Shaking the Dinosaur Family Tree

Shaking the Dinosaur Family Tree

Record date: Sep 21, 2017

David Lovelace, Museum Scientist in the Department of Geoscience at UW-Madison, shares findings from vertebrate paleontologists which shed new light on the biology and evolutionary history of dinosaurs.

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Episode Transcript

- Welcome, I'm Nicole

Perna, the Director of the

J. F. Crow Institute for

the Study of Evolution

and it's my sincere

pleasure to introduce

today's speaker, David Lovelace

from the UW Madison


David is a research

scientist at the museum,

but he's also involved with

a lot of outreach activities

there and for the Crow

Institute, in general.

I'm going to tell

you a little anecdote

about an activity I did

with David this past June

because it'll give

you some sense of

where he's coming from.

So, in late May, we got an email

from a middle school

teacher from Sun Prairie

asking us if we could

put together a panel

of four evolutionary biologists

to spend an entire day

with the middle school

biology classes, helping

to give them some feedback

and evaluate a

project they'd done

where the assignment was to

design a prehistoric park.

So, I said, "Sure. Why not?"

Because we hate to turn away

anybody that comes to us

asking for STEM education.

Lo and behold, we agreed and

then I hit send on the email,

and I thought, "Well,

where am I going to find

"four people with

about one week notice?"

So, I looked around, I started

quite literally at home,

signed up my husband and

figured I could apologize

for that later.

Then I looked around my lab

and I signed up my post-doc.

And then I said, "Well, three

evolutionary geneticists

"is not a real good

representation of

the whole breadth

"of evolutionary biology.

"We really need somebody

who knows something

"about fossils."

So I wrote to the geology museum

and they passed the

invitation along to David

and, within hours, he had

agreed to do this as well,

with really no more information

than what I've given you.

Flash forward a week and

we show up at the school,

and it turns out we are

literally going to listen to

five hours' worth

of presentations

from five different classes,

each of which has

been tasked to take

five transitional fossils,

assume they have DNA from it,

bring them back to life

and design a theme park.

And the students

spent several weeks

and came up with these

very elaborate plans.

So they had a team

dedicated to the research,

a team dedicated to

business and marketing,

a team dedicated to

educational outreach,

for each of the five classes.

And then a team

dedicated to building

these enormous,

three-dimensional models.

We walked in and there

were about five of these

large six-by-six models

complete with hotels

and enclosures and this,

that and the other thing.

Each class gave a

presentation and this panel,

which I would have

found intimidating

if I was in middle school,

sat there and asked them

a bunch of questions.

So the geneticists, we asked

kind of predictable questions,

things like, "What have you

done to ensure the safety

"of the animals?

Veterinary care and welfare

"of the park-goers?"

And they had good

answers to all that.

My husband Jeremy contributed

this important question,

"Why do soft

pretzels cost so much

"at the concession stand?"

(audience laughs)

But David had the

real meat of it

and I really admired

the way he very gently

brought the students around

to question their own design

in important areas, such as

"Well, you chose an

animal that's very small

"to be the surrogate

for this DNA

"but the animal

you're trying to grow

"is really, very large."

He would bring them around to

that realization on their own.

Along with that,

one very important,

maybe even the enduring

lesson from the whole thing,

is not all fossils

are dinosaurs.


And so, today David

will talk to us about

some actual dinosaurs

with his talk

Shaking the Dinosaur

Family Tree:

a New Look at an Old Story.

(audience applauds)

- All right, so how's

everybody doing today?

Awesome, so what I

want to talk about

centers on a paper that

came out earlier this Spring

by Baron and two colleagues.

It kind of revolutionized

the phylogeny of dinosaurs

and how we think about them.

What I want to do is

kind of go through,

first of all, the

history of dinosaurs.

Where'd they come

from, what are they?

And kind of walk

through that, talk about

the different clades, what we

know about them a little bit,

and then work into

this new hypothesis

that's been generated.

Within the vertebrate

paleontological community,

it's definitely

shaken things up.

And so, I don't know, you

may have caught it through

published in Nature and

there was quite a bit

of hub-bub around

it this Spring,

maybe it's quieted down

everywhere else except

my small community of

vertebrate paleontologists,

but we find it intriguing,

so we're going to

talk about that.

The story really

begins in the mid-1800s

and Richard Owen was the person

who coined the term dinosaur.

So, in 1841 he's the first

person to really coin it,

diagnose what a dinosaur

was and from that point,

you know this is

early in the history

of vertebrate paleontology,

and there are very few

specimens; all of

two at this point.

Shortly thereafter, in 1869,

so a decade after Origins,

Huxley, Darwin's bulldog,

Thomas Huxley came up

with the idea to unite

several of the major fossils

that had been found.

He was trying to understand

their evolutionary relationship.

He basically grouped together

everything that had been known

so it was kind of theropods

and Ornithischians,

and we'll talk about those.

He coined a term to basically

describe or characterize

that clade, the Ornithiscelida.

At that point, that's

what all dinosaurs were,

basically Ornithiscelidans.

That's where it ended

for a while until Seeley

came along and, in 1888,

he started looking

at these fossils.

At this point, remember,

most of the fossils

that had been collected

were actually from the

Jurassic or Cretaceous.

They're relatively derived.

Origins of dinosaurs runs

back around 220 million years

probably for the

common ancestor,

which of course we don't have,

but once you get into the

base of the family tree

right around 235-230

million years ago.

So most of these fossils were

almost a full 100 million

years younger,

relatively derived

and they had noticed

some characteristics.

Seeley was the person who

pointed out that there are

two major clusterings,

two major groups.

So, any time that you've had

probably dinosaur lectures

and people talking to

you about dinosaurs,

we talk about the Saurischia

and the Ornithischia.

So the Saurischia, here,

these are the sauropods,

these are the long neck,

long tail, super big ones.

You know, 12 tons

to 60-ton critters.

And then the theropods, of

course, the big meat-eating

and small meat-eating

dinosaurs that ultimately

lead to the rise of birds.

That's the Saurischians

and they are characterized

by their hips.

Both of these groups

are simply diagnosed

by their hip structure.

Specifically, of

the three hip bones,

the ischia faces backwards

and the pubis faces forward.

So it's an

anterior-facing pubis.

Whereas, the Ornithischians,

and so these are animals,

the Thyreophora, things

like stegosaurus,

or the armored

dinosaurs, Ankylosaurs,

and then Cerapoda,

things like Hadrosaurs

and Triceratops

and Ceratopsians.

They are faced with a

different hip structure

where their pubis and their

ischium face posteriorly.

That is the condition in birds,

hence the name ornith-ischian,

it's ischium like a bird.

But, the bird-hip dinosaurs,

as far as we've known

for over 140 years, did

not give rise to birds.

They are derived from the

lizard-hipped dinosaurs,

the Saurischia.

So there's been this kind

of dichotomous structure,

Saurischian and Ornithischian,

birds arrived from the one

that's not named for birds.

This has always been an

issue trying to figure out.

Basically we think

they secondarily

retroverted the pubis.

No big deal, right?

It's a bird, so it's

flexible character.

So we had this 100

years of evolution.

In 1870, old Waterhouse

Hawkins here,

he's in the crystal palace,

they've these

fantastic sculptures.

That was modern science in 1870.

This is what

Iguanodon looked like.

Notice the tip of his nose,

here, has a horn on it.

There's no horn there, that's

actually it's thumb spike.

So there's a lot of information

that they didn't know.

And this happens today,

dinosaurs that we describe

and mount today,

twenty years from now

somebody's going to

be looking at it,

laugh at us and say, "Oh

my gosh, how did they

"even possibly think this?" That's science, right?

This is the evolution

of our knowledge

and Iguanodon now is

seen as most dinosaurs,

as much more active, not this

lumbering colossal giant,

as much as this graceful

duck-billed dinosaur.

So when did this happen?

What gave rise to this

major shift 100 years later?

It really rises from this,

the work of Bob Bakker

and some of his Yale colleagues

in the 1960s and 70s,

they basically turned

over what they coined

"the dinosaur doldrums."

Pretty much, not a lot

happened during this.

You know, evolutionary

biologists were busy

with that whole new

synthesis thing.

I mean, there is a

lot of stuff going on,

so dinosaurs kind of

got pushed to the side.

And once they came up with

some of the new specimens,

specifically Deinonychus,

which is this

little theropod, meat-eating,

has a sickled claw,

looks like velociraptor, Bob

Bakker was working on that

saying, "You know, this thing

looks. I mean, it's a bird.

"Come on, look at this

thing, it is a bird."

Which goes back

to Huxley in 1870,

where he's saying, "Look,

birds probably arose

"from dinosaurs, they look

really, really similar."

But then that idea dropped

off for a long time.

So this reinvigoration

of the idea that they're

warm-blooded, and key to

this is that dinosaurs,

Ornithischians and Saurischians

shared a common ancestor.

Prior to this, for

the last 100 years,

they did not believe that

they shared a common ancestor,

that these were not

a monophyletic group,

as we would think of them today.

And they hypothesized

that these animals,

specifically the theropods,

gave rise to birds.

So it was kind of revolutionary.

It transformed the science

of vertebrate paleontology.

Basically this is

where we stood,

this was our understanding

of the dinosaur family tree.

You had these major clades,

they're monophyletic.

This is our knowledge, this

is the state of dinosaurs.

This is not all of

the dinosaurs we know,

but each one of these lines

that you can't see in there

is a genera and kind

of a silhouette outline

trying to show what they are.

That's the major tree.

We have, over on this side,

these round blobs are things

like Stegosaurs, right here.

Hadrosaurs, Ceratopsians.

And then we get

the theropod line,

and the sauropod line.

And what we're really

going to try to focus on

for much of this talk, I'll

explain the groups here,

but we're going to be

looking at the base

of the dinosaur family tree.

We're going to be looking

at the trunk down there.

To start with, down at the base,

we need to first figure out

where did dinosaurs come from.

What are they related to?

So, Archosaurs, is the major

clade that we're talking about

and all of those animals

include the Crocodylians,

the Crurotarsans and

the Crocodylomorphs

as a crown of that clade.

You have Pterosaurs,

so the winged reptiles,

the flying reptiles.

You have Proto-Dinosaurs,

the Dinosauromorphs

and then, true Dinosauria.

We're going to be focusing

on this part of the tree.

But, to start off with,

what are Archosaurs

and how are they differentiated

from the other animals?

The big thing here is

that, at this point in

the evolution of this group,

they go from this sprawling gate

of all other

reptiles at the time,

they go to a semi-erect posture,

they bring their

legs down under them,

they narrow their body plan,

they elongate it.

A lot of this seems

to be in response to

an increase in metabolism.

They're moving a

little bit faster,

they're doing more,

they're more active.

That increase in metabolic

heat requires them

to narrow their body to reduce

their profile effectively,

to shed heat, not

absorb so much heat.

So they're changing

at this point in time,

they're starting to evolve

into this kind of warm-blooded.

They interlock their

gastralia so they can breathe

with their ribs.

The Crurotarsi, these

are the Crocodylians,

and then we have

an extinct group,

Phytosaurs, which are

very similar ecologically,

set at the base of the

Crurotarsi and Crocodylians

at the crown.

Scleromochlus, this

is kind of cool,

so notice so far, everything

that we talk about

at the base of the

dinosaur family tree

is about this big.

So when we think dinosaurs,

most people think pretty big.

Right? Sauropods,

large theropods.

Most of the small stuff,

down at the base of the tree,

are very small.

Scleromochlus is probably

the ancestor of Pterosaurs,

which are a group

within Ornithodirans.

These are the flying reptiles

and they have very

small ancestors,

a lot of the first

ones are very small.

They'll also then get up

to be the size of Cessnas.

So it worked for them.

But, interestingly, most

of these that had flight,

certainly had

flight capabilities,

they were using those

big, springy legs

that we see in Scleromochlus,

they had these huge

things, they think they're

saltatorial, they were bouncing.

They actually use that

bounce to become airborne.

So these large, huge

things like Quetzalcoatlus

are probably launching

from the ground,

not flapping their wings

to get up into the air.

So there's some interesting

characters that we're looking

at the base of the tree,

they're very long-legged,

very long-armed

and the earliest dinosaurs,

whenever you look

at their skeletal structure,

look very similar to the


true dinosaurs,

except in the pelvis.

One of the defining

characteristics of dinosaurs,

here you go, here's the

million dollar thing,

when somebody says,

"What's a dinosaur?"

You can say, "any animal that

has a perforated acetabulum!"

(audience laughs)

If you have a hole in your

hip, you're a dinosaur.

Birds have a hole in their hip,

so, right, they're dinosaurs. Hey, cool.

The typical mammal

structure in many reptiles,

the head of the femur is a ball,

and it sits in the socket

and that's the hip joint,

within dinosaurs, that

perforated acetabulum,

that hole, meant that

the hook of the femur,

the femoral head,

would sit inside of it

and the ilium would

rest right on top of it.

That was their motion.

Now, one of the

advantages of that

is it locks the leg in to

an anterior-posterior motion

very well.

It gives you a lot of

structural stability

whenever you go to

being truly bipedal

and you weigh a lot.

The problem is that they

can't do the splits.

Well, they can, but they

can only do it once.

(audience laughs)

So there are some

limitations to this.

But there are some

distinct advantages,

and one of which is ...

This is my favorite dance,

you know, going to any

grade school, doing outreach,

talk about how reptiles breathe

and doing the back

and forth motion.

Dinosaurs didn't do that,

so it's not nearly so fun to

pretend to be a dinosaur

walking around, except

you get to stomp,

but you don't get this

awesome side motion.

Part of that is the

locking of the hips

and the upright

structure of the body.

So what is a dinosaur?

Just that it has this

perforated acetabulum,

and it has this

hinged ankle joint,

which differentiates it from

the Crurotarsan condition

where the ankle joint

actually is mobile

around the calcaneum,

as opposed to the calcaneum being introduced

into the ankle joint

itself within Dinosauria.

So, major groups.

We've talked about


and basically, we'll look

at the three major groups

of dinosaurs.

We have the Ornithischians,

these are the classic view,

these are the Ceratopsians here,

these are the armored

dinosaurs over here,

like the Stegosaurs

and Ankylosaurs,

and then all the duck-billed

dinosaurs on down.

So Ornithischians, one of the

things we'll be looking at,

at least in part, is really

low down in the tree,

is this critter Pisanosaurus.

It's a relatively

incomplete skeleton,

but it's got enough

material there,

certainly in the cranium,

to try to figure out

where this animal goes.

But it's this guy.

This is one of the major

ones that's kind of

messing with the tree.

You can imagine, as you get

down to the base of a tree,

there's a lot of problems

trying to distinguish groups.

That's where all

the trouble lies.

We had no data for a long

time, so it's really easy.

We have three very clear clades.

However, whenever you get

more and more information,

especially at the

base of the tree,

it becomes not so clear.

That's one of the animals

we're going to look at.

So here's Pisanosaurus,

one of the features of it

is, a very similar

group Kulindadromeus

has been found with feathers,

or at least dermal insulation,

protofeather-like structures.

And it has a very

Ornithischian-like beak,

so there's a lot of

structures within the mandible

that are considered

basal ornithischian.

Heterodontosaurus, one of

the interesting things,

the Heterodontosaur

dentition, that means it has

different dentition,

so it actually has

really sharp canines

and incisors, grinding

surface-like posterior teeth.

Very unusual for archosaurs.

Archosaurs have like

one type of tooth,

it's sharp and that's it.

We're starting to

see diversification

within the group in different

diet and feeding habits.

Eocursor, one of the new 2007,

another new basal dinosaur,

several dozen have been found

within the last dozen years.

Basically every year we get a

new dinosaur coming out here.

So Thyreophora, these

are within that group,

the Stegosaurs, the armored,

the plated dinosaurs,

we have the other armored

dinosaurs, the Ankylosaurs.

Again, these were

much more derived

and this is what Huxley

was working with.

This is what he was

describing initially.

Same with the

Ornithopods, right?

It's a very diverse group

of crested dinosaurs,

the duckbills.

And then, lastly, within

the Ornithischian,

the famous Ceratopsians.

So the Ceratopsians

basically had a very similar

body form, but they

go completely wacky

with their cranial


Triceratops is actually

one of the most boring

of the Ceratopsians with

just a mere three horns.

I mean, they're only like

a meter long, the horn.

But the other ones

had like 13, 20 ...

They get awesome,

but very derived, right.

So, moving over from the

Ornithischians as we know them,

we're going to jump

into the Saurischians.

These, again, the

Theropods here,

which are the

meat-eating dinosaurs,

here we get up into

the Tyrannosaurs.

Then you get into really

cool Edward Scissorhand-like

Therizinosaurs and

then up into the group,

the Maniraptorans that lead

to the evolution of birds.

So here's birds, the

crown group of Therapoda.

Again, classic Tyrannosaurs

and small, little theropods,

Coelophysis there.

Meat-eating, bipedal,

almost all meat-eating,

there's a few herbivores

that throw things wacky.

But, they have an

avian-like breathing system

and they're pneumaticized

all over their body,

very interesting structures.

Similarly, the sauropods

also are hypothesized to have

this avian-style

breathing system,

as well as large

pneumatic structures;

one of the reasons that these

have been united for so long.

So Saurischia, these really

large, long-necked, long-tailed

dinosaurs, Brachiosaurus,


which actually, for

most of my career,

I've been say, "it's

not Brontosaurus, it's

"Apatosaurus, it's a

nomenclatural mess-up."

Yeah, it turns out that

now all the phylogenies

are showing that it

actually is true,

so we can reinvigorate


(audience laughs)

So, who knew?

Now Herrerasaurus.

So we have Pisanosaurus,

that little dude,

as kind of messing around

with the base of the tree,

Herrerasaurus is the other one

and it's been messing with

Saurischia for a long time now.

Herrerasaurus is a basal

dinosaur, for sure,

but it jumps back and forth

between theropod and sauropod.

We can't tell what it is.

You look at one

suite of characters

and it's totally theropod.

You look at another

suite and you're like,

"Yeah, that's totally sauropod."

But it's in the same

animal, so people go,

"Oh, it's a chimera."

Then we find a complete,

articulated skeleton

and we're like, "Oh,

it's not a chimera."

It has characters of both.

So it's somewhere really

close to the tree.

And that's again why we've

always supported the hypothesis

that Saurischia is valid,

that sauropods and theropods

are closely related.

So again, these large dinosaurs,

they came from bipedal

ancestors in the Jurassic,

increase their size,

they get quite big.

We see some really

cool niche partitioning

going on with these critters,

there's all the

dinosaurs, right?

That's the whirlwind

tour of Dinosauria.

So, we know a lot about

these critters now,

especially as we get

into the Cretaceous

closer to the present.

Feathers have been found.

This is one of my

favorite specimens now.

That is a tail of a

dinosaur in amber.

You know, we vertebrate

geeks are going,

"Man, look, it's

a dinosaur tail!"

And the rest of

the world's going,

"Are those ants?

That's awesome!"

There's some really cool

things that are in there

and a dinosaur tail.

But the best part is,

you look at this and go,

"Well yeah, that's a feather."

It really is unambiguous.

And the tail is very

distinctly Dinosaurian.

A) It's really long, has

really well-developed chevrons.

I mean, it looks

like a dinosaur.

Now we just need the rest

of the animal preserved in

amber and that'd be great.

We also have behavioral

traits that are preserved,

or we infer from

the fossil record.

So not only do we

have skeletons,

we have nests, we have

animals that are actually

sitting on the nests.

We have multiple

specimens of this guy,

this is an Oviraptor.

Now, Oviraptor

poorly named because

Oviraptor means egg thief,

but it's not a

thief, it's actually

a really, really good parent.

These are sitting on the

nests likely brooding

and the wings, you can see,

are always splayed

out like this.

They have very

large wing feathers,

but the feathers on

the rest of their body

appear to be pretty

small based on specimens

that have been preserved.

So they're using the

insulation on their wings

to protect their nest,

whether their shading the nest

or incubating, actually

increasing the heat,

whatever they're doing,

they're modulating

the temperature of

the eggs and brooding.

So we get behavioral traits

we can start assigning to

these within the phylogeny.

Egg structures are really cool,

but not super useful because

they all look the same

and they look just like birds'.

But they're novel, they

definitely are the only thing

that has egg structures

that look like this

are avians and dinosaurs.

And then we go into this

little guy, Kulindadromeus,

and notice these

features up here?

Right, those are feathers.

Now, Kulindadromeus is

a little Ornithischian,

so it's on the other line,

not the bird line,

but the Ornithischian.

So we have this,

we have feathers,

here's Kulindadromeus as

artistic interpretation,

the feathers running

down the dorsal spine.

I've been doing some

ecological niche partitioning with Warren Porter in Zoology

and one of the things

that we're finding is that insulating the back gives you

a heck of a lot more

thermal range to work with.

It protects you from the

sun, as well as insulates

in colder climates.

We find it a lot in dinosaurs, it seems to be a real feature,

and we're trying

to figure out why.

But, there it is, an

Ornithischian with feathers.

Oh! Here we go, another one!

We couldn't believe this.

Like, within the

last five years,

we keep finding all these

Ornithischians with feathers.

These are dermal-like

structures up here on the tail

and up along the neck.

So now, if we

start mapping this,

and looking at where these

characters are starting

to show up in the dinosaur tree,

we notice that the

feathered dinosaurs--

Oh, we had a lot of them

from the theropod line--

And we're starting to get

some at the base of the tree,

and we're getting

Ornithischians with feathers

showing up here and there,

at least modified

dermal structures.

But we don't have

any from sauropods.

Okay, that's interesting.

We're mapping on two

different parts of the tree.

Maybe we just aren't finding it.

Of course, that's

certainly a possibility.

But if we look at

other characters

like pneumatic

structures, right?

These are animals that have an

avian-like breathing system,

and one of the things that

we notice is that sauropods

are extremely pneumatized

in their bones.

They have air sacs that are

throughout their entire body.

So whenever it looks like you

have a meter-long cervical

and you have 12 of them,

that's a really long neck.

One of the ways that

they get around having

such a huge mass,

think of the leverage on that

thing at the base of neck,

they pneumatize it,

so the whole neck

is very, very air filled

which reduces mass.

And the pneumatic

structures in the bone

also increase their

respiratory capacity

which assists whenever

you're a 60-ton animal

and relatively warm blooded.

It's seen throughout the

evolution of the sauropods.

When we look at pro-sauropods,

we see just the base

of the cervicals,

up near the thoracic cavity,

some of the thoracic,

or dorsal vertebra

and the sacrum.

Then that transitions into

the more derived sauropods

and the air sacs go

through the entire animal.

Similarly, theropods are

doing the same thing.

There are pneumatic

structures all through

their axial column and even

into some of their ribs.

So that character,

when we plot those,

that really is one of

the strong characters

that unites this, it's unique

to sauropods and theropods.

Things are mapping all

over, what's driving this?

And, of course,

cool things, right?

Planets are really cool.

And dinosaurs.

So we got really envious when

Pluto got all the attention

for being kicked out

of the solar system.

So somebody had

to come up with it

and that's where

Baron et al decided,

"Hey, let's shake up the

dinosaur family tree."

So they ran a series of analyses

and they actually are

pretty robust analyses,

they looked at a very

large swath of Dinosauria.

So they had a very broad

inclusion throughout the tree

and focused, though, on

including these all the new

dinosaurs from the Triassic,

from the beginning,

the dawn of dinosaurs.

So whenever they started

including these dinosaurs,

this is what led to

shaking things up.

But they ran into

a major problem.

Back in the 60s and 70s when

the vertebrate paleontologists

are kind of having this

dinosaur revolution,

one of the things that

came out is that we learned

about this thing

called cladistics.

I don't know, botanists had

been using it a long time

and they were kind of

laughing at us, so we thought,

"Well, hey, we ought

to try this out,"

and started applying

cladistic analyses,

coming up with

phylogenic hypotheses,

testing, these things.

When you did that,

we went from a field

in vertebrate paleontology

where were diagnosing

these morphospecies, right?

We don't have the same

ability to look at species

as you do in the extant,

so we're just using morphologic

characters of the bones,

that's all we had.

This is a description,

what is Crocodylia?

Well, it has all of

these characters.

If you have all of

those characters,

you are probably a Crocodylian.

But whenever you go to the

field, we find a fossil,

we look at the characters,

you don't want to list this

every single time and say

"this defines a crocodile."

So what is a crocodile?

You still use all

this information,

but we're using

phylogenetic taxonomy,

phylogenetic nomenclature.

We're taking all this

data, putting it into

cladistic analysis and

anything within Crocodylia

is then defined as the last

common ancestor of these,

Gavials, Alligators,

and Crocodiles.

So, Crocodylia is

anything that includes

these three animals,

these critters.

So, if you're outside of

that, you're not a crocodile.

It was a very simple

way to describe things.

It simplifies the

description and the diagnosis

of the animal and

how we discuss it.

Any time new characters arise, it doesn't mess with the tree.

It didn't do--

It makes it easier for us,

but it also adds some issues

because, here we go,

here's Dinosauria.

It has been defined

for a long time now

as all descendants of the

most recent common ancestor

of birds and Triceratops.

So it's the inclusion of

anything that includes birds

all the way to Triceratops.

Anything in there is a dinosaur.

Great, and it's monophyletic.

Great, it makes everybody happy.

Saurischia, same thing, it

is anything that includes

pigeons and Saltasaurus

but excludes Triceratops.

So Saurischian is a

clade within Dinosauria

and similarly Ornithischia

is Triceratops

but does not include

pigeons or Saltasaurus.

So that's how we describe and

define these major clades.

However, when this

paper came out,

here's what we had nice,

monophyletic Dinosauria,

Ornithischia, theropods

and sauropodomorpha,

these comprise the Saurischia.

The problem was this new

phylogenetic hypothesis

basically shifted

the base of the tree

and it threw theropods

out of their inclusion

in Saurischia,

or at least their

tie to sauropods,

and said that they were

more closely related to Ornithischians.

The problem is that created

a paraphyletic group,

which, in phylogenic


they didn't really

like that much.

So, enter Herrerasaurus.

We had to redefine everything.

The authors had to

redefine everything

and so they got rid of the

definitions of Ornithischia

and introduced Ornithoscelida

and changed the definitions

of Saurischia and Ornithopod.

So these are the new

definitions of these animals,

but that's one of the

things that their paper did.

So now, all the things that

we had been considering

within the group,

what happened

effectively here is,

without changing the definition,

sauropods were no

longer dinosaurs,

and that would be weird

because they would be excluded

under the definition.

So they had to change

the definition.

This is one of the things

that's causing the stir

in the community.

We're trying to figure out--

Everybody's excited by it

because it's a new hypothesis

and it's completely

different than we've had

for 140 years,

but it's one paper.

A lot of the articles,

"Are we going to go change

"all the textbooks now?

"What's going to happen?"

No, it's a hypothesis,

but it's really intriguing

because it deals

with some characters

at the base of the tree and

trying to figure this out.

So effectively, what we have,

we're looking again,

focusing down here,

it's this part of the tree.

That's all we're looking at.

So, it didn't mess with

any of the relationships

up the tree, it's

just at the base.

But it started when it threw

sauropods out of Dinosauria,

it kind of caused

some eyebrow raising.

So, same thing, this is

from the Baron et al paper.

They're looking especially

in the early Jurassic

through the Triassic

with some inclusion

of later, more derived taxa.

They're getting this

unity of Ornithischians

and Theropoda and a

lot of it is based

on skeletal structures

in the hip and the leg.

But these are all the

characters that are really

diversify or starting at

the base of the clade.

That's the definition, right?

A perforate acetabulum.

So you're down at the base,

there's a lot of stuff going on

and what's what is

being discussed.

Pisanosaurus, that little

guy, is actually now,

as of two weeks ago, is

kicked out of dinosaurs

and they think it's a

basal dinosauromorph.

So keep posted on all of this

because it's not written

in stone quite yet,

but it's really

intriguing to talk about.

So this year, kind of bringing

this home a little bit

to Wisconsin and some of the

stuff that we have been doing

as of late, is looking

at the Triassic rocks

in the Western US.

Now most of the rocks in

the Western US have been

thought to be older than, say

the rocks of South America,

and South Africa where

the earliest dinosaurs

are coming from.

For the most part that's

been completely true.

The recent work that

I've been working on,

Triassic outcrops in Wyoming,

this is getting to be a

really fun place to play

because the rocks in

Wyoming are notorious

for not having fossils.

And, of course, being

a good paleontologist,

I'm going to go look for fossils

in the place everybody

says there aren't any.

It turns out, if you look

long enough, you find stuff.

Either that or you

trick yourself.

We had some nice stunning

scenery at least this year,

we didn't find much this year,

but in the past four

years we've found

some exquisite sites.

So this year we were up in

the Gros Ventre Wilderness

and looking at outcrops that

nobody's looked at before.

But you have to

hike in quite a ways

and it's up in bear country

so it was highly entertaining.

I had to start running

and prepare for that,

because I had to make sure

I could outrun the other

members of my team.

(audience laughs)

We did find some really

nice tracks this year

and I'm going to point this out because this is kind of cool.

When I saw this I'm like,

"Oh man, that is a really

cool theropod track!

"That is beautiful."

But theropods, remember,

they're bipedal.

They don't use their arms.

Their arms have been

reduced pretty significantly

at this point.

But what we have right

up in front, right here,

that's a manus imprint.

Those are two little

toes of the manus.

We have trackways

of these things.

So we have what appears

to be a theropod footprint

but with an Ornithischian body.

Because all the

Ornithischians at the time

are quadrupedal.

So it's kind of interesting.

Now we're starting to

find some new data.

The other aspect of this--

I'm a sedimentologist

by training,

so I really look at rocks

more than anything else,

but we've been

dating these rocks

and trying to get them dated

and they are definitely older

than any of the Triassic rocks

in North America that have

been previously looked at.

So we're finally opening

up a window of time

to look at these and test

some of the hypotheses

that have been generated

by Baron et al.

So we can go look at

finding new dinosaurs.

The goal of all of this

is, "Hey, if we could find

"a new dinosaur in North America

"that's equivalent to

the age of the dinosaurs

"in, say, South America

and South Africa,

"maybe we can start looking at

"the North American contribution

to the rise of dinosaurs

"as well as try to strengthen

or make that base of the tree

"a little bit more

robust and test that."

All of that being said,

we went out to the field,

we found these tracks this year,

but a little over

a year ago now,

we found another specimen.

Now, in the world of

vertebrate paleontology,

this is really exciting,

this is a completely

awesome dinosaur.



(audience laughs)

Right, that's about right.

We looked at this, and when

we collected this material,

at first it was like,

well, we'll collect it,

it's kind of cool


But there are key features,

and this was some of the

features that were pointed out

in the Baron et al paper.

This is the proximal

end of the femur.

So this is the head of the femur

and dinosaurs have a very

distinct femoral head.

We have a little, tiny

dinosaur femur here.

The head of it, this is

the mid shaft showing

where the fifth

trochanter is located,

that's the major part

of the bone that allows

the structure of the tail

to pull the leg back.

It's diagnostic.

Then this little bone right here

that looks like a little

black dot on the screen,

that is the calcano-astragalus.

That's the ankle

joint of this guy.

Again, one of the second

diagnostic characters

of Dinosauria.

We got really lucky.

Even though we have a

smattering of bones,

we have a couple vertebra,

we're lucky enough,

we actually got the femoral

head and the ankle bone.

So we have a new

dinosaur from Wyoming.

The oldest dinosaur, it

looks like, in North America.

We're in the process

of describing this

but this is the kind of

stuff that we're working on

to try to, the

community as a whole,

to really investigate

this hypothesis

because it's intriguing.

So it's forcing us

to go look in areas

that have been unexplored,

just haven't been looked at.

It's been a fun challenge.

That's it, that's the shake

up in the dinosaur family tree

is this idea of

looking at the base,

the more information we have,

the less clear it has become.

As new information comes in,

hopefully we will be able

to strengthen hypotheses,

reject or support this,

figure out exactly what

the origins of dinosaurs

really looked like.

And as of now, we

still don't know

but that doesn't mean we

threw out a lot of stuff.

They're still our lovely

dinosaurs as we know and love.

That's kind of what's

going on in this field.

With that I say, are

there any questions?

Because I'm going to

open it up to you.

Question in the back?

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