[tool clinking] [soft music] - [Narrator] Bit by bit, paleontologists hope a 67-million-year-old mystery may finally be solved.

- [Lindsay] These particular specimens are even more fascinating than your average dinosaur.

- [Narrator] Scientists call them the Dueling Dinosaurs.

This is a model of the fossil, made up of two famous dinosaurs, the tyrannosaurus and triceratops.

And what's fascinating is that they were found intertwined, here in the Hell Creek Formation of Montana.

It's an arid moonscape now, but back in the Cretaceous Period when the dinosaurs roamed, it was an inland sea.

Researchers are drawn here by the wealth of fossils under its surface, including our Dueling Dinosaurs.

And that's the mystery.

Were the Dueling Dinosaurs actually dueling?

And why were they buried together?

And now they're at the NC Museum of Natural Science, where Dr. Lindsay Zanno and a team of researchers try to decipher this mysterious fossil.

They have their theories about how the pair may have wound up together.

- [Lindsay] That one day could have been fighting.

Maybe the triceratops was dead and a pack of these tyrannosaurus came in and they got angry at each other and one knocked one off.

Maybe a big flood or storm or a natural disaster killed them and then swept their bodies together.

- But they can't yet confirm any of these for sure.

What they do know is that there were several species of tyrannosaurus and triceratops from the Cretaceous Period living in the Hell Creek area at the time.

With the triceratops, they need to decide which one of the two or three species their skeleton could be.

But the tyrannosaurus leaves a larger question unanswered.

- It's just breathtaking, right?

It almost looks like it could just stand right up out of the rock.

This is almost the entire body of the tyrannosaur.

We've removed the skull, it's already under study.

We also have brand-new questions about tyrannosaurs that are part of longstanding controversies over what these small-bodied tyrannosaurs actually represent.

Are they juveniles of bigger species or are they just smaller bodied species of their own?

[pensive music] - [Narrator] And as they piece together the puzzle, they use a bit of science to piece together the bones.

The team uses reversible glue to reconnect the tyrannosaur to part of its hip.

- And the nice thing is if we discover other pieces and we need to take this piece off, I can just apply acetone back on there and it'll pop right back off.

- [Narrator] And these researchers use histology, the study of bone microstructure, to estimate how old the animal was when it died.

- So there's a lot of different things that you can tell from the bone microstructure, and that's why we actually will go ahead and cut some of the bones.

This block right here is the main body of our tyrannosaur.

You've got a beautiful articulated foot, so it's just like it would've been in the animal when it was alive, all the way down to these tips of the claws.

And you going up here to the ankle, then back to the shin, the femur, the upper bone would've been here.

We've got the hips there.

So that's what makes these animals so amazing is that they just have this beautiful articulation, again, just how it was in the body, and that can tell us a lot of information.

[soft music] - [Narrator] Beyond how they were found, these fossils are even more intriguing because there's more to the fossil than just the bone.

- [Lindsay] When you have an animal that was buried as a carcass with all of its soft tissue on, with its muscles and its organs, it gives you the opportunity to learn so much more about the biology of a dinosaur than you could if you just found its scattered, broken remains.

- [Narrator] It's a slow process.

Decay, fossilization, the waiting to be found.

And researchers have been, up until this year, patiently waiting to dig for answers.

- We've decided to make the process of science transparent to the public in a completely new way and invite people to come inside a real working science lab, talk to the scientific team every day about what's happening, and just experience it, the authenticity of being in a research environment.

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