to see a bit of Sue's blood vessels.

Jasmina Wiemann: Yes. Abby: That's rad.

Jasmina: And you're going to be the second.

[Abby laughs]

It's this hollow

branching shape. Abby: Yes, yeah!

That Sue in question is Sue the T. rex,

and we're about to see proof that she was warm-blooded.

We went to the Field Museum

to see how they work their magic.

Our first stop was ...

So, here is our dinosaur and oversize collections.

Abby: That's Jingmai O'Connor, and she --

you know what? I'll let her tell you.

Yeah, I would say I'm one of

the world's experts on Mesozoic birds.

Not to brag or anything. Nah, I'm just kidding.

Abby: And one of the key questions she asks

with her research is why birds were the only dinosaurs

to survive the Cretaceous-Paleogene extinction.

We need to look at birds,

and then we need to back up from birds

and look at the dinosaurs closely related.

I think it's kind of funny,

but we have a drawer full of bits of Sue.

When you have the edge of the puzzle,

that's the easiest part to do, right?

The inside of the puzzle is harder to put together.

So these are like the inside puzzle bits.

You can't figure out where they go,

but this is to our advantage,

because these are the type of fragments

that it's OK for us to do destructive analyses on.

Abby: The destruction of these rare

and one-of-a-kind fossils

can involve slicing or dissolving in acid.

Slicing allows the scientists

to study specimens histologically.

You have to cut a piece of the bone, remove it,

grind it down so it's really thin

so that light can pass through it

so you can study it under a microscope.

It's a cost-benefit analysis essentially, right?

What are the questions you're trying to answer?

Is it worth it to damage

this extremely rare, important fossil?

Abby: To show me how it's done,

they demonstrated with a prehistoric bird bone.

Jingmai: You're going to bring it to,

in our case, Akiko Shinya.

She's our chief fossil preparator.

She's amazing.

Abby: Akiko starts by taking

a small slice of the specimen.

Jingmai: You then take your little chunk of bone

that you've removed, and you drop it into resin.

And then this needs to cure for several days.

I mean, can you imagine playing Dungeons and Dragons

with dinosaur dice? Abby: Dungeons and Dinosaurs.

Oh!

Exactly.

Abby: Then you glue your D6 to a microscope slide

and slice it down even more.

I did a terrible job with the saw.

I almost destroyed everything with the saw, actually.

I feel like I'm pushing too hard.

Akiko: It's OK. Abby: OK.

[yelps]

I did it.

Abby: At this point, it's too small to slice,

so Akiko will grind away extra layers.

Abby: We're listening for that "shoog-shoog" sound.

[shoog-shooging]

The slide ultimately needs to be between

30 and 80 microns thick --

thinner than a sheet of paper.

Akiko basically uses finer and finer grinders,

like varying grades of sandpaper,

to slowly shave off extra layers.

Akiko: Straight down. That's the key.

Abby: I will try my best. Akiko: Yeah, I'll show you.

Abby: You scared me now, though.

There's a polishing stage to smooth out

any major imperfections that might obstruct the sample.

You're not getting away from me!

And a second polish for fine tuning.

This one feels like someone is

pulling carpet out from underneath the block.

Even with your naked eye, you can learn about a specimen.

Here's a piece of Sue's rib,

and you can see how Sue grew

almost like rings on a tree.

You see these faint lines?

Yeah.

Jingmai: Yeah, it'll be much -- Abby: It looks like agate.

Yeah, it'll be much clearer

once we get it under a microscope,

but those are the lines of arrested growth.

Do you want to look in?

Jingmai: And here we're looking into

the rib of Sue the T. rex.

You notice that the space between these lines of growth

is becoming smaller and smaller.

So when it was younger and really having to bulk up, right,

it was growing very quickly.

And as it reaches adult size, growth slows down.

Abby: The thinness of these sections was surprising

because it shows a fast growth rate,

a key indicator that Sue had a high metabolic rate,

meaning she was probably not as cold-blooded

as scientists previously thought.

Scientists also looked at another indicator

of high metabolism, which is actually color.

More diverse colors in a species

tends to mean a higher metabolism.

Jingmai: Here, we are looking at an SEM image

of a sample from a feather

of a 130-million-year-old bird

called Eoconfuciusornis.

Abby: Pre-extinction.

Jingmai: So the only fossil bird

older than this fossil bird is Archaeopteryx.

Abby: A scanning electron microscope relies on

electrons instead of light to magnify even more detail.

Jingmai: And so if you look closely, you'll see these --

this is literally what we call them --

sausage-looking structures.

[Abby laughs]

They are eomelanosomes.

So eomelanosomes are responsible for the color black.

Abby: Melanosomes are organelles found in animal cells

that are associated with different colors.

When they fossilize, they leave behind distinct shapes.

Jingmai: If they're very nicely aligned with each other,

we can tell it's iridescent black.

If they're kind of a more oval-shaped eomelanosomes,

that's gray, and then if it's a phaeomelanosome,

we call these ones meatballs.

Literally, this is like,

in papers, they're like, Abby: Such a delicious science.

"the meatball-shaped ones."

Like, mm, I'm hungry.

The meatball-shaped phaeomelanosomes are responsible

for a rusty red color.

Abby: Many of the genes responsible for melanosomes

are also linked to things that affect metabolism,

so evolving one most likely evolves the other.

And with both meatballs and sausages,

Eoconfuciusornis shows way more melanosome size diversity

than modern-day cold-blooded lizards.

Jingmai: So we can say that the dinosaurs

that are becoming smaller, that are getting

these large extravagant ornamental structures

that are then able to evolve flight

are also becoming more colorful.

Abby: But these melanosomes can only tell us so much.

They're an indicator of warm-bloodedness,

but not definitive proof.

This is where Jasmina comes in.

Jingmai: Everything that Jasmina is doing,

five years ago that didn't exist.

I'm a molecular paleobiologist.

My passion lies within

the clade of dinosaurs including modern birds.

People tend to think of bones and shells

and these kind of heart tissues

that preserve much more readily.

But if we want to get a complete picture

about the diversity of life on our planet,

we really depend on soft-tissue preservation.

Abby: Soft tissue is the squishy stuff like skin,

blood vessels, and other non-bony materials

that scientists didn't even think

could preserve until recently.

So, about 30 years ago,

a vertebrate paleontologist tried for the first time

to extract soft tissues from dinosaur heart tissues.

Abby: Her name is Mary Schweitzer,

and people did not believe her findings.

It was very critically perceived,

and people thought for a long time

that while these soft-tissue structures

very much looked like the original biological structures,

they could not possibly be related.

Abby: But soft tissues do preserve.

Why do they preserve?

This is absolutely paradoxical

based on what was known scientifically

at that point in time.

Abby: You can actually see traces of it under a UV light.

Jingmai: What we're going to do is just shine the light

and look for things.

It looks like some of these may be scales

that are preserving soft tissue.

Not all of them.

Abby: Once soft tissues are suspected,

demineralization will isolate them if they're present,

so you can see the structures.

This is where I got to try something with Sue's bones

that has never been done before.

So, you mentioned that you would like to dissolve

a Sue fragment and help us look for organics.

Every bone is going to have

the tissues that we're looking for

if they are in fact preserved.

But Sue has exceptional preservation,

so we are quite hopeful.

Abby: We're taking this bit of Sue

and dissolving it in hydrochloric acid.

The acid will dissolve any inorganic rock

but leave behind the organic soft tissues.

It's starting to look like a hazy IPA.

Are you seeing anything?

Jasmina: It's all still in suspension.

Abby: Me too. Jasmina: We'll have to

give it a little bit of time.

Abby: After about 15 minutes,

the precipitate settles

and Jasmina pipettes it onto a slide.

Jasmina: From here we go to the microscope.

Abby: Let's go.

Jasmina: Ooh, this is looking good.

Abby: What are you seeing?

Jasmina: We have a couple of

extracellular matrix pieces,

blood vessels, large blood vessel fragments.

Abby: You are the first person to see

a bit of Sue's blood vessels.

Jasmina: Yes.

I was the second person

to see Sue the T. rex's veins.

Right now, take a look.

Abby: OK.

Jasmina: Do you see the blood vessel structures

right in the focus center?

It's this hollow

branching shape. Abby: Yes, yeah!

Jasmina: That is definitely one of the

bone vascular canals.

Abby: [gasps] Oh, I see it real good now.

Hold on.

They've just been in there the whole time!

Jasmina: They've been sitting there

for 65 million years. Abby: Just floating around.

[Abby laughs]

That was rad.

Because we can look at this

of course fascinated by the fact that,

you know, soft tissues preserve in the time,

but there's actually a lot of information

in the molecular composition

of these materials. Abby: Yeah, what can we see?

Demineralization shows us that

there are soft tissues present in a specimen,

including the proteins, lipids,

and sugars that indicate a high metabolism.

But to concretely say

what soft tissues are present

and prove that this vein is really a vein