Wikijunior Dinosauri/Plesiosauria: differenze tra le versioni

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Nuova pagina: {{WIP}} right|thumb|230px Il Plesiosaurus non è un dinosauro, bensì un grande rettile acquatico. ''Plesiosaur'' in greco significa "più vicino ai rettili...
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Versione delle 17:53, 1 gen 2008

Il Plesiosaurus non è un dinosauro, bensì un grande rettile acquatico. Plesiosaur in greco significa "più vicino ai rettili". Gli è stato assegnato questo nome perché questa creatura è a metà fra un rettile ed un pesce.

Come erano?

An early image of the Plesiosaurus, surprsingly accurate with only one problem.

There were different types of Plesiosaurs which were different from each other in size and in shape. The shortest were 2.5 metres long and the longest were 14 metres long! That is about as long as 8 adults lying in one long line! They all had long necks with small heads on the end. Their tummies were oval-shaped with two front flippers and two back flippers. They had long tails, though much shorter than their necks.

Scientists first thought that they swam close to the surface of the water (as the picture on the left shows). This way they could stick their head above the water and look down on fish. But because their eyes are placed facing slightly upwards, this is probably not true. They probably swam completely underwater and used their long necks to dart their heads towards fish. Plesiosaurs were very succesful, and there were many types.

Cosa mangiavano?

They ate fish, squids, mollusks and other small sea creatures. Recently, scientists have found evidence that the Plesiosaurs may have also been "bottom-feeders". That is they would feed from the bottom of the sea - on things like clams and snails.

Quando vissero?

They lived from the early Jurassic to the end of the Cretaceous period. That is from about 220 million years to about 65 million years ago. Plesiosaurs, like dinosaurs, lived in the Mesozoic era.

Dpve vivevano?

Some people think that they could climb out of the water and crawl around on land, like seals. But other scientists disagree with this. Either way they would have spent a lot of their time under water. And because they were air-breathing animals, they would have to come up to the water surface for air every now and then.

Their fossils were found in England, Germany, Japan, Australia and USA. They lived also in Manitoba, Canada

Come furono scoperti?

The first Plesiosaur was discovered in 1821 by Mary Anning, in England.

Cosa non sappiamo ancora di loro?

File:Nessie ill artlibre jn.jpg
Il misterioso mostro di Loch Ness

The most famous mysteries around these creatures is the Loch Ness Monster. There are alot of stories of some large creatre in the lake called Loch Ness in Scotland. Most descriptions of the monster are close to what the Plesiosaurs must have looked like. Many people belive in it.

In 1977, some Japanese fishermen off the coast of New Zealand found a very rotten carcass of some large creature with flippers. It was so rotten that it was very hard to tell anything from it, but a lot of people believed that it was a Plesiosaur. Some scientists however think it was just a certain type of shark, just fallen to bits because it was so rotten.

What do we need to learn?

  • How flexible were their necks? Scientists don't agree on this.
  • Is there any truth to the stories around them?