep profile of Tyrannosaurus. The body was slender, the forelimbs remained proportionally longer, and the hind limbs were built for bipedal movement. Bone fusion and surface texture show that the best material represents a mature animal rather than a juvenile giant tyrannosaur.

• Long, shallow skull with a rounded orbit
• Blade-like teeth rather than the thick crushing teeth of giant tyrannosaurids
• Low facial and skull-roof ornamentation
• Gracile body and relatively long forelimbs
• Combination of primitive tyrannosauroid and emerging eutyrannosaur features

Mongolian palaeontologist Altangerel Perle collected the fossils during 1972-1973 fieldwork at Bayshin Tsav and referred them to Alectrosaurus in 1977. Study of the Ulaanbaatar collections beginning in 2023 led Jared Voris and seven colleagues to name Khankhuuluu mongoliensis in June 2025. The name combines Mongolian khankhuu, prince, with luu, dragon, while mongoliensis honours Mongolia. The specimens remain in the Institute of Paleontology of the Mongolian Academy of Sciences.

Discovery credit: Altangerel Perle, Mongolian field team.

Naming authors: Jared T. Voris, Darla K. Zelenitsky, Yoshitsugu Kobayashi and 5 coauthors.

The Bayanshiree Formation records river channels, floodplains and seasonally dry landscapes in the eastern Gobi. Herbivorous therizinosaurs, hadrosauroids and armoured dinosaurs occupied the same broad formation, alongside other predatory theropods. These fossils accumulated across different sites and intervals, so a formation-level species list is not evidence of one living community at one moment.

Serrated teeth and tyrannosauroid jaw anatomy identify Khankhuuluu as a carnivore. Its lighter skull and body imply a feeding and locomotor system unlike the bone-crushing giant tyrannosaurids, but prey preference and running performance have not been measured directly. No stomach contents, trackway, nest or multi-individual association establishes hunting style or social behaviour.

• Its fossils waited in a collection for about half a century before receiving their own name.
• The name prince dragon contrasts it with the later giant tyrant dinosaurs.
• The best specimen was mature, so its slim build is not simply a juvenile condition.
• A modern skeletal diagram tracks three specimens and flags bones that have been misplaced since 1977.

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1. 01
   A new Mongolian tyrannosauroid and the evolution of Eutyrannosauria

   Jared T. Voris, Darla K. Zelenitsky, Yoshitsugu Kobayashi and 5 coauthors · Nature 642 · 2025

   Open source
2. 02
   Press release: Khankhuuluu mongoliensis

   Hokkaido University · 2025

   Open source