Austroraptor osteology + deinocheirid dentaries from Judith River Formation of Montana
169 views
Skip to first unread message
Ben Creisler
Sep 10, 2025, 10:51:26 AM9/10/25
to DinosaurMa...@googlegroups.com
Ben Creisler
======
Tsogtbaatar Chinzorig, Ryuji Takasaki, Kentaro Chiba, Anthony R. Fiorillo, Yoshitsugu Kobayashi, Mototaka Saneyoshi & Shinobu Ishigaki (2025)
A potential deinocheirid ornithomimosaur from the Judith River Formation (Upper Cretaceous: Montana, U.S.A.) and its paleobiogeographic implications
Journal of Vertebrate Paleontology e2536844
doi: https://doi.org/10.1080/02724634.2025.2536844
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2536844
Here, we describe a potential deinocheirid ornithomimosaur from the Upper Cretaceous Judith River Formation of Montana, represented by isolated left and right dentaries. Compared with ornithomimids, the dentaries exhibit distinct morphological features, including a dorsoventrally tall dentary, absence of the dorsal ridge on the cutting edge, and lack of significant symphyseal expansion. These features resemble those observed in deinocheirid ornithomimosaurs, particularly Deinocheirus mirificus, although the fragmentary nature of the new material hinders definitive taxonomic attributions. Computed tomographic imaging reveals the presence of three major neurovascular canals that likely supplied vessels and nerves to the rhamphotheca. These canals communicate with the vascular impressions on the medial surface of the dentary. The vascular impressions indicate blood vessels running within the dermis, indicating an avian-like rhamphotheca nourishing system in Ornithomimosauria. Regardless of its taxonomic status, the dorsoventrally deep dentary differs from known ornithomimosaurs in North America. This finding, therefore, underscores the hidden dinosaur diversity yet to be unveiled, even within well-studied dinosaur-bearing rock units that contribute to our understanding of the paleobiogeography and evolutionary history of ornithomimosaur dinosaurs.
=======
New papers:
Matías J. Motta & Fernando E. Novas (2025)
Osteology of Austroraptor cabazai (Paraves: Theropoda): a southern gigantic unenlagiid from the Late Cretaceous of Patagonia
Historial Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2025.2537843
https://www.tandfonline.com/doi/full/10.1080/08912963.2025.2537843
Austroraptor cabazai is the largest known paravian from Gondwana. The two known specimens consist of cranial and postcranial elements recovered from the Allen Formation (Campanian – Maastrichtian) beds of Río Negro Province, Argentina. The aim of this contribution is to provide a detailed description and analysis of Austroraptor and offering a new interpretation of the available material, cranial morphology, and the diagnosis of the taxon. CT scans revealed internal structures of cranial and vertebral bones, including notable pneumatic structures. Additionally, dental and cranial characteristics shared by Austroraptor and other unenlagiids support the hypothesis of piscivorous habits within this group. Finally, the estimated large size of Austroraptor, in comparison to smaller unenlagiids such as Buitreraptor, suggests a correlation between short arms and relative gigantism among closely related paravians. The present contribution on Austroraptor provides new insight into the anatomical disparity and paleoecology of Southern Hemisphere paravians.
Osteology of Austroraptor cabazai (Paraves: Theropoda): a southern gigantic unenlagiid from the Late Cretaceous of Patagonia
Historial Biology (advance online publication)
doi: https://doi.org/10.1080/08912963.2025.2537843
https://www.tandfonline.com/doi/full/10.1080/08912963.2025.2537843
Austroraptor cabazai is the largest known paravian from Gondwana. The two known specimens consist of cranial and postcranial elements recovered from the Allen Formation (Campanian – Maastrichtian) beds of Río Negro Province, Argentina. The aim of this contribution is to provide a detailed description and analysis of Austroraptor and offering a new interpretation of the available material, cranial morphology, and the diagnosis of the taxon. CT scans revealed internal structures of cranial and vertebral bones, including notable pneumatic structures. Additionally, dental and cranial characteristics shared by Austroraptor and other unenlagiids support the hypothesis of piscivorous habits within this group. Finally, the estimated large size of Austroraptor, in comparison to smaller unenlagiids such as Buitreraptor, suggests a correlation between short arms and relative gigantism among closely related paravians. The present contribution on Austroraptor provides new insight into the anatomical disparity and paleoecology of Southern Hemisphere paravians.
======
Tsogtbaatar Chinzorig, Ryuji Takasaki, Kentaro Chiba, Anthony R. Fiorillo, Yoshitsugu Kobayashi, Mototaka Saneyoshi & Shinobu Ishigaki (2025)
A potential deinocheirid ornithomimosaur from the Judith River Formation (Upper Cretaceous: Montana, U.S.A.) and its paleobiogeographic implications
Journal of Vertebrate Paleontology e2536844
doi: https://doi.org/10.1080/02724634.2025.2536844
https://www.tandfonline.com/doi/full/10.1080/02724634.2025.2536844
Here, we describe a potential deinocheirid ornithomimosaur from the Upper Cretaceous Judith River Formation of Montana, represented by isolated left and right dentaries. Compared with ornithomimids, the dentaries exhibit distinct morphological features, including a dorsoventrally tall dentary, absence of the dorsal ridge on the cutting edge, and lack of significant symphyseal expansion. These features resemble those observed in deinocheirid ornithomimosaurs, particularly Deinocheirus mirificus, although the fragmentary nature of the new material hinders definitive taxonomic attributions. Computed tomographic imaging reveals the presence of three major neurovascular canals that likely supplied vessels and nerves to the rhamphotheca. These canals communicate with the vascular impressions on the medial surface of the dentary. The vascular impressions indicate blood vessels running within the dermis, indicating an avian-like rhamphotheca nourishing system in Ornithomimosauria. Regardless of its taxonomic status, the dorsoventrally deep dentary differs from known ornithomimosaurs in North America. This finding, therefore, underscores the hidden dinosaur diversity yet to be unveiled, even within well-studied dinosaur-bearing rock units that contribute to our understanding of the paleobiogeography and evolutionary history of ornithomimosaur dinosaurs.
=======
Ben Creisler
Jun 15, 2026, 2:55:15 PM (3 days ago) Jun 15
to DinosaurMa...@googlegroups.com
A follow-up comment on the second paper:
Caelan Libke, Gianni Zambonin, Shyong En Pan & Jordan C. Mallon (2026)
No compelling evidence for deinocheirids in the Judith River Formation: a comment on Chinzorig et al. (2025)
Journal of Vertebrate Paleontology e2669278
doi: https://doi.org/10.1080/02724634.2026.2669278
https://www.tandfonline.com/doi/full/10.1080/02724634.2026.2669278
A pair of large ornithomimosaurian dentaries from the Judith River Formation (upper Campanian) of Montana were recently suggested to belong to Deinocheiridae, based on gross morphological features. If true, a deinocheirid from the Upper Cretaceous of Montana would be remarkable, given that none have been found there or in adjacent, penecontemporaneous deposits before; ornithomimosaurs are otherwise represented only by Ornithomimidae. We reconsider those features of the dentary that purportedly differentiate deinocheirids from ornithomimids and find them to be of limited diagnostic value. The incompleteness of the recently assigned Montanan material further frustrates morphometric analysis. Thus, we argue that it cannot confidently be assigned to Deinocheiridae, the taxonomic constituency of which remains unsettled. The Montana specimen is nevertheless significant, as it represents an aberrantly large ornithomimosaur from the Upper Cretaceous of North America.
=====
No compelling evidence for deinocheirids in the Judith River Formation: a comment on Chinzorig et al. (2025)
Journal of Vertebrate Paleontology e2669278
doi: https://doi.org/10.1080/02724634.2026.2669278
https://www.tandfonline.com/doi/full/10.1080/02724634.2026.2669278
A pair of large ornithomimosaurian dentaries from the Judith River Formation (upper Campanian) of Montana were recently suggested to belong to Deinocheiridae, based on gross morphological features. If true, a deinocheirid from the Upper Cretaceous of Montana would be remarkable, given that none have been found there or in adjacent, penecontemporaneous deposits before; ornithomimosaurs are otherwise represented only by Ornithomimidae. We reconsider those features of the dentary that purportedly differentiate deinocheirids from ornithomimids and find them to be of limited diagnostic value. The incompleteness of the recently assigned Montanan material further frustrates morphometric analysis. Thus, we argue that it cannot confidently be assigned to Deinocheiridae, the taxonomic constituency of which remains unsettled. The Montana specimen is nevertheless significant, as it represents an aberrantly large ornithomimosaur from the Upper Cretaceous of North America.
=====
Reply all
Reply to author
Forward
0 new messages