Now, a research team says new evidence resolves the case. The latest clue comes from a complete skeleton — first uncovered in Montana in 2006 — that scientists say identifies the mystery reptile as its own species and not a juvenile Tyrannosaurus rex.

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

Now a research team said there’s new evidence that resolves the case. The latest clue comes from a complete skeleton — first uncovered in 2006 in Montana — that scientists say identifies the mystery reptile as its own species and not a juvenile Tyrannosaurus rex.

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.

There are literally decades of research... based on a premise that this article overturns,” said one paleontologist.

An argument over whether fossils from several small dinosaurs represent a juvenile Tyrannosaurus rex or smaller adults of a separate species may finally be settled.

Paleontologists in North Carolina say they have evidence that a tyrannosaur species coexisted with T. rex, a speedy and agile creature called Nanotyrannus. "This fossil doesn't just settle the debate.