3 janvier 2016

Pattes de serpent

L'évolution est fascinante et celle des serpents l'est particulièrement.

Ainsi, vous avez sous les yeux une photo du plus ancien fossile de serpent trouvé à ce jour.

Et il a quatre pattes.

Extrait de l'article:

The roughly 120-million-year-old snake, dubbed Tetrapodophis amplectus (literally, four-legged snake), likely didn't use its feet for walking. Instead, the appendages may have helped Tetrapodophis hold onto a partner while mating, or even grip unruly prey, said study co-researcher David Martill, a professor of paleobiology at the University of Portsmouth in the United Kingdom.

Previous research has detailed two-legged snake fossils, but this is the first known snake ancestor to sport four legs, he said. It likely evolved from terrestrial-burrowing creatures, and was a transitional animal that lived during the shift from ancient lizards to modern-day snakes, he added. 

"We've found the ancestor of all snakes," Martill told Live Science. "We have found the missing link between four-legged lizards and snakes."

(...) The researchers found several indications that the fossil is, in fact, a transitional snake. Unlike lizards and crocodiles, Tetrapodophis has faint impressions of a single row of belly scales, a signature still seen on snakes today.

When the researchers used ultraviolet photography to examine Tetrapodophis' gut, they found partly digested bone fragments that the camera highlighted in different colors. These remnants suggest the snake ancestor ate vertebrates, just as modern carnivorous snakes do.

It's likely that Tetrapodophis used its long body to constrict prey, such as lizards and frogs, Martill added.

Moreover, the fossil had other classic snake features, including a short snout, long braincase, elongated body, fanged teeth and a flexible jaw that could swallow large prey, the researchers said. It also has a similar vertebrae column that allows the snake to be extremely flexible, they said.

However, Tetrapodophis doesn't have a long, laterally compressed tail that is usually seen in marine animals, which suggests that it descended from burrowing terrestrial, and not marine, creatures, the researchers said. 

Tetrapodophis and other ancient snakes hail from Gondwana, the ancient supercontinent that covered the Southern Hemisphere. (A January study reported snake specimens that were from the Northern Hemisphere, but Martill says it's unclear whether these are snakes or lizards.)

Allez voir l'article pour une photo en gros plan des pattes arrière de l'animal, parfaitement préservées.

À lire également:

Serpents à pattes

Pourquoi les serpents ont-ils perdu leurs pattes?

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