Asiatyrannus and Raptorex likely Tarbosaurus + ornithomimosaur vertebra from British Columbia + sauropod from Upper Cretaceous of Edcuador

[Ben Creisler]

Ben Creisler

bcre...@gmail.com

New papers:

Free pdf:

Gorm Skouboe Raun, Colton Chase Coppock, Demchig Badamgarav, Khishigjav Tsogtbaatar & Philip John Currie (2026)
Taxonomic reassessment of juvenile tyrannosaurine specimens from Asia reveal large biogeographic ranges in tyrannosaurids
Cretaceous Research 106412
doi: https://doi.org/10.1016/j.cretres.2026.106412
https://www.sciencedirect.com/science/article/pii/S0195667126001011


Highlights

“Asiatyrannus xui” and “Raptorex kriegsteini” are likely junior synonyms of Tarbosaurus bataar.
Results support that the biogeographic range of Tarbosaurus bataar is larger than 2300 km.
Comparison to modern species suggests that we underestimate the ranges of theropod dinosaurs.

ABSTRACT

The recently named tyrannosaurid, Asiatyrannus xui, from the Nanxiong Formation of southeastern China bears a striking resemblance to juvenile specimens of Tarbosaurus bataar, warranting a reassessment of taxa named based on material with known juvenile characteristics. Similarly, the long contested Raptorex kriegsteini also possesses numerous cranial morphologies that are shared with both juvenile specimens of Tarbosaurus bataar and Asiatyrannus xui. Here the taxonomic affinities of Asiatyrannus xui and Raptorex kriegsteini are reassessed based on proposed diagnostic characters. Morphological evidence suggests that both “Asiatyrannus xui” and “Raptorex kriegsteini” are likely junior synonyms of Tarbosaurus bataar. The referral of “Raptorex kriegsteini” to Tarbosaurus bataar is supported by the stratigraphic work of previous authors, the presence of Tarbosaurus bataar autapomorphies in “Raptorex kriegsteini”, and the widespread occurrence of previously reported Raptorex kriegsteini autapomorphies in specimens of Tarbosaurus bataar. The referral of “Asiatyrannus xui” to Tarbosaurus bataar is supported by the presence of Tarbosaurus bataar autapomorphies, by morphologies shared in juvenile and adolescent specimens, and by a lack of apomorphies in “Asiatyrannus xui” that are not present in Tarbosaurus bataar. The identification of a Tarbosaurus bataar specimen from the Nanxiong Formation of China drastically expands the known biogeographic range of the species and aligns with the reported ranges of some North American Tyrannosaurids. The evidence suggests that the known ranges for many tyrannosaurids are vastly underestimated and likely rivalled ranges of modern carnivorans.

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Free pdf:

Victoria M. Arbour, Timon S. Bullard, and David C. Evans (2026)
An ornithomimosaur from the Campanian Cedar District Formation (Nanaimo Group) of Denman Island, British Columbia, Canada
FACETS 11: 1-7
doi: https://doi.org/10.1139/facets-2023-0079
https://www.facetsjournal.com/doi/10.1139/facets-2023-0079
https://www.sciencedirect.com/org/science/article/pii/S2371167126000360

Free pdf:
https://www.facetsjournal.com/doi/epdf/10.1139/facets-2023-0079


Despite decades of intensive collecting effort in the Upper Cretaceous Nanaimo Group of Vancouver Island, no definitive dinosaur remains have been reported. Here we describe an isolated theropod caudal vertebra from marine sediments of the Campanian-aged Cedar District Formation of Denman Island, representing only the second report of dinosaur bones from the Nanaimo Group and the first report from Canadian outcrops. The proportions of the centrum and prezygapophyses are consistent with those of ornithomimosaurs, but the specimen cannot be identified more precisely. The vertebra was likely transported from the western margin of North America to the east. The Nanaimo Group was deposited at least 600 km south of its present position, and this ornithomimosaur likely lived at a similar palaeolatitude to contemporaneous dinosaur faunas in the Two Medicine and Judith River formations in the Western Interior.

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Santiago Balcázar-Loaiza, Sebastián Apesteguía, Pablo A. Gallina, Oswaldo Guzmán & Corina Campos (2026)
First record of a dinosaur for the Oriente Basin at the Tena Formation (Upper Cretaceous) of Ecuador
Cretaceous Research 106413
doi: https://doi.org/10.1016/j.cretres.2026.106413
https://www.sciencedirect.com/science/article/abs/pii/S0195667126001023


Highlights

First dinosaur record for the Oriente Basin at the Tena Formation (Maastrichtian), Ecuador
Fossils suggest a non-saltasaurine, likely colossosaurian titanosaur.
Evidence of higher sauropod diversity in the Late Cretaceous of Ecuador.
Paleoenvironment is interpreted as a coastal lagoon with marine incursions.

ABSTRACT

New sauropod materials from Ecuador were found in rocks of the upper part of the Tena Formation (Maastrichtian, Upper Cretaceous) at the Napo River area. They consist of an associated forelimb including a partial humerus and five partial metacarpals. The specimen differs from the previous saltasaurine titanosaur finding in Loja for being larger and more slender, in a way that might be consistent with those of colossosaurian titanosaurs. The Tena Formation was deposited in a lagoon-like transitional environment with marine incursions, consistent with regional geological evolution models in the context of the Andean uplift. This discovery expands our knowledge of sauropod diversity in the Late Cretaceous of northern South America and corroborates a wider distribution of titanosaurs in the region. Since the material was first found and excavated by non-trained people part of the bones were lost, preserving only some bones and early photos.

[Gregory Paul]

This is interesting in that according to their SVP abstract last year Raun et al. are about to split Nemegt Tarbosaurus into multiple species. Not that Asiatyrannus and Raptorex don't belong in the genus or close to it, I noted the latter did and a reason why in my Mesozoic paper last year. 

GSPaul