IT’s an extraordinary discovery.

Palaeontologists digging in Hell Creek, Montana, have announced they’ve uncovered a the fossilised remains of a juvenile Tyrannosaurus Rex.

It’s one of the best preserved, and most complete, examples of a young T-Rex ever found.

The recovered fossils include the upper jaw — with all its teeth intact.

And they’re certainly not milk teeth.

Parts of its skull, backbone, hips and feet have also been found.

Their size and growth patterns indicate it was aged somewhere between 6 and eight years old when it died.

The fossil has been dated to some 66.5 million years ago. That’s prime Tyrannosaurus time.

But doubts linger as to its actual identity.

Some paleontologits argue young Tyrannosaurs are difficult to separate from another, smaller predator from the same era — Nanotyrannus.

Other palaeontologists argue Nanotyrannus doesn’t exist: they’re just gangly, awkward teen Tyrannosaurs before they’ve reached full growth.

“The teeth suggest it’s a Tyrannosaurus rex; however, there is still more work to be done,” says KU Biodiversity Institute researcher David Burnham.

At the heart of the problem is the process of growth. Proportions and shapes do not always remain exactly the same.

“Adult dinosaur bones, especially in the skull, don’t look the same as their younger selves. So, if someone finds a baby or juvenile fossil they may think it’s a new species, but we have to be careful since it may represent a younger growth stage of an existing species. It’s reasonable to assume Nanotyrannus could be valid — but we must show it’s not just a stage in the life history of T. rex.”

This well-preserved specimen providese the potential to solve the argument, once and for all.

“Because a young T. rex is so rare, there are only a few that have been found over the years, so it’s difficult to discern what are changes due to growth or if the differences in the bones reflect different species. Fortunately, KU has an older T. rex to compare with and another young T. rex on loan to help decipher this problem.”

The team that discovered the “baby” T.rex fossils hope to return to the same site in a few months in the hope of finding more of its bones preserved.

“We think and hope there’s more there,” Dr Burnham says.