4 août 2015

Ptérosaures


Non, contrairement à la croyance populaire, les ptérodactyles ne sont pas des dinosaures. Ils ne sont donc pas affiliés aux oiseaux. Ces reptiles ont développé leur capacité de voler indépendamment, comme les chauve-souris.

Alors, que sont-ils? Et surtout, comment ont-il évolué leurs ailes?

Extrait de l'article:

(...) The name “pterodactyl” is an unfortunate artifact. It was the name given by naturalist and “father of paleontology” Georges Cuvier, to a fossil unearthed in 1801. The flying reptile got its name for its long “finger,” which stretched out to form a wing. It was soon joined by more fossils of winged fingers. Some had teeth and some didn’t. Some were the size of giraffes and some could rest on a person’s hand. They were shaped differently, and clearly ate different diets. The dactyl name just didn’t describe any group of animals any more, and so in 1834 these creatures got the more general name of “pterosaurs.”

(...) The ankle joint of a member of Avemetatarsalia is slightly different from other members of Archosauria. A section of bone that would have been part of an early crocodile’s leg is part of an early member of the group Avemetatarsalia’s foot. This makes the foot work in a slightly different way—a way that can be exploited to get up one one’s back legs and use one’s front arms to grasp, to walk, or to fly. There are other distinguishing characteristics, including elongated metatarsals, a longer neck, and differently-constructed legs, but it’s the ankle that’s the give-away.

What did the members of the Avemetatarsalia do with their snazzy new ankles? Some became Scleromochlus taylori. (...) however, it has a relatively primitive ankle structure.



That ankle structure was shared by every animal in the group Pterosauria. 

(...) But they were on a separate branch of the classification tree from the the members of Dinosaurmorpha—which still weren’t dinosaurs. And they weren’t among the group of animals that branched out from Dinosaurmorpha to become Dinosauriformes—still not dinosaurs. It took yet another branch to get to Dinosauria. 



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