Home Science & Technology Lythronax argestes: Oldest Tyrannosaurus rex discovered in Utah

Lythronax argestes: Oldest Tyrannosaurus rex discovered in Utah


A relative of the Tyrannosaurus rex has been unearthed in southern Utah, marking the discovery of the oldest known member of its group of dinosaurs yet.

The newly discovered dinosaur measured about 24 feet long, weighed around 2.5 metric tons, and had a large head filled with sharp teeth. To evoke just what a powerful predator it was, researchers have given it a fittingly grand name: Lythronax argestes, which translates to gore king of the Southwest.

The newly discovered dinosaur measured about 24 feet long, weighed around 2.5 metric tons, and had a large head filled with sharp teeth

The newly discovered dinosaur measured about 24 feet long, weighed around 2.5 metric tons, and had a large head filled with sharp teeth

The discovery is being reported this week in PLOS One by researchers led from the Natural History Museum of Utah. They describe the Lythronax as a two-legged carnivore with a short, narrow snout that lived around 80 million years ago. With the back of the Lythronax’s skull being on the wider side as well, the researchers note that it actually resembles the T. rex – which lived 10 to 12 million year later – more than any other dinosaur that lived alongside it.

“Lythronax may demonstrate that tyrannosaurs followed a pattern similar to what we see in other dinosaurs from this age, with different species living in the north and south at the same time,” Joseph Sertich, a co-author of the report, says in a statement.


Lythronax lived on the ancient continent of Laramidia, a split-off portion of North America that ran from Alaska, down the west coast of the US, and into Mexico. The researchers suggest that the sea that divided North America may also have spilled over into Laramidia, at times dividing its north and south and allowing dinosaur genera to divide into a variety of species. As for the recovered Lythronax fossils, the researchers will be keeping them close to home – they’ll be on display at the Natural History Museum of Utah in Salt Lake City as part of its permanent collection.

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