2 mars 2015

Quand les fossiles nous parlent...

La plupart du temps, les informations que nous livre un fossile sont limitées. Un cadavre squelettique nous dit bien peu de choses à propos des comportements de l'animal lorsqu'il était en vie. Mais de temps en temps, les paléontologues tombent sur un trésor: un fossile d'animal qui est mort subitement, alors qu'il était en pleine action! Il est alors possible d'apercevoir le comportement d'un animal disparu depuis des millions d'années! NS nous offre un aperçu de quelques-uns de ces fossiles.


Discovered: Gobi desert, Mongolia, 1971
Age: 74 million years
Location: Mongolian Dinosaur Museum, Ulan Bator

They will remain forever locked in mortal combat. The Velociraptor has sunk its deadly foot claw deep into the neck of the herbivore, a boar-sized creature called Protoceratops. This vicious attack may have hit the carotid artery – a lethal blow.

But the Protoceratops fought back. It has thrown the Velociraptor to the ground before it, and its jaws are locked on to the predator's right arm. The bite appears to have broken the Velociraptor's arm. 



Discovered: Gobi Desert, Mongolia, 1994
Age: 83 to 66 million years
Location: Mongolian Dinosaur Museum

The first oviraptor was discovered in Mongolia in 1922. It was given its name, which means "egg thief", because it was found near a nest of what appeared to be Protoceratops eggs.


In 1993, however, Mark Norell of the American Museum of Natural History found a fossilised embryo in an identical egg. He recognised it as a kind of oviraptor, suggesting the original thief was in fact a parent.


Discovered: Glen Rose, Texas, 1938
Age: 111 million years
Location: Part at the American Museum of Natural History

The massive sauropod fled along the shore closely pursued by a huge predator similar to T. rex. The trail of footprints they left behind survived for over 100 million years.


Discovered: Gujarat, India, 1986
Age: 68 million years
Location: Geological Survey of India

Unlike some dinosaurs, the giant, long-necked sauropods did not care for their eggs. Adults have never been found near nests, so it seems that sauropod hatchlings had to fend for themselves from the start. And that left the way clear for predators to feast on them as they emerged.

One of these predators was a 3.5-metre-long snake called Sanajeh indicus. Towards the end of the age of the dinosaurs, one decided to raid a nest of a sauropod eggs, perhaps attracted by the noise of hatchlings breaking out of their shells.


Discovered: Messel Fossil Pit, Germany, 1987
Age: 47 million years
Location: Senckenburg Natural History Museum, Frankfurt

The French famously call it the little death. But for this pair of mating turtles, the little death became a big death. As they sank down into the depths of a lake in their post-coital bliss, they reached toxic waters and perished. Their fossil remains leave no doubt that they died in the act of mating.

Around 30 fossils of mating insects have been found, most of them caught in amber. But the turtles, Allaeochelys crassesculpta, are the first ancient vertebrates to be caught in the act. 


Discovered: South Majiashan, China, 2011
Age: 248 million years
Location: Anhui Geological Museum, China

Birth is a dangerous process, and for this very ancient ichthyosaur mother it went terribly wrong. She was carrying at least three offspring. One was found under the mother's body. The third was still inside her, waiting to be born. And the second was half-way out of the birth canal, making this fossil unique.


Discovered: Solnhofen, Germany, 2009
Age: 155 million years
Location: Wyoming Dinosaur Center, US

The pterosaur flew just above the water of the tropical lagoon. Snap! It snatched a small, herring-like fish from the water and began to swallow it. But the noise attracted a predator. Up popped Aspidorhynchus, a sleek fish about 60 centimetres long. The fish leaped out of the water and grabbed the pterosaur by its left wing as it was flying. All the animals then splashed down into the water.

But the Aspidorhynchus had bitten off more than it could chew. It didn't have wide jaws and cutting teeth capable of dealing with such large prey.


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