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.

A new look at the "Dueling Dinosaurs" fossil reveals that Tyrannosaurus rex was not the only tyrannosaur roaming the land.

"The fossil, part of the legendary 'Dueling Dinosaurs' specimen unearthed in Montana, contains two dinosaurs locked in prehistoric combat: a Triceratops and a small-bodied tyrannosaur. That tyrannosaur is now confirmed to be a fully grown Nanotyrannus lancensis – not a teenage T. rex, as many scientists once believed," the release continued.

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

The “dueling dinosaur” fossil still leaves more questions than answers as scientists now attempt to determine their causes of death and why they were so perfectly encased mid-battle.

For many years, paleontologists have debated about whether there was a smaller relative of the Tyrannosaurus rex, or if those smaller fossils were really just awkward teenage versions of the king of dinosaurs.

Governor Josh Stein, the North Carolina Museum of Natural Sciences and NC State University announced Thursday that the species, Nanotyrannus lancensis, has been definitively identified in the museum’s “Dueling Dinosaurs” fossil, overturning a long-held belief that the specimen was simply a juvenile T. rex.

Researchers say they have uncovered a case of mistaken identity and found evidence of a species called Nanotyrannus lancensis.

Scientists have unveiled Khankhuuluu, a new Mongolian dinosaur species that predates and closely resembles early Tyrannosaurs. With its long snout, small horns, and lean build, it represents a transitional form between swift mid-sized predators and giant apex hunters like T.