Open Paleo

Polyodontosaurus

Gilmore, 1932 pol-ee-o-DON-to-SAWR-us Nomen dubium

From Greek 'polys' meaning 'many', 'odon' meaning 'tooth', and 'sauros' meaning 'lizard'; meaning 'many-toothed lizard', for the high alveolus count of the type dentary.

83.6–72.2 million years ago Campanian, Late Cretaceous
Late Cretaceous stages

Polyodontosaurus is a dubious genus of troodontid dinosaur named in 1932 by Charles W. Gilmore for a single left dentary from the Dinosaur Park Formation of Alberta, Canada, which Gilmore originally took for a large lizard. Sternberg (1951) recognized the jaw as theropod instead, and later workers referred the specimen to the better-known Dinosaur Park troodontids before it was declared a nomen dubium. The only known species is the type, P. grandis.

Under dispute

Polyodontosaurus grandis rests on a single troodontid dentary, CMN 8540, and successive workers have folded it into the Dinosaur Park troodontid complex: Carpenter (1982) listed it in the synonymy of Saurornithoides inequalis, Currie (1987) treated the dentary as Troodon material, and Varricchio and colleagues (2025) carry it in the synonymy of Troodon formosus. Van der Reest and Currie (2017) declared it a nomen dubium on two grounds — troodontid dentary morphology is not variable enough to distinguish taxa, and the reported provenance of CMN 8540 cannot be reconciled with the exposures at the stated locality, so its horizon within the formation is unrecoverable. They raised the possibility that Latenivenatrix mcmasterae represents the same taxon but declined it as untestable, and no synonymy in either direction has been proposed. The genus cannot be placed below family level and is retained at Troodontidae incertae sedis.

Species

Polyodontosaurus grandis Gilmore, 1932 Nomen dubium

Type species

From Latin 'grandis' meaning 'large' or 'great'.

Holotype
CMN 8540 , Canadian Museum of Nature
Material
Nearly complete left dentary, edentulous, 117.5 mm long and bearing 35 alveoli
Horizon
Dinosaur Park Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
Railway Cut badlands, Steveville area, Alberta, Canada Gilmore's locality is internally inconsistent, which van der Reest and Currie (2017) give as part of their reason for treating the species as a nomen dubium. Gilmore reports the site as about three miles southwest of the mouth of Berry Creek, a bearing that does not reach the Railway Cut badlands Gilmore also names.

References

  1. Gilmore, C. W. (1932). A new fossil lizard from the Belly River Formation of Alberta. Transactions of the Royal Society of Canada, section 4, series 3 26: 117-120. gilmore1932a
  2. Carpenter, K. (1982). Baby dinosaurs from the Late Cretaceous Lance and Hell Creek formations and a description of a new species of theropod. Contributions to Geology, University of Wyoming 20(2): 123-134. doi:10.15468/gcrned

    Listed Polyodontosaurus grandis in the synonymy of Saurornithoides inequalis

    carpenter1982a
  3. Currie, P. J. (1987). Bird-like characteristics of the jaws and teeth of troodontid theropods (Dinosauria, Saurischia). Journal of Vertebrate Paleontology 7(1): 72-81. Informa UK Limited. doi:10.1080/02724634.1987.10011638

    Described and figured the holotype dentary CMN 8540 as material of Troodon

    currie1987a
  4. van der Reest, A. J.; Currie, P. J. (2017). Troodontids (Theropoda) from the Dinosaur Park Formation, Alberta, with a description of a unique new taxon: implications for deinonychosaur diversity in North America. Canadian Journal of Earth Sciences 54(9): 919-935. doi:10.1139/cjes-2017-0031

    Declared Polyodontosaurus grandis a nomen dubium on undiagnostic dentary morphology and unrecoverable provenance

    vanderreest2017a
  5. Varricchio, D. J.; Hogan, J. D.; Gardner, J. D. (2025). Troodontid specimens from the Cretaceous Two Medicine Formation of Montana (USA) and the validity of Troodon formosus. Journal of Paleontology 99(1): 219-240. Cambridge University Press (CUP). doi:10.1017/jpa.2024.67

    Carried Polyodontosaurus grandis in the synonymy of Troodon formosus

    varricchio2025a
  6. Sternberg, C. M. (1951). The lizard Chamops from the Wapiti Formation of northern Alberta: Polyodontosaurus grandis not a lizard. National Museum of Canada Bulletin 123: 256-258. doi:10.4095/105060 sternberg1951b