The Cretaceous Carnotaurus was covered in a mixture of thorns and plates that gave it an exotic appearance. Particularly surprising is the lack of the slightest traces of feathers - in recent years, many researchers assumed that almost all late dinosaurs had them.
Scientists have analyzed the remains of the skin, preserved along with the skeleton of the dinosaur Carnotaurus sastrei, found in Argentina. The study showed that the skin was devoid of feathers - while many other dinosaur species were covered in them (feathers facilitated thermoregulation). But the animal was dotted with thorns and plates - and they, apparently, also played an important role in the thermoregulation of this predatory species. Today moloch has similar skin - perhaps the most intimidating looking lizard in the world. A related article was published in Cretaceous Research.
Until the end of the 20th century, dinosaurs were believed to be cold-blooded and covered in scales, like many reptiles today. But in recent decades, a series of discoveries have shown that this is not at all the case: most, if not all of them were warm-blooded. Warm-bloodedness means the need for thermoregulation: it takes a lot of energy to maintain a constant body temperature. This makes sense to reduce heat loss when the air temperature drops and increases on a hot afternoon. Feathers solve this problem quite effectively, which is known for the example of birds - a clade of maniraptors taxonomically related to dinosaurs. Only this group survived the extinction 66 million years ago, and earlier Naked Science told why this happened only to them.
However, new work by researchers from Argentina and Australia shows that feathers were far from the only possible solution to the problem of thermoregulation in dinosaurs. The authors studied the remains of the skin of an eight-meter (long) Carnotaurus, which lived in the territory of modern Argentina about 69-72 million years ago.
"Carnotaurus" means "carnivorous bull." It was a predatory dinosaur with two unusual "horns" over small eyes, which made the discoverers call it "bull". His body length was from 7.5 to nine meters, weight - not less than 1.35 tons. Like the larger tyrannosaurus, the carnotaurs ran on two legs, and the front pair of limbs was small. However, the tiny upper limbs possessed four full toes each.
The creature could inflict bites about twice as strong as the modern alligator, which today remains the leader in this indicator among land animals. The simulation estimated the running speed of the Carnotaurus to be 48-56 kilometers per hour. The function of the supraocular horns is unclear. Due to the powerful musculature of the neck, some paleontologists suggest that these horns were used to deliver powerful blows like rhinoceroses - either to kill victims, or when colliding with other predators or individuals of their own species.
Examination of the skin of a dinosaur has shown that it consists of two types of elements. Large - from 20 to 65 millimeters in diameter - protruding conical scales were combined with smaller (up to 14 millimeters) flat scales that did not overlap each other, separated by narrow strips of connective tissue. Contrary to earlier interpretations, the protruding and flat plates were not ordered in any way. They were randomly distributed over the surface of the predator's body, and in different parts of the skin they looked the same in shape and size.The underlying scales varied just as chaotically in the size and shape of the base.
Moloch in Australia. Depending on the temperature and lighting, it can significantly change its color / © Wikimedia Commons
Researchers believe that some modern species, for example, the Australian moloch lizard, may be close analogues of the device of the outer integument of the carnotaurus. It is also covered with thorns of various sizes, combined with smaller flat plates of scales. Such a peculiar skin allows the lizard of the agamic family to be not only less attractive prey for predators, but also better to get rid of excess heat.
For the Carnotaurus, the latter could also be relevant: running fast in hot climates requires efficient heat dissipation. Bipedality gives an advantage in this sense (an elevated body is better cooled by the incoming air), however, not only predators, but also prey could be bipedal at that time, which left issues of heat removal relevant for carnivorous dinosaurs.