アメリカのユタ州から、およそ7500万年前という、ティラノサウルスの基盤的な新種が発見されました。

Teratophoneus: Utah’s Monstrous, Murderous New Tyrannosaur Found in the 75-million-year-old rock of Utah’s Grand Staircase-Escalante National Monument, Teratophoneus is known from a partial skull and additional elements from the rest of the skeleton. Its head was short—a departure from the typically long-snouted profiles of other tyrannosaurs—and it was a close relative of the northern forms Daspletosaurus and Tyrannosaurus. Based on its anatomy and its geographic place, Teratophoneus appears to be part of a unique radiation of southern tyrannosaurs.

ティラノサウルスの化石は北米でも多く見つかっていますが、この時期の化石は、北部ではよく見つかっているのですが、南部ではあまり無かったそうです。今回は、同じ研究者が１年前に見つけた種に続いて、その空隙を埋める化石でもあります。 論文は下記。

Evidence for high taxonomic and morphologic tyrannosauroid diversity in the Late Cretaceous (Late Campanian) of the American Southwest and a new short-skulled tyrannosaurid from the Kaiparowits formation of Utah The fossil record of late Campanian tyrannosauroids of western North America has a geographic gap between the Northern Rocky Mountain Region (Montana, Alberta) and the Southwest (New Mexico, Utah). Until recently, diagnostic tyrannosauroids from the Southwest were unknown until the discovery of Bistahieversor sealeyi from the late Campanian of New Mexico. Here we describe an incomplete skull and postcranial skeleton of an unusual tyrannosaurid from the Kaiparowits Formation (Late Cretaceous) of Utah that represents a new genus and species, Teratophoneus curriei. Teratophoneus differs from other tyrannosauroids in having a short skull, as indicated by a short and steep maxilla, abrupt angle in the postorbital process of the jugal, laterally oriented paroccipital processes, short basicranium, and reduced number of teeth. Teratophoneus is the sister taxon of the Daspletosaurus + Tyrannosaurus clade and it is the most basal North American tyrannosaurine. The presence of Teratophoneus suggests that dinosaur faunas were regionally endemic in the west during the upper Campanian. The divergence in skull form seen in tyrannosaurines indicates that the skull in this clade had a wide range of adaptive morphotypes.