Hey smart people, Joe here.
This holiday season, I bet many of you are going to be sitting down with family and friends
to celebrate.
And I bet a lot of you are going to be eating some nice delicious… dinosaur!
Birds are dinosaurs!
But why is that?
That’s what we’re going to talk about today.
[OPEN]
Today I’m here with my friends Anna Rothschild who makes Science Magic Show Hooray! at The
Washington Post, and… fun fact, she’s 25% mashed potatoes.
It’s true!
I am.
And Dr. Shae Montanari, who is not only a pumpkin beer aficionado, but is a dinosaur
expert extraordinaire.
Really happy to be here, Joe
So we have all heard that birds are dinosaurs, but what exactly does that really mean?
The way that we can tell that anything is related to something else is by looking at
their anatomy and what kind of characteristics that they share.
These are called synapomorphies, traits shared by two or more groups of organisms, and derived
from a common ancestor.
Like how humans and chimps both have opposable thumbs.
So, there’s different kinds of dinosaurs and we can look at the characteristics of
birds to find out exactly what kind of dinosaurs they are.
There’s actually lots of clues preserved in their bones that show that they are very
closely related, and that birds are actually dinosaurs.
And we’re gonna find those today, with this!
So, we couldn’t get a turkey, it’s not quite Thanksgiving yet.
But everything we show you we promise you can do at your holiday table with the people
you’re celebrating with, and explain to them the science of why you’re eating a
dinosaur.
VO: In the 1860s, scientists unearthed the most famous feathered dinosaur fossil: Archaeopteryx.
Early defenders of evolution like Thomas Henry Huxley began to suggest that these extinct reptiles were
so similar to birds, they must be related.
But the idea didn’t really catch on until the 1970s, when new fossils filled in more
empty branches on the dinosaur family tree…
VO: About 250 million years ago, a group called Archosaurs split into Crocodilian reptiles,
and Dinosaurs.
And a lot of evolution has happened since that split.
Ok, so there’s two groups of dinosaurs, and that’s the Ornithischian and the Saurischian
dinosaurs.
And that split happened about 240 million years ago.
And the way we know that birds belong to the Saurischian group is mainly because of their
hands.
Wait, hands?
A: Birds don’t have hands!
S: Birds actually DO have hands, they just don’t really look like hands anymore.
If you’ve ever eaten a chicken wing, or held on to a chicken wing, you’ve been shaking
hands with a chicken!
Can we dig into this chicken and check it out?
I think it’s time to check it out.
Let’s go find a chicken hand.
A: So these are like the original chicken fingers!
-- J: I usually dissect these with my teeth,
you’re doing it completely differently So that little skinny part of the wing, at
the end, that you don’t typically eat…
This little nubbin?
That little nubbin, is the finger of the chicken, that’s gotten super reduced.
I accidentally broke off the very tip of the bird finger, but here is like, the second
digit.
The very, very tip of the finger.
It’s a tiny bird finger.
Joe, I’m going to let you hold that as well!
The length of the three bird fingers inside a wing narrows down which group of dinosaurs
birds descended from
The second finger is longest in birds and in Saurischian dinosaurs.
That’s a big way we know that birds belong to the Saurischian group as opposed to the
Ornithischian group.
So birds are Saurischian dinosaurs, but are all Saurischian dinosaurs birds?
S: No, they are not.
That’s a great question.
So even within Saurischian dinosaurs, as we’re walking up this dinosaur family tree, there’s
another group that branches off and we can tell which one birds are a part of, and it’s
the Theropod dinosaurs.
S: And the one bone that is the biggest clue of Theropod dinosaurs is something that you’ve
probably played a little game with after your thanksgiving dinner: The wishbone!
Right here.
Cooool!
-- I think it’s time to dissect a wishbone.
What does the wishbone do?
Does it serve a purpose for flight or for something else?
It helps birds get their wishes!
Oh right, of course!
Besides helping all their dreams come true, the furcula is actually support for the flight
muscles.
A wishbone, or “furcula”, is actually a bird’s collarbones, but instead of two
separate collarbones like we have, theirs is fused into one.
Wishbones have only been found in birds and Theropod dinosaurs, like Allosaurus, and they
draw a clear line from those extinct creatures to our modern feathered friends.
J: Ok let’s get this wishbone out in one piece.
This is nerve wracking.
I got it!
S: You did it!
A: Bravo!
-- J: So all birds will have a form of this,
and all dinosaurs in this part of the tree also had something like this?
S: We’ve found a furcula in most Theropod dinosaurs’ fossils that we’ve found around
the world.
-- J: We’ll save this for later.
VO: Fossil wishbones are one of the most important pieces of evidence we have that birds descended
from Theropod dinosaurs.
S: So actually one of the similarities between birds and theropods, and how we know that
birds are theropod dinosaurs, is inside their bones.
S: This is another one of those tibiotarsus bones…
J: Drumstick bones!
S: Drumstick bones, and I have channeled all of my rage and broken this one in half, and
look inside, and you can see that the walls of the bone is very thin and basically hollow.
So when people say that birds have hollow bones, that’s what they mean.
There’s very little spongy bone on the inside, and there’s a very thin wall, which makes
it easier for them to fly.
J: Theropod dinosaurs had these hollow bones too.
So did that help them be more agile, you know, go in for more Jurassic Park type kills?
S: Right, that’s a great question.
Because theropods had a lot of the characteristics that modern birds do, but they didn’t fly.
So these characteristics must have been helpful for them to do other things.
And hunting is definitely one of them.
J: That’s the cool thing about evolution, is that something that could have helped theropods
that didn’t fly in one way, birds could have taken advantage of that in a completely
different way as light weight for flight, right?
S: Exactly!
S: So even within Theropods, as we’re going down the family tree, there’s more branches,
and the way we can tell which one birds fall in is how many fingers they have.
VO: Around 200 million years ago, Theropods split.
One branch kept four or even five fingers, but a branch called Tetanurae all descended
from an ancestor with just three fingers.
Our bird?
Three fingers!
Later, some Tetanurans, like T. rex, even lost an additional finger, going from three
to two!
Poor T. rex.
J: So our chicken, we’ve got one, two, three fingers.
-- S: Ok, so to get to the next identifying characteristic
of this bird, we’re really gonna have to dig in there.
J: I’m just ripping parts off here.
It’s so… it’s kinda fun actually.
It’s like The Brain Scoop crossed with a cooking show right now.
A: For sure.
S: Oh man.
A: I mean honestly, this entire scene is so macabre.
S: It’s so bad.
J: It’s awesome.
The darkest thanksgiving!
J: You can do any of this with a turkey, it’s just going to be a lot messier.
Which in my book, makes it more fun.
-- A: So we know that birds are Tetanurans, but
can we get even more specific?
S: We can get even more specific.
There’s a few more branches to go, before we get to what we call “crown birds” or
living birds.
And birds are a specific kind of theropod called Maniraptoran theropods.
So Maniraptora, one of the characteristics of this group is that the hips point backwards.
Specifically, the rearward-tilted bone is a part of the pelvis called the pubis.
J: So we’ve got our backward facing pelvis for the maniraptorans.
Is there another branch beyond this?
S: Yeah, there’s still more branches to go,
-but the one we’re going to end on is Avialae.
So Aves is part of Avialae.
Aves is modern birds So a big difference between the kinds of theropod
dinosaurs that you’re probably envisioning In your head, like Velociraptor, and birds,
is a tail.
So birds actually do not have tails.
This little bit at the end represents what’s left of the dinosaur tail, called a pygostyle.
So the pygostyle is the last remnants of a long fluffy feathered theropod tail, and narrows
down the bird/dinosaur family tree even further.
So.
Birds are Avian
Maniraptoran Tetanuran
So.
Birds are Avian
Maniraptoran Tetanuran
Theropod Dinosaurs.
And these anatomical features are just a few of the similarities that scientists have used
to place birds in the dinosaur family tree.
There’s even more, from the shape of their necks, to their weird feet, to yes, even feathers.
J: Ok, my holiday dinner is never gonna be the same.
It’s gonna be way awesomer, and a little grosser.
But that’s ok.
S: So if you want to do this at home, you definitely can, and if you want to learn more,
there’s links in the description.
J: You know we’ve taken a deep dive inside of a dinosaur to see what makes them what
they are, but what were they like on the outside?
What did they act like?
A: That is an excellent question!
And if you want to learn more about what colors dinosaurs were, or even what sounds they made,
head on over to my channel where Joe and I explore those questions.
J: Ok, like every holiday dinner, this one has to end with the traditional breaking of
the wishbone.
Grab a side guys.
3-2-1…
A: What did you wish for?
S: I wished for everyone to stay curious!