And sure enough, Nanotyrannus has juvenile bone and the bigger one has more mature bone.

There's the skull, pretty much the same shape as the Camarasaurus.

The bone histology tells us that Edmontosaurus is a juvenile, or at least a sub adult, and the other one is an adult and we have an ontogeny.

And if you cut into an older dinosaur, it's very massive.

And Torosaurus, when we cut into it, has mature bone.

So if we cut open Dracorex I cut open our Dracorex and look, it was spongy inside, really spongy inside.

228 million years old, we found what really is the most primitive dinosaur that's the Ur dinosaur.

Now as you can imagine, cutting open a leg bone is one thing, but when you go to a museum and say, You don't mind if I cut open your dinosaur's skull do you?

If you cut open Stygimoloch, it is doing the same thing.

And so she looked into the bone of this T. rex, one of the thigh bones, and she actually found some very interesting structures in there.

And I have been fortunate enough to find things like the first eggs in the Western hemisphere and the first baby dinosaurs in nests, the first dinosaur embryos and massive accumulations of bones.

And the little one is really spongy.

There's a kind of truncated Camarasaurus skeleton, but the geometry's correct.

Fossilized remnants of skin still cover the bumpy armor plates dotting the animal's skull.

This is one of my papers A pygostyle from a non avian theropod.

But cutting into the bones of a dinosaur is hard to do, as you can imagine, because in museums bones are precious.

But what was interesting was the adult Triceratops was also spongy.

So if you cut open a little dinosaur, it's very spongy inside like A.

So enormous excavations and a lot of work, and out of essentially a partial herd of dinosaurs that you saw buried there 20 tons of material we erect Jobaria, a sauropod dinosaur like we haven't seen on some other continents.

A three and a half foot thing, beautiful skull, predator, meat eater, a two legged animal.

But I have a museum and I collect dinosaurs and I can saw mine open.

If you look along the edge of the frill, they have these little triangular bones that actually grow big as triangles and then they flatten against the frill pretty much like the spikes do on the Pachycephalosaurs.

Dracorex is the littlest one, Stygimoloch is the middle size one, Pachycephalosaurus is the largest one.

We gave samples to Mary Schweitzer, and she was actually able to determine that B rex was a female based on medullary tissue found on the inside of the bone.

And I and my colleagues cut into it, and we were able to determine, by looking at lines of arrested growth, some lines in it, that B rex had died at the age of 16.

So there's these two dinosaurs, T. Rex and Nanotyrannus.

The fossilised remains of this particular specimen are so well preserved that remnants of skin still cover bumpy armour plates along the dinosaur's skull.

So, I went to the Museum of Natural History, and I checked out the bones, and I went to the gift shop, and I bought a book.

Chop, chop!

Which of course means that Stygimoloch and Dracorex are extinct.

Hey, hey, Lonesome. Lonesome boy. Hey.

Lonesome, nothing...

We now call them non avian dinosaurs and avian dinosaurs.

One moment. Fracture of the hyoid bone?

Luis Rangel was said to have suffered broken ribs and Inacio Nelson Guterres Amaral a broken arm.

And my skull's crushed and my collar bone is crushed all but two of my ribs, my pelvis and both arms they're all crushed, but there is still a pulse.

I mean, is there anything that is not visualizing what can't be seen, in terms of discovering this dinosaur bone from a small piece of it that's out there, or seeing the distortion that we try to see as evolutionary distortion in one animal to another?

Where are the baby dinosaurs? In a spellbinding talk from TEDxVancouver paleontologist Jack Horner describes how slicing open fossil skulls revealed a shocking secret about some of our most beloved dinosaurs.

We're not going to be able to make a dinosaur based on a dinosaur.

I mean, here's Edmontosaurus and Anatotitan.

It's a giant duck bill dinosaur.

The victim died as a result of the hyoid bone's fracture.

We began to find limb bones we found finger bones, the bones of the pelvis, vertebrae, ribs, the collar bones, things that had never, ever been seen before in Homo erectus.

You'd have a big dinosaur and a littler dinosaur.

Although the king of them all, Tyrannosaurus rex, lived millions of years after Borealopelta, the armoured dinosaur may have been hunted by some of its formidable ancestors.