2013-04-26 12:58:32
125 million years ago, at the beginning of the Cretaceous, dinosaurs ruled the world, as they had been doing since the Triassic, and as they would continue to do for another sixty million years. Until recently we believed that this domain had been complete; that, during all that time, mammals had been little insectivorous and nocturnal animals that lived in fear of large reptiles. But that idea changed a few years ago, when a team of Chinese and American paleontologists discovered the fossil remains of a mammal that had just eaten a dinosaur in the rich Chinese deposits of Yixian.
The Yixian deposits in northeast China are among the richest in the world. From them have emerged, among many others, two species of dinosaurs that are less talked about here: Yutyrannus and the sinornithosaurus. At that time, the region was covered in lakes and forests, and its climate was temperate and humid, with cold winters and a short dry season. From time to time, a volcanic eruption covered the ground with very fine ashes, where the anatomy of many fossil species has been preserved in exquisite detail.
In Yixian there were a wide variety of small feathered dinosaurs, such as Caudipteryx, a peacock-sized omnivore, and Mei long, the size of a duck. Mei long means sleeping dragon in Chinese. It owes its name to the fact that two of the fossil specimens discovered died in their sleep, covered by the ashes of a volcanic eruption. Their posture, with the hind legs folded under the body and the head hidden under one of the front legs, is very familiar to us. It is the same posture that many modern birds assume when sleeping. A new indication of the relationship between dinosaurs and birds.
In Yixian there were also mammals. Almost all fit the traditional image of timid insectivores, but some exceptions have been discovered. Repenomamus robustus is a mammal of half a meter in length and 4 to 6 kilos in weight, more or less the size of a cat, although due to its bulk it is more similar to the Tasmanian devil. It has short legs that are open to the sides, like lizards. Hence its name, Repenomamus means “crawling mammal”. It is a slow, plantigrade animal that walks undulating its body from side to side, like monitor lizards. Since its discovery in 2000, it was supposed to be an omnivore or a scavenger, but a specimen discovered in 2005 changed this hypothesis. The new fossil had inside it the bones of a smaller animal. At first it was believed that it was a pregnant female, but it was soon found that the bones, located to the left side of the abdomen, where the stomach is found in modern mammals, corresponded to a dinosaur: a young psittacosaurus measuring 14 centimeters in length. length. The psittacosaurus is a bipedal dinosaur that could reach two meters in length, a distant relative of Triceratops. The bones found in the stomach of Repenomamus belong to a single individual, and were found whole, some of them still articulated, indicating that Repenomamus ate its prey in large chunks, ripping off its limbs one by one.
In the same excavation that brought to light the remains of Repenomamus robustus with its last prey in its stomach, a new species of the same genus was discovered: Repenomamus giganticus. Repenomamus giganticus is very similar to its relative, but it is even bigger; it is the size of a badger. The skull measures 16 centimeters in length, and the jaws, as large as those of a fox, and with strong muscles, are equipped with carnivore teeth: sharp incisors to hold the prey, canines to kill it, and sharp premolars to tear the flesh. . The molars are small and blunt, useful for crushing but not for chewing plant matter. Repenomamus was basically a carnivore.
The body of Repenomamus giganticus is about one meter in length. The tail is long, more than 35 centimeters. It weighs about twelve or fourteen kilos. As far as we know, it is the largest mammal of the entire Cretaceous period. In fact, it is larger than several contemporary dinosaurs. With his bulk, his musculature and his teeth, he can face dinosaurs bigger than him, if not to hunt them, at least to put them to flight. The dominance of the reptiles was not as absolute as we thought. There was also room for mammalian predators.
FOR SABER FURTHER.
The sinornitosaurus, a poisonous dinosaur
Yutyrannus, the feathered giant
Triceratops, the horned dinosaur
CONSTRUCTION OF GERMAN FERNÁNDEZ:
#Cienciaes.com #large #mammal #eats #small #dinosaur