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WEDNESDAY, Nov. 27, 2013 (HealthDay News) -- Scientists have identified a giant meat-eating dinosaur that roamed the Earth about 100 million years ago and was likely dominant over early tyrannosaurs.
The remains of the creature were found in the Cedar Mountain Formation in Utah. It is the first of its kind discovered in North America, the researchers said in a news release from the Field Museum of Natural History in Chicago.
"This dinosaur was a colossal predator second only to the great T. rex and perhaps Acrocanthosaurus in the North American fossil record," said study lead author Lindsay Zanno, director of paleontology at the North Carolina Museum of Natural Sciences and North Carolina State University.
The dinosaur -- named Siats meekerorum -- was more than 30 feet long and weighed more than four tons. Zanno initially discovered it in 2008 and its remains were retrieved during an excavation that lasted two summers.
The newly identified meat-eater was not a close relative of T. rex, but belongs to the family of predatory dinosaurs known as carcharodontosaurs. A famous member of that family is the Giganotosaurus, which was first discovered in Argentina.
Siats belongs to a branch of that family that was previously unknown in North America, according to the study, which was published in the Nov. 22 issue of the journal Nature Communications.
"We were thrilled to discover the first dinosaur of its kind in North America and add to mounting evidence that dinosaurs were widely dispersed across the globe 100 million years ago," study co-author Peter Makovicky, curator of dinosaurs at the Field Museum, said in the news release.
Siats appears in the middle of a 30-million-year gap in the fossil record of large predatory dinosaurs in North America. During that time, the top predator role changed from carcharodontosaurs in the Early Cretaceous period to tyrannosaurs in the Late Cretaceous period.
Teeth of tyrannosaurs from the Utah site indicate that the tyrannosaurs that were around at the same time as Siats were much smaller and did not compete for the top predator role.
"The huge size difference certainly suggests that tyrannosaurs were held in check by carcharodontosaurs, and only evolved into enormous apex predators after the carcharodontosaurs disappeared," Makovicky said.
"Finding Siats in the 30-million-year predator gap tells us carcharodontosaurs reigned supreme in North America for much longer than anyone had expected," Zanno said in the news release.
The Smithsonian National Museum of Natural History has more about dinosaurs.
SOURCE: The Field Museum of Natural History, news release, Nov. 22, 2013