Genus of tyrannosaurid dinosaur from the Late Cretaceous period
Lythronax
Temporal range: Late Cretaceous, 81.9–81.5 Ma
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Reconstructed skeleton, Milwaukee Public Museum
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Clade:
Dinosauria
Clade:
Saurischia
Clade:
Theropoda
Family:
†Tyrannosauridae
Subfamily:
†Tyrannosaurinae
Clade:
†Teratophoneini
Genus:
†Lythronax Loewen et al., 2013
Type species
†Lythronax argestes
Loewen et al., 2013
Lythronax (LYE-thro-nax) 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 5 and 8 m (16 and 26 ft) in length, and between 0.5 and 2.5 t (1,100 and 5,500 lb) 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 maxilla bone of the upper jaw; most tyrannosaurids had more. The frontmost teeth were the largest, the longest being almost 13 cm (5 in) 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 astragalus of the ankle, a projection that expanded further upwards compared to its relatives.
The holotype was found in the Reynolds Point Member of the Wahweap Formation, which dates to the Campanian stage of the Cretaceous. Lythronax is thus the oldest known member of the family Tyrannosauridae, and it is thought to have been more basal than Tyrannosaurus. Due to its age, Lythronax is important for understanding the evolutionary origins of tyrannosaurids, including the development of their anatomical specializations. The forward-facing eyes of Lythronax gave it depth perception, which may have been useful during pursuit or ambush predation.
Lythronax (LYE-thro-nax) is a genus of tyrannosaurid dinosaur that lived in North America around 81.9-81.5 million years ago during the Late Cretaceous...
comparison. This subfamily also includes the oldest known tyrannosaurid genus Lythronax as well as the youngest and most famous member of the group, Tyrannosaurus...
C. Dooley, Jr. Dynamoterror was closely related to Teratophoneus and Lythronax. In August 2012, a partial skeleton of a tyrannosaurid was discovered...
unique row of bony bumps along the top of their snouts. The discovery of Lythronax argestes, a much earlier tyrannosaurine, further reveals the close relationship...
than Teratophoneus, but less derived than Lythronax. It forms the sister taxon of a group that includes Lythronax, Nanuqsaurus, Tyrannosaurus, Tarbosaurus...
tons). In 2021, based on the size of the frontal bone (similar to that of Lythronax), Yun moderated the size of the subadult at approximately 6.1 m (20 ft)...
to be the sister taxon of T. rex. The discovery of the tyrannosaurid Lythronax further indicates that Tarbosaurus and Tyrannosaurus are closely related...
phylogenetic analysis published with the description of the tyrannosaurine Lythronax in the journal PLOS One by Loewen et al. 2013, recovered Zhuchengtyrannus...
hutchisoni, unnamed ankylosaurs and pachycephalosaurs, and the theropod Lythronax argestes, which was likely the apex predator in its ecosystem. Vertebrates...
remains of a tyrannosaurid theropod were found at the site. The tyrannosaur Lythronax is known from the Middle Member of the Wahweap Formation, but the remains...
Tyrannosauridae, with the clade of Bistahieversor and the clade formed by Lythronax and Teratophoneus living in the south of Laramidia, and Albertosaurinae...
Diabloceratops eatoni, unnamed ankylosaurs and pachycephalosaurs, and the theropod Lythronax argestes, which was likely the apex predator in its ecosystem. Vertebrates...
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