T. rex has company

"Meet the newly discovered dinosaur that even tyrannosaurs were afraid of"

 
by

Lance Tillson

November 23rd, 2013

National Monitor

Researchers from The Field Museum, the North Carolina Museum of Natural Sciences (NCMNS) and North Carolina State University (NCSU) note that the new dinosaur is the first of its kind to be found in North America.

More than 30 feet long and weighing more than four tons, Siats meekerorum was the top predator in its ecosystem.

“This dinosaur was a colossal predator second only to the great T. rex and perhaps Acrocanthosarus in the North American fossil record,” noted lead author Lindsay Zanno, Director of Paleontology at NCMNS/NCSU, in a statement.

The large predator was found in 2008 by Zanno during a trip to the Cedar Mountain Formation in Utah. It took two summers to remove the fossils of this giant animal.

According to the researchers, Siats is not a close relative of T. rex and other tyrannosaurs that were the prominent predators in North America for the last 20 million years of the age of dinosaurs. Siats belongs to the  carchardontosaurian group of theropods. Furthermore, the large predator belongs to a branch of the carcharodontosaurian family tree that was previously unknown in North America.

“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,” posited study co-author Peter Makovicky, Curator of Dinosaurs at the Field Museum.

The teeth of tyrannosaurs from the Cedar Mountain Formation suggest that the tyrannosaurs living alongside Siats were a lot smaller in size.

“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,” added Makovicky.

The study’s findings are described in detail in the journal Nature Communications.