Lythronax

Lythronax is an extinct genus of tyrannosaurid theropod dinosaur which lived around 80.6 to 79.9 million years ago in what is now southern Utah. The generic name is derived from the Greek words lythron meaning "gore" and anax meaning "king". Lythronax was a large sized, moderately-built, ground-dwelling, bipedal carnivore, that could grow up to an estimated 8 m (26.2 ft) in length and weighed 2.5 tonnes (5,500 lb).

L. argestes is the oldest known tyrannosaurid, based on its stratigraphic position. It is known from a specimen thought to be from a single adult that consists of a mostly complete skull, both pubic bones, a tibia, fibula, and metatarsal II and IV from the left hindlimb, as well as an assortment of other bones. Its skull anatomy indicates that, like Tyrannosaurus, Lythronax had both eyes facing the front, giving it depth perception.

Etymology
Lythronax was named for its likeness to Tyrannosaurus. Loewen et al. wanted to symbolize that the fossil was alike in most features to the much later tyrannosaurid. They decided to keep the 'king' in the name and without using 'rex', named it Lythronax, the "Gore King", accordingly. For the specific name they agreed to have argestes, relating to the area where the fossil was found, southwest Utah.[1][2] The generic name is derived from Greek λύθρον, lythron, 'gore' and ἄναξ, anax, 'king'. The specific name is the Greek ἀργεστής, "clearing", used by the poet Homer as the epithet of the southwind.

Description
It has been estimated that Lythronax would have been about 7.3 m (24.0 ft) long, with a weight of around 2.5 tonnes (5,500 lb), based on comparisons to close relatives, and had a large skull filled with sharp teeth.[2][3] The rostrum of its skull is comparatively short, since it makes up less than two thirds of the total skull length. The whole skull is very broad, and is only about 2.5 times as long as it is wide. Overall, the skull is morphologically most similar to that of Tyrannosaurus and Tarbosaurus. Its robust maxilla possessed a heterodont dentition, as its first five teeth are a lot larger than the other six. Like other tyrannosaurids, Lythronax has large, distally expanded pubic boot which is approximately 60% the length of the pubic bone. The postcranial morphology is similar to that of other tyrannosaurids.