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  • (water splashes) (ominous music)

  • - [Narrator] Sea monsters are considered

  • to be mythical creatures at the center of tall tales.

  • (lighting crackling)

  • But science tells a story of real-life monsters

  • lurking in Earth's prehistoric seas,

  • monsters called plesiosaurs.

  • Plesiosaurs were ancient marine reptiles

  • that first appeared about 215 million years ago.

  • They belonged in the order Plesiosauria,

  • which is divided into two groups:

  • the long-necked plesiosaurs and the short-necked pliosaurs.

  • Plesiosaurs were massive animals.

  • They grew up to 43 feet long,

  • with large bodies and small, triangular heads

  • with smooth sharp teeth.

  • Their most signature feature was their long necks.

  • Spanning half the length of their body,

  • plesiosaur necks had up to 76 distinct vertebrae,

  • over 10 times more than that found in humans.

  • Older depictions portray these necks

  • as willowy and snake-like,

  • but recent discoveries have shown

  • that they were, in fact, relatively stiff.

  • This allowed the plesiosaurs to stay streamlined

  • while swimming or while hunting fish, squid, and clams.

  • While the Plesiosaurs evolved long necks and small heads,

  • their pliosaur cousins went the opposite direction.

  • Their necks were short and their heads were large,

  • measuring up to 10 feet long.

  • But much like plesiosaurs, pliosaurs were massive,

  • growing up to 50 feet long

  • and weighing almost 100,000 pounds.

  • Despite their large size, pliosaurs were excellent swimmers,

  • capable of reaching speeds near 10 kilometers per hour.

  • Their speed, along with their great size,

  • allowed pliosaurs to become ferocious predators,

  • devouring large marine animals and even other Plesiosauria.

  • Despite their differences,

  • pliosaurs and plesiosaurs shared a few key features

  • that were characteristic of the genus Plesiosauria.

  • They used all four of their flippers to swim

  • in a form of underwater flight,

  • similar to the movement of a dragonfly.

  • And while they spent their entire lives in the sea,

  • plesiosaurs had no gills.

  • Rather, they were air-breathers,

  • coming up to the surface for oxygen before every dive.

  • By about 66 million years ago,

  • these powerful predators died out;

  • but today, they continue to be a point of fascination,

  • inspiring legends as grand as the monsters themselves.

(water splashes) (ominous music)


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Plesiosaurs 101 | National Geographic

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    Elise Chuang に公開 2021 年 11 月 03 日