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  • 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 deliciousdinosaur!

  • 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, andfun 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

  • We have all heard that birds are dinosaurs, but what exactly does that really mean?

  • That's a great question , Anna.

  • So the way that we can even tell that anything is related to something else is through 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?

  • Birds don't have hands!

  • Birds actually DO have hands, they just don't really look like hands anymore.

  • So if you've eaten a chicken wing, or at least you know 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.

  • So these are like the original chicken fingers!

  • 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!

  • That's first digit. This is second digit. And third digit.

  • 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?

  • 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.

  • 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, orfurcula”, 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.

  • Ok let's get this wishbone out in one piece.

  • This is nerve wracking.

  • I got it!

  • You did it!

  • Bravo!

  • So all birds will have a form of this,

  • and all dinosaurs in this part of the tree also had something like this?

  • We've found a furcula in most Theropod dinosaurs' fossils that we've found around the world.

  • 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.

  • So actually one of the similarities between birds and theropods, and how we know that

  • birds are theropod dinosaurs, is inside their bones.

  • This is another one of those tibiotarsus bones

  • Drumstick bones!

  • 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.

  • 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?

  • 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.

  • 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?

  • Exactly!

  • 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.

  • So our chicken we've got one, two, three fingers.

  • 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.

  • Ok, so to get to the next identifying characteristic of this bird,

  • we're really gonna have to dig in there.

  • I'm just ripping parts off here.

  • It's soit's kinda fun actually.

  • It's like The Brain Scoop crossed with a cooking show right now.

  • I mean honestly, this entire scene is so macabre.

  • It's so bad.

  • It's awesome.

  • The darkest thanksgiving!

  • 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.

  • So we know that birds are Tetanurans, but is that the last branch

  • or can we get even more specific?

  • We can get even more specific.

  • There's a few more branches to go, before we get to what we callcrown birdsor 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.

  • So we've got our backward facing pelvis for the maniraptorans.

  • Is there another branch beyond this?

  • Yeah, so there's Avialae

  • So Aves is part of Avialae.

  • Aves is modern birds and 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

  • 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.

  • Ok, my holiday dinner is never gonna be the same.

  • It's gonna be way awesomer, and a little grosser.

  • But that's ok.

  • 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.

  • 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?

  • 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.

  • Ok, like every holiday dinner, this one has to end with the traditional breaking of the wishbone.

  • Grab a side guys.

  • 3-2-1…

  • What did you wish for?

  • I wished for everyone to stay curious!

Hey smart people, Joe here.

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B1 US dinosaur chicken bird family tree finger tree

The Dinosaur On Your Thanksgiving Table

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    Evangeline posted on 2018/11/20
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