WEBVTT - How Did Plesiosaurs Use Their Flippers to Swim?

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<v Speaker 1>Welcome to brain stuff from how stuff Works. Hey, brain stuff,

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<v Speaker 1>It's Christian saga. From two hundred and twenty to sixty

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<v Speaker 1>six million years ago, a strange order of marine reptiles

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<v Speaker 1>called plesiosaurs roamed Earth's oceans. Though they were a diverse

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<v Speaker 1>bunch in many respects, every known species did share one

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<v Speaker 1>major trait. They all had four broad, paddle like flippers,

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<v Speaker 1>and in most cases the hind pair almost looked like

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<v Speaker 1>a duplicate of the front set, both in size and shape.

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<v Speaker 1>That makes plesiosaurs, which were not dinosaurs but lived at

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<v Speaker 1>the same time, unique among ocean going vertebrates. That's because

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<v Speaker 1>no other marine reptile or mammal extinct or extent sports

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<v Speaker 1>four flippers of similar size. So how did this unique

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<v Speaker 1>body plan work. Researchers might have just found the answer.

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<v Speaker 1>On aug an international team of scientists published a new

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<v Speaker 1>study on plesiosaur locomotion. Headed by paleontologists Luke Musket. The

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<v Speaker 1>group used measurements from a pair of British species to

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<v Speaker 1>construct two replica flippers, one four limb and one hind

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<v Speaker 1>limb with three D printing technology. These were affixed to

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<v Speaker 1>a custom built robot which moved the replicas around in

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<v Speaker 1>a tank of water to see exactly how the paddles

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<v Speaker 1>would turn things up. Musket and company released colorful dyes

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<v Speaker 1>into the tank as well, and tracked their motion through water. Afterwards,

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<v Speaker 1>the scientists put the robotic legs through numerous simulations designed

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<v Speaker 1>to test out different swimming styles. They found that the

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<v Speaker 1>most energy efficient stroke called for both flippers to work

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<v Speaker 1>in concert. When the front limb flapped in this test,

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<v Speaker 1>it created two vortices in the water. As the current

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<v Speaker 1>pushed these backward, the hind flipper weaved in between them.

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<v Speaker 1>By capitalizing on the wake generated by its frontal counterpart,

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<v Speaker 1>the rear limb made its own flapping motion six more powerful,

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<v Speaker 1>and this finding actually contradicts a study which argued that

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<v Speaker 1>plesiosaurs swam like sea turtles, using their four limbs to

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<v Speaker 1>push themselves forward while their rear paddles acted as rudders.

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<v Speaker 1>Using the robot, muskets team also tested this existing hypothesis.

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<v Speaker 1>They found that the rear paddles tended to produce drag

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<v Speaker 1>if kept in a stationary position, but by using all

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<v Speaker 1>four paddles to actively generate thrust, a plesiosaur could move

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<v Speaker 1>more efficiently. However, the co authors acknowledge that, like most

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<v Speaker 1>aquatic animals, plesi asaurs probably adjusted their swimming style as

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<v Speaker 1>the situation called for it. Furthermore, the study is complicated

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<v Speaker 1>by the fact that several plesiosaur species had four limbs

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<v Speaker 1>that were noticeably longer than their rear ones or vice versa.

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<v Speaker 1>Looks like follow up research will have to take species

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<v Speaker 1>specific data into account. Today's episode was written by Mark Mancini,

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<v Speaker 1>produced by Dylan Fagan, and for more on this and

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<v Speaker 1>other topics, please visit us at how stuff works dot com.