The new species of tyrannosaur, Lythronax argestes, found in southern Utah belongs to the same evolutionary branch as the famous Tyrannosaurus rex and can reveal the origins of T-rex, scientists say.    
Among tyrannosaurs, a group of small to large-bodied, bipedal carnivorous dinosaurs including T-rex that lived during the Jurassic and Cretaceous periods, Lythronax possesses several unique features, a short narrow snout with a wide back of the skull with forward-oriented eyes.

Previously, paleontologists thought this type of wide-skulled tyrannosaurid only appeared 70 million years ago, whereas Lythronax shows it had evolved at least 10 million years earlier.    

Lythronax lived on Laramidia, along the western shores of the great seaway that separated North America; this landmass hosted a vast array of unique dinosaur species and served as the crucible of evolution for iconic dinosaur groups such as the horned and duck billed dinosaurs.

The study led by Mark Loewen, from the University of Utah also indicates that tyrannosaurid dinosaurs likely evolved in isolation on this island continent.

Lythronax stands out from its contemporaries in having a much wider skull at the eyes and a narrow short snout, similar to its relative T-rex, which lived 10 to 12 million years later.

"The width of the back of the skull of Lythronax allowed it to see with an overlapping field of view, giving it the binocular vision, very useful for a predator and a condition we associate with T-rex," said Mark Loewen, the study's lead author.

Lythronax and its tyrannosaurid relatives on southern Laramidia are more closely related to each other than the long snouted forms from northern Laramidia.


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