Paleontologists may have unearthed a fossil of a baby Tyrannosaurus rex from the Hell Creek Formation in central Montana.
The remains include the upper jaw with all the teeth intact. Parts of the dinosaur's skull, hips, and backbones were also found.
The teeth suggest the fossils were remains of a Tyrannosaurus rex that lived about 66.5 million years. It also looked like the fossil belonged to a juvenile, but researchers said that there is still more work to be done to confirm this. The fossil could have belonged to another species of small and carnivorous dinosaur.
Remains Could Be Of A Baby T-Rex Or Another Species Of Dinosaur
David Burnham, from Biodiversity Institute of The University of Kansas said it is rare to find remains of a young T. rex, and there are actually only a few that have been found so far.
This makes it difficult for researchers to identify changes in the prehistoric animal that are caused by growth. It makes possible that observed differences in the bones of the specimen and those of adult Tyrannosaurus rex could mean the fossil belonged to a different species.
"It's reasonable to assume Nanotyrannus could be valid — but we must show it's not just a stage in the life history of T. rex," Burnham said.
The researcher said that the confusing issue with the find is the dinosaur's age, citing that the bones of adult dinosaurs, particularly the skull, do not look the same as when they were younger. He said it is possible that the specimen belonged to Nanotyrannus, a carnivorous dinosaur that was also found in the Hell Creek Formation.
The Nanotyrannus is also a controversial dinosaur species because it isn't clear if it represents a separate species or if it is just a young Tyrannosaurus rex.
In 1988, paleontologist Robert Bakker and colleagues announced that the fossil of the so-called Cleveland skull, which was unearthed in 1942 and housed in the Cleveland Museum of Natural History collections for decades, belonged to a new genus of small-bodied tyrannosaur. They called this Nanotyrannus.
Other scientists, including Carthage College paleontologist Thomas Carr, however, think otherwise. At the 2015 Society of Vertebrate Paleontology meeting, Carr and colleagues proposed that Nanotyrannus is just the younger version of the Tyrannosaurus rex.
"The extreme changes from the sleek skull of juveniles to the robust skull of adults were too much for some people to believe," Carr said. "For example, they didn't like to hear that T. rex lost tooth positions as it grew from a juvenile with many teeth, to an adult with fewer teeth."