At the twilight of the age of dinosaurs, an agile and vicious predator named Nanotyrannus prowled western North America, resembling a smaller version of Tyrannosaurus - about a tenth the body mass - but with several key anatomical differences.

For years, the "dueling dinosaurs" in a North Carolina museum were believed to be a Triceratops and Tyrannosaurus rex. However, an article published on October 30 in the journal Nature has a different take: The researchers believe that the T.

Paleontologists have long debated whether small tyrannosaurs were their own species or simply teenage T. rexes. This debate just got a major shake-up.

Specifically, whether or not certain fossils found in Montana belonged to a young Tyrannosaurus rex or a completely separate, smaller species. Researchers at North Carolina State University and Ohio University now say they can settle the debate.

Fossil known as Nanotyrannus was full-grown predator that lived alongside Tyrannosaurus rex, study finds - Anadolu Ajansı

After decades of fierce debate, researchers say fossils once thought to be juvenile T. rex actually belong to a separate, sleeker species of tyrannosaur.