How do scientists know that a fossil fragment they found belongs to an already existing dinosaur and not a new species?

Question

Say when a scientist discovers a new skull fragment from a T-Rex, how do they know it’s a skull fragment from a T-Rex and not like a fragment of some unknown species of dinosaur?

In: Biology

Answer 1

It’s very hard to tell with just a fragment. Even when you have most of a skeleton there can be questions. Considerable debate exists today on whether micro-tyrannosaurus is a different species or just the juvenile T-Rex form.