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Huge dino preceded T. Rex



Tyrannosaurs reign as the most famous of all meat-eating dinosaurs. But they didn’t always dominate, suggests the newly discovered bones of a massive carnivorous dinosaur that lived 98 million years ago.

Named Siats meekerorum (pronounced “See-atch”), the dinosaur discovered in eastern Utah by paleontologists was a previously unknown “apex,” or top, predator that ruled long before North America’s tyrannosaurs came to power.

In a recently published Nature Communications study, Lindsay Zanno of North Carolina State University and Peter Makovicky of Chicago’s Field Museum of Natural History add to our knowledge of gigantic dinosaur predators prior to the days of Tyrannosaurus rex, which lived some 67 million years ago.

At full size, the two-legged carnivore may have weighed more than four tons and stretched nearly the length of a school bus.

The discoverers report that the dinosaur’s first (or genus) name is a tribute to its predatory prowess. In the legends of Utah’s native Ute tribe, “Siats” is the name of a voracious monster.

Zanno knew she had discovered a significant dinosaur as soon as she happened across a collection of black bone fragments sitting on the surface of eastern Utah’s Cedar Mountain Formation.

Remains of large carnivorous dinosaurs are rare in these rocks. “We had no idea how much would be in the ground,” Zanno says, “but we were stoked because we knew immediately we had a larger theropod and that it was going to fill in a huge gap in our understanding of theropod evolution on the continent.”

The discovery team recovered a partial skeleton including vertebrae, parts of the hip, the lower leg, and toes.

At first, Zanno says, she expected that Siats would be something like the huge, sail-backed carnivore Acrocanthosaurus, but the new dinosaur turned out to be something else. Distinctive anatomic features on the bones mark Siats as a newly recognized type of predator called a neovenatorid, cousins of the earlier, well-known Allosaurus.