New Dinosaur Changes Understanding of T. rex Origins
by Brian Switek
Named Lythronax argestes in a PLoS One study by Natural History Museum of Utah paleontologist Mark Loewen and colleagues, the 23 foot long tyrannosaur lived about 12 million years before Tyrannosaurus and trod a part of southern Utah that laid near the coast of a long-lost subcontinent called Laramidia. The pieces of skull and postcrania were discovered within the vast wilderness of Grand Staircase-Escalante National Monument. Yet, despite the distance in space and time, the skull of Lythronax holds a remarkable resemblance to Tyrannosaurus.
Rather than having a narrow, streamlined skull typical of later tyrannosaurid dinosaurs found further to the north – such as Gorgosaurus and Daspletosaurus – Lythronax shared with Tyrannosaurus a skull that widened towards the back, giving these carnivores extra room for powerful jaw muscles and having the added benefit of situating their eyes to the side far enough to allow for binocular vision. Lythronax was one of the few predatory dinosaurs that could have stared you down.
But it would be a mistake to call Lythronax an ancestor of Tyrannosaurus. As study co-author and NHMU paleontology curator Randall Irmis commented at a press conference about the dinosaur this morning, Lythronax was more of a “great uncle” to Tyrannosaurus than an ancestor. Loewen put it another way – the ancestor of Tyrannosaurus is also the ancestor of Lythronax, meaning that these two predators represent close lineages that split from an even earlier common ancestor.
This is why Lythrnoax is so strange. The 80 million year old dinosaur was among the first of the famous tyrannosaurid group, yet it looks very much like one of the very last of the tyrannosaurids. This suggests that are even more tyrannosaurs waiting to be found…
(read more: Laelaps blog - National Geo)
images: illustrations by by Lukas Panzarin (T) & Scott Hartman (ML) via Mark Leowen, and Andrey Atuchin (B)