What a Dinosaur Looks Like Under a Microscope

Hey I'm Kallie Moore We're here at the Museum of the Rockies in Bozeman, Montana to interview an amazing paleontologist.

Ha!

I recently travelled to Hoth, I mean uh Bozeman Montana to meet with some of my colleagues in paleontology.

And my first visit was to the paleohistology lab at the Museum of the Rockies.

There, Dr. Ellen-Terese Lamm explores ancient life by studying it at the cellular level.

I met with her to talk about how she does this, and what she's learned by putting dinosaur bones under a microscope.

So let's just jump right in.

What is histology and what is paleohistology?

Histology is the study of the microscopic structure of biological tissues.

And in paleohistology, we study the microscopic structure of fossil remains.

Paleohistology is essentially used as a tool within paleontology to answer deeper questions about dinosaurs and other ancient life on earth.

We can answer questions about dinosaur growth.

About dinosaur behavior.

About the individual health of the animal.

We can look at a whole growth series An ontogenetic series And get an idea of the physiology going on with that animal group and how fast they grew Something like a line of rested growth, counting those can let us know the chronological age of the animal What?

So you can tell old some of these animals were when they died?

Yes Oh my gosh.

That's crazy.

What's the oldest individual?

The oldest individual...Well I would say probably 30 plus - -that's not too bad- for one of the larger sauropod dinosaurs wow and then with other fossilized remains such as ossified tendons we can understand dinosaur posture better and biomechanics So ossified tendons fossilized nicely and they're found along the spine of the dinosaur and now we understand that dinosaurs are not dragging their tails around.

That they're holding them erect Which seems obvious because there's no tail drag marks in between dinosaur footprints There you go.

Very good.

So your whole process starts with a thin section.

Correct?

What is a thin section?

To produce a thin section slide, we take a fossil bone.

We'll embed a small portion of it in resin and we'll cut very thin wafers.

Those wafers are mounted onto glass slides, ground even thinner, until it's thin enough for light to transmit through and for us to see the structure underneath the microscope.

So a thin section slide ends up being about 100 micron thin slice of fossil bone that's been stabilized and secured onto a glass slide.

One project Dr. Lamm is working on is a study of how Tyrannosaurus rex grew throughout its lifetime.

To get the closest possible look at the tyrant king, she's prepared the tibia, or lower leg bone, of a T. rex found in western Montana, to put under a microscope.

So right here, is um, tyrannosaurus rex.

This is part of a t. rex growth study.

After our first cut is made on saws, so we'll take it to the saw, we'll expose the bone inside, and then this enables us to cut a thin wafer of bone and have it be stabilized on the open end and then exposed here.

And then we will mount that onto a glass slide and then I spend many hours at the lapidary grinder.

Generally listening to books on tape.

Until we get that 100 micron thin wafer of bone.

It's so pretty.

Yes.

Oh my goodness.

It's beautiful here and it's exquisite under the microscope.

The science and the art are all blended together once we're there.

What do you look for in a bone to be a good candidate for thin sectioning?

When we produce thin section slides, We are choosing specimens based on a question that we're asking or a hypothesis that we're testing And the next bone on the chopping block is going to maybe fill in a piece of the puzzle.

So you might have something missing in an ontogenetic series.

So really good candidates for that project is if you can find an animal at that stage of growth to add in.

Generally what we see in hard tissue histology and paleohistology is the work that the cells did while they were alive.

So we know how a bone grows.

We know we begin with calcified cartilage that will form into primary bone and then mature into secondary bone and then eventually develop into something called dense haversian bone.

So each of those stages of growth have different kinds of tissue that are evident.

So this one here is a tyrannosaurus rex.

Metatarsal bone.

So that's in the foot?

The foot.

What we see here is the beginning of dense haversian bone.

And these circular structures are called osteons.

And so you got to think in 3D this is a transverse section of the bone.

So these are actually long columns of bone with a vascular canal.

Surrounded by concentric rings of bone.

And the small little dots that you see, those are osteocyte lacunae.

So each of those held one bone cell.

And it's really a brilliant design.

It's the way that the body gets into our skeleton and uses the mineral matrix to drive physiology.

Maybe heal another energy.

So the amount of erosion and redeposition can also let us know about the health of the animal or how far it is into it's maturity.

So all of that's in there.

That's crazy.

And more.

There's just so much stuff in bone.

One of the most striking discoveries that Lamm has made occured when she studied the remains of baby Maiasaura, duck-billed dinosaurs that lived in Montana more than 70 million years ago.

Her research into the animals' growth ended up changing much of what we thought about dinosaur behavior.

So when I first arrived, we were completing the maiasaur growth series and what was found was in the nesting locality, that the very young nestling maiasaur had incompletely formed ends of their long bones.

So we're seeing here preserved is calcified cartilage and the orange band in the middle.

That's a little spicule of primary bone just beginning to form.

So along the edges you can see how bone actually uses what was left behind by the calcified cartilage as the scaffolding to build the primary bone on.

So this really provided great evidence for the idea of parental care being required for these animals.

They couldn't hatch out and run around.

Run around.

So hence maia, the good mother lizard was born and dinosaurs really shifted in what we saw them as far as taking care of their young, traveling in large family groups.

So that was right to the behavior of the young as well as the adults.

And made the whole area make more sense because in that nesting ground outside Choteau, Montana, there are all ages of maiasaura together.

Ages and stages all the way up from embryonic bone to hatchling, nestling, juvenile, sub-adults, adults, all the way up.

Are there any resources for people that want to check this stuff out in a little closer detail?

A website?

Excellent.

We have a lab website and we've got a google map up with about 60 different projects that we've done around the world.

So you'll click on the pin and it'll tell you what we cut in Mongolia and what researcher and institution we were working with.

So we've sectioned material from all 7 continents.

And everywhere around the world.

That's amazing.

You can see who a lot of our collaborators are as well.

And then a link to our book, bone histology of fossil tetrapods.

And that is an excellent resource that will cover I was flipping through it man and that is a really neat.

It belongs on my bookshelf.

Excellent.

I will sign a copy for you.

Yes!

Thanks so much for having us here today.

You're very welcome.

This has been amazing.

Mind-boggling.

Awesome.

Thanks so much.

Thank you for coming.

It was great to have this discussion with you.