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  • [♪ INTRO]

  • When you picture a fossil, the first thing that comes to mind is probably a dinosaur bone.

  • We've all seen those terrifyingly enormous skeletons that go all the way up to the museum's ceiling.

  • But what about their brains?

  • And their blood vessels, and skin, and other organs?

  • Most of the super old fossils we've found are just bones

  • because it's a lot easier to preserve bone than soft tissue for millions of years.

  • But we have found some fossilized soft tissue from dinosaurs, as well as other animals that lived millions of years ago,

  • including a fossilized piece of dinosaur brain. It's just really rare.

  • Before any part of an animal could start being fossilized, it first needed to, you know, die.

  • And then, for most types of fossils, it needed to be buried.

  • For the most part, that didn't happen right away.

  • Instead, the bodies would just sit out there in the open.

  • Perfect targets for scavengers and microbes to come pick off and decay the soft tissue,

  • so that by the time the animal was buried, only the bones were left.

  • Over time, minerals would seep into where the bones were buried

  • and harden them into the fossils we find today.

  • Paleontologists can sometimes use these fossilized bones to indirectly study soft tissues using what are known as trace fossils:

  • things like skin patterns left in the mud.

  • But very, very rarely, they'll find an animal fossil that includes actual fossilized soft tissue,

  • because the animal was buried quickly enough for its soft tissue to fossilize before it decayed.

  • Some of the most important examples of this are fossils from the Cambrian Explosion,

  • a period of time about 550 million years ago

  • that saw one of the most drastic increases in the number of species on Earth.

  • But a lot of those species were soft-bodied, meaning that they had no bones.

  • So normally, we wouldn't expect to find fossils of them.

  • Unfortunately for them, but lucky for us, some of these animals were buried almost instantly in events like underwater mudslides,

  • so fossilization could start right away.

  • Without the soft tissue fossils we've found from the Cambrian Explosion,

  • there's a lot we'd never know about one of the most exciting times in the history of life.

  • We've also occasionally found soft tissue from a few other animals, including dinosaurs.

  • In 2005, for example, researchers at North Carolina State University claimed to have found actual blood vessels and other soft tissues

  • preserved in a T. rex fossil, meaning that they weren't fossilized.

  • They'd just been kept from decaying.

  • The team suggested that the tissues were preserved because the iron in the dinosaur's blood turned into formaldehyde,

  • but the findings are still disputed because direct preservation of organic matter over millions of years really shouldn't be possible.

  • With or without formaldehyde.

  • There have been other, less controversial findings, though.

  • In late 2016, paleontologists found a 99-million-year-old dinosaur tail perfectly preserved in amber.

  • And we've found a few dinosaur fossils that contain fossilized skin and feathers,

  • like an Ornithomimus fossil discovered in 2009.

  • We already knew that Ornithomimus was weirdly similar to the modern ostrich,

  • but the new fossil showed us that it also had the same arrangement of feathers on its body and bare skin on its legs,

  • probably to help regulate its body temperature.

  • And, yes, we've found fossilized dinosaur brain.

  • In 2016, researchers announced that they'd found a pebble-sized fossil that contained brain tissue.

  • They don't know exactly which dinosaur it came from, but it's about 133 million years old.

  • That's the only dinosaur brain tissue we've ever found,

  • but there are plenty more fossils waiting to be discovered.

  • So who knows what we'll learn about the softer parts of dinosaurs someday.

  • Thanks for watching this episode of SciShow!

  • If you're interested in learning more about dinosaurs and the history of life on Earth in general,

  • you can check out our new sister show, Eons, over at youtube.com/eons.

  • [♪ OUTRO]

[♪ INTRO]

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恐龙的大脑在哪里?(Where Are All the Dinosaur Brains?)

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    joey joey 發佈於 2021 年 05 月 13 日
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