Behold Siats meekerorum, one of the largest terrestrial apex predators ever discovered. Paleontologists think it may have been bigger than even the almighty T. rex, holding it back on the evolutionary food chain for millions of years.


The Cretaceous-era dinosaur, whose moniker stands for "Man-Eating Monster," may be the biggest carnivore to have ever terrorized North America (it was named according to Ute legends, a native tribe of Utah). This carcharodontosaur, known for their jagged, sharp teeth, lived approximately 98 million years ago. It's the earliest allosauroid theropod yet discovered in North America.

Image: Julio Lacerda


The recently discovered specimen was a juvenile, but even conservative estimates place it at 30 feet (9 m) long and weighing — wait for it — an astounding 9,000 pounds (4,082 kg).

Julio Lacerda from Discovery News tells us more:

"Siats still had a lot of room to grow, and there is only a 4-inch difference between the estimated femur length of a juvenile Siats and an adult Acrocanthosaurus (the second largest predator in North America), so we think a safe estimate for an adult Siats is that it at least vied with Acrocanthosaurus (11,000 pounds) for the No. 2 slot," lead author Lindsay Zanno told Discovery News. "However, our upper estimate on Siats is a body mass larger than T. rex (currently in the No. 1 spot), so future material may reveal Siats grew up to be one of the biggest predators known around the globe," added Zanno, who is director of the Paleontology and Geology Research Laboratory at the North Carolina Museum of Natural Sciences.

Interestingly, the paleontologists who conducted the study, Lindsay Zanno and Peter Makovicky, theorize that Siats (pronounced see-atch) prevented proto-species of T. rex from evolving into even larger dinosaurs.

Image: Jorge Gonzalez


It wasn't until this apex predator left the scene that an ecological niche was opened for tyrannosaurs. In fact, the scientists even think that Siats may have preyed on early evolutionary version of T. rex.

Read the entire study at Nature.