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  • Thanks to Skillshare for supporting this episode of SciShow.

  • [ intro ]

  • Though it was a contentious idea for a long time, we know today that birds are the last

  • living dinosaurs.

  • But there seems to still be a lot of confusion about what that means.

  • You might think that birds are the descendents of dinosaurs, and that is true

  • but they didn't just appear after the other dinos died out.

  • They also lived alongside them.

  • Think ancient egrets riding on Triceratops.

  • Ok, we don't know that that was a thing, but it's not out of the question.

  • Because if you went back in time,

  • you would see some pretty familiar-looking feathered animals filling many of the same

  • ecological roles that modern birds do today.

  • Archaeopteryxthat half-bird half-lizard thing

  • gave us our first clue that birds evolved from dinosaurs all the way back in the 1860s.

  • But for more than a century, our actual knowledge of what birds looked like in the Mesozoic

  • Era was pretty sparse.

  • In the past forty years, though, scientists have unearthed all sorts of new fossils,

  • confirming that birds aren't just an afterthought of the dinosaur lineage.

  • And if you know anything about the paleontology community,

  • you will not be surprised to hear this has lead to some pretty heated debates

  • but more on that later.

  • Let's start with a very old bird: Archaeornithura.

  • Found in China, this bird lived over 130 million years ago,

  • making it the oldest known ornithuromorph—a grouping that includes modern birds.

  • Despite being only about 20 million years younger than Archaeopteryx,

  • nobody would confuse this animal with a lizard.

  • While Archaeopteryx had a long reptilian tail, Archaeornithura had a short little rump with

  • fan-shaped tail feathers, like a modern bird.

  • And while it still had a two tiny claws, it also had a special set of feathers on its

  • wings known as alula,

  • which are really important for controlling flight.

  • Archeopteryx could maybe fly, albeit awkwardly.

  • But with its new-and-improved tail and the alula,

  • Archaeornithura probably had some real maneuverability and may have flown alongside pterosaurs.

  • But when it came to mealtime, it was probably a wading bird.

  • Most likely, it darted around shorelines looking for small invertebrates to snack on, kind

  • of like sandpipers do today.

  • Actually, a lot of the early Mesozoic birds that paleontologists have found probably lived

  • and ate near water

  • though, not all.

  • Take, for example, a little bird called Eogranivora.

  • It lived in the same area of China as Archaeornithura, though probably a few million years later.

  • It was also a good flier, though it likely ran along the ground a lot

  • maybe to escape from tiny Tyrannosaurus relatives.

  • What makes Eogranivora interesting, though, isn't it's feathers or legs, but rather,

  • its diet.

  • When scientists examined the fossil,

  • they found what looked like seeds in its digestive tractthe remains of the bird's last meal.

  • There was evidence it had a special organ called a gizzard

  • where it stored swallowed pebbles to help it grind these up.

  • And that, combined with a toothless beak, has led scientists to declare Eogranivora

  • the oldest known seed-eating bird.

  • Fossils like these have taught paleontologists that many signaturebirdtraits are

  • truly ancient and have occurred in lots of divergent lineages.

  • Because though Eogranivora and it's kin looked a lot like modern birds, and they belong

  • to the same larger group of birds,

  • technically, they weren't modern birds.

  • They were more like old cousins.

  • Modern birds all fall under the Neornithes—a subgroup of ornithuromorphs.

  • And debates about when those evolved

  • and whether they lived alongside dinosaursget really heated.

  • You see, you get two very different answers depending on how you go about trying to determine

  • when modern birds arose.

  • Molecular clocks suggest the first modern birds appeared fairly far back

  • up to 100 million years ago in the Cretaceous Period, the last period of the Mesozoic Era.

  • But the fossil record for them in the Mesozoic remained nonexistent for decades,

  • which suggested they only really evolved after the dinosaurs died off.

  • This is often known as therocks versus clocksproblem.

  • They named it, it's that big of a deal.

  • Then, in 2005, scientists announced they'd found something amazing: a Mesozoic duck.

  • Or duck-relative, at least.

  • Named Vegavis iaai, it was actually unearthed in Antarctica in 1992.

  • And at first, paleontologists weren't sure what it was, but now,

  • they place it in Anseriformes, the order of birds that contains ducks, geese, and swans.

  • It even has the oldest known syrinx, a voice-box-like organ in birds,

  • which would have let it make honking or quacking noises.

  • What's really special, though, is that it was found in a layer of rock that's definitely,

  • 100% pre-mass extinction.

  • This means when Vegavis was alive, duck-billed dinosaurs and raptor-like dromeaosaurs

  • would have walked Antarctica's beaches.

  • And this little duck may have had to dive past sea monsters like plesiosaurs and mosasaurs

  • to get its food.

  • The fossil was the first solid evidence that modern birds were already beginning to diversify

  • into the many different families we know today before other dinos died out.

  • And now, many paleontologists think that there were early ostrich relatives running alongside

  • tyrannosaurs,

  • ancestral chickens hiding from velociraptors, and maybe even penguins snacking on fish!

  • Of course, the rocks vs. clocks problem hasn't been completely solved.

  • As you may see if there's any paleontologists in the comments.

  • There are still a lot of questionsand arguments

  • about things like how many families of birds there were in the Cretaceous and how the mass

  • extinction affected them.

  • But the more we learn, the more it's becoming clear that birds aren't just the descendants

  • of dinosaurs.

  • Millions of years before the other dinosaurs went extinct, birds had already become diverse,

  • complex, and recognizable,

  • and they were filling some of the ecological niches their kin do today.

  • So, yes, if you went back in time, you would see some distinctly avian-looking creatures

  • amongst T. rex, Triceratops, and the other famous dinosaurs.

  • And maybe even riding on them.

  • Who knows?

  • Outro: For us to know what these extinct creatures

  • actually looked like,

  • we rely on the imaginations of illustrators.

  • If you're interested in learning how to give life to ancient animals through art,

  • Skillshare offers a bunch of courses on illustration -- and more.

  • Illustrator Yuko Shimizu offers a course calledInk Drawing Techniqueswhere she shares

  • all the basics of ink and brush.

  • She'll help you learn to create bold, high-contrast illustrations as well as covering fundamentals

  • like brush and paper types.

  • And there are over 25,000 other courses on Skillshare to cover every interest, from design

  • to productivity.

  • Over 7 million creators are learning with Skillshare.

  • The first 500 SciShow viewers to sign up using the link in the description can join them

  • with a 2 month free trial.

  • Yeah, free -- so you can give it a spin and see if it's right for you.

  • [ outro ]

Thanks to Skillshare for supporting this episode of SciShow.

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The Birds That Lived in The Age of Dinosaurs

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    joey joey に公開 2021 年 05 月 13 日
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