Oohkotokia

Oohkotokia (/ˌoʊ.oʊkəˈtoʊkiə/ OH-oh-kə-TOH-kee-ə)[citation needed] 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, USA. 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 6 m (19.7 ft) long.

Discovery and naming
The generic name, Oohkotokia, is derived from the Blackfoot animate noun "ooh’kotoka", meaning "large stone" and the Latin suffix "ia" meaning "derived from"; thus "child of stone", which is a reference to its extensive body armor. The generic name also honors the Blackfeet people, on whose land the specimen was found. The specific name, O. horneri, refers to John R. Horner of the Museum of the Rockies, who collected the type specimen.[1] Oohkotokia contains a single type species, Oohkotokia horneri, named and described in 2013 by Paul Penkalski. Penkalski described this genus after finding it in the collection of Montana's Museum of the Rockies where it had been stored for more than three decades.

Description
The holotype of Oohkotokia, MOR 433 consists of a skull that measured 375 mm, axial material, a partial scapula, several thin-walled osteoderms, cervical armour, a very large humerus, and other fragments. Estimates suggest that Oohkotokia was at best 6 m (19.7 ft) long and weighed 2 tons at most.[2] The skull of this genus bears great similarity to skulls that have been referred to Euoplocephalus, but is significant because it has a relatively smooth overall surface texture when compared to the skulls of most other ankylosaurid skulls from the same time period.

Referred specimens
Specimen MOR 363, which consists of fragmentary skull with supraorbital and quadratojugal bosses identical to those observed in holotype MOR 433, which was also found in the Two Medicine Formation, was referred to Oohkotokia. Specimen NSM PV 20381, which was collected in 1995 but not described, and includes an incomplete skull, a pelvic bone, one keeled osteoderm, forelimbs, and hindlimbs without feet. This specimen was once thought to be Euoplocephalus.[3] Specimen TMP 2001.42.19, from the Two Medicine Formation, included a partial skull without teeth, squamosal horns, a distal humerus, osteoderms, a left scapulocoracoid, both ischia, and a complete and well preserved "tail club", which is average-sized - approximately 320 mm wide.

Tail
Like other ankylosaurids, Oohkotokia had an enlarged mass of bone forming a "club" on the end of its tail, made of two enlarged bone lumps. The presence of this type of tail club separates ankylosaurids like Oohkotokia from its close relatives the nodosaurids, who do not have this tail feature. Its tail club was made of several plates of bone, permeated by soft tissue, which allowed the absorption of thousands of pounds of force. The large clubs at the end of their tails may have been used in self-defense, by swinging the club at predators or rivals, or in sexual selection.