Raptorex NT


Raptorex is a genus of small tyrannosaurid that lived in the Late Cretaceous (70 mya) of Mongolia or northeastern China. When Raptorex was found the paleontologist thought it was a T. rex but smaller. It was almost as big as a Velociraptor and had feathers. It was typically said to be a juvenile Tarbosaurus bataar, but a recent study has supported its validity.


Raptorex holotype


According to Peter Larson, who attempted to re-trace the origins of the specimen, the holotype fossil of Raptorex (currently designated LH PV18 and housed in the collections of the Long Hao Institute of Geology and Paleontology in Hohhot, Inner Mongolia, China) was purchased from a Mongolian fossil dealer by an American businessman in Tokyo, Japan, and subsequently taken to the United States, where it was again put up for sale at the Tucson, Arizona Gem, Mineral and Fossil Show. There it was sold by Hollis Butts to Dr. Henry Kriegstein, an ophthalmologist and fossil collector. Up until this point, the specimen had been identified as a juvenile specimen of Tarbosaurus, which had been collected from Mongolia. Kriegstein notified American paleontologist Paul Sereno of the specimen, who proposed it represented a subadult of a new species from the Yixian Formation of China. Sereno arranged to publish a description of the specimen and to have it sent to China, from where he assumed it had been smuggled.


The only known Raptorex specimen shows the same basic proportions as juvenile tyrannosaurids: a comparatively large and solidly-constructed skull, long legs with adaptations for running, and tiny, two-fingered forelimbs. This is in contrast with more basal tyrannosauroids such as Dilong, which retained features characteristic of more basal coelurosaurs such as a small head and long, three-fingered forelimbs.

The holotype is thought to be a young juvenile who died at 3 years old. It is estimated to be 3 metres long and weigh 65 kilograms when it was alive.

Interpretation and controversy[]

In his description, Sereno and his co-workers claimed that the holotype was a near-adult that was about 6 years old when it died, and that it came from the Yixian Formation of China. However, in October 2010, an online Nature News report challenged this interpretation, claiming that it was actually a juvenile Tarbosaurus and that its Early Cretaceous age was incorrect. A year later, in June 2011, a more detailed restudy showed that the holotype was actually a young juvenile that was at least 3 years old during its death. After studying a fish bone found with the specimen that Sereno claimed was from the genus Lycoptera, it was found out that it was more likely to be an ellimmichthyiform fish that came from the Nemegt Formation. This would mean that the Raptorex holotype wasn't originally from the Yixian Formation and rather from the Nemegt Formation.

In 2022, results from a restudy of the Raptorex holotype was included within an article discussing the tyrannosauroids of the Iren Dabasu Formation by researcher Thomas Carr. While Carr agreed that the holotype was a 3 year old juvenile, he found it to be a valid taxon because of several features of its skull that was not found in other tyrannosaurids. In addition to that, Carr pointed out that the holotype lacked a subcutaneous flange of the maxilla, a feature that is unique to juvenile Tarbosaurus.

In the Media[]

  • Raptorex was seen as a life Sized Head & Neck in the National Geographic Documentary Bizarre Dinosaurs.
  • It also appeared in an episode of Dinosaur Train “Buddy explores The Tyrannosaurs”.

    Raptorex in Dinosaur train