Scientists reassessing a partial skull first unearthed in 1983 in southeastern New Mexico have concluded that the fossil represents a new species of Tyrannosaurus - the fearsome apex predator from western North America at the twilight of the dinosaur age - that predated the fabulously famous T. rex.
Subtle differences from Tyrannosaurus rex observed in the skull merit recognizing the dinosaur as a separate species called Tyrannosaurus mcraeensis that lived several million years before T. rex and was comparable in size, the researchers said on Thursday. The skull previously was identified as a T. rex.
Other researchers expressed doubt that it represents a new Tyrannosaurus species, saying differences between it and other T. rex skulls were unremarkable and the study's conclusion that the fossil dated to 71-73 million years ago was problematic.
