Open Paleo

Oohkotokia

Penkalski, 2013 OH-oh-kuh-TOH-kee-uh /ˌoʊ.oʊkəˈtoʊkiə/ Disputed

From Blackfoot 'ooh'kotoka' meaning 'large stone' and Latin suffix '-ia' meaning 'derived from', giving the meaning 'child of stone', referring to its extensive body armor; the name also honors the Blackfoot people on whose land the specimen was found.

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

Oohkotokia is a genus of ankylosaurid dinosaur within the subfamily Ankylosaurinae. It is known from the upper levels of the Two Medicine Formation (late Campanian stage, about 74 Ma ago) of Montana, United States. The discovery of Oohkotokia supports that Ankylosaurine dinosaurs existed and flourished continuously in Montana and/or Alberta throughout the late Campanian and early Maastrichtian stages in the Late Cretaceous period. It was a large, heavily built, quadrupedal, herbivore, that could grow up to 5 meters (16 ft) long and weigh up to 2 metric tons (2.2 short tons).

Under dispute

The validity of Oohkotokia is contested. Arbour and Currie (2015) treated it as a junior synonym of Scolosaurus cutleri, whereas Penkalski (2018) and Wiersma and Irmis (2018) found it distinct. Retained as a valid ankylosaurine pending consensus.

Diagnosis

  1. Prominent horn-like trihedral squamosal bosses with rounded unkeeled caudal apex
  2. Small median nasal plate on skull roof undistinguished from surrounding osteoderms
  3. Broad smooth quadratojugal bosses with strong caudal curvature
  4. Small occipital condyle relative to basal skull length
  5. Large orbit relative to other Campanian North American ankylosaurids
  6. Osteoderms basally excavated with smooth finely pitted external surface texture
  7. Steeply-pitched triangular lateral caudal osteoderms

Species

Oohkotokia horneri Penkalski, 2013 Disputed

Type species

Named for John R. Horner of the Museum of the Rockies, who collected the type specimen.

Holotype
MOR 433 , Museum of the Rockies
Material
Skull and fragmentary skeleton
Horizon
upper Two Medicine Formation, Campanian, Late Cretaceous , 83.6–72.2 million years ago
Locality
MOR locality TM-034, Montana, United States

References

  1. Penkalski, P. (2013). A new ankylosaurid from the late Cretaceous Two Medicine Formation of Montana, USA. Acta Palaeontologica Polonica. Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). doi:10.4202/app.2012.0125 penkalski2013a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026a
  3. Arbour, V. M.; Currie, P. J. (2015). Systematics, phylogeny and palaeobiogeography of the ankylosaurid dinosaurs. Journal of Systematic Palaeontology 14(5): 385-444. Informa UK Limited. doi:10.1080/14772019.2015.1059985

    Treated Oohkotokia as a junior synonym of Scolosaurus cutleri.

    arbour2015a
  4. Wiersma, J. P.; Irmis, R. B. (2018). A new southern Laramidian ankylosaurid, Akainacephalus johnsoni gen. et sp. nov., from the upper Campanian Kaiparowits Formation of southern Utah, USA. PeerJ 6: e5016. PeerJ. doi:10.7717/peerj.5016

    Found Oohkotokia distinct from Scolosaurus cutleri.

    wiersma2018a
  5. Penkalski, P. (2018). Revised systematics of the armoured dinosaur Euoplocephalus and its allies. Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen 287(3): 261-306. Schweizerbart. doi:10.1127/njgpa/2018/0717

    Found Oohkotokia distinct rather than a synonym of Scolosaurus.

    penkalski2018a