Lythronax

Lythronax () is a genus of tyrannosaurid dinosaur that lived in North America around 81.9-81.5 million years ago during the Late Cretaceous period. The only known specimen was discovered in Utah in the Wahweap Formation of the Grand Staircase–Escalante National Monument in 2009, and it consists of a partial skull and skeleton. In 2013, it became the basis of the new genus and species Lythronax argestes; the generic name Lythronax means "gore king", and the specific name argestes originates from the Greek poet Homer's name for the wind from the southwest, in reference to the specimen's geographic provenance in North America.

Size estimates for Lythronax have ranged between in length, and between in weight. It was a heavily built tyrannosaurid, and as a member of that group, it would have had small, two-fingered forelimbs, strong hindlimbs, and a very robust skull. The rear part of the skull of Lythronax appears to have been very broad, with eye sockets that faced forwards to a similar degree as seen in Tyrannosaurus. Lythronax had 11 tooth sockets in the of the upper jaw; most tyrannosaurids had more. The frontmost teeth were the largest, the longest being almost long. Other details of the skull and skeleton which distinguished Lythronax from other tyrannosaurids included the s-shaped outer margin of the maxilla and a process of the of the ankle, a projection that expanded further upwards compared to its relatives.