Four different theropod dinosaurs, showing their teeth and the different shapes of the teeth. (Victoria Arbor / Current Biology)
A long time ago, carnivorous dinosaurs grew small dentures on the back of their teeth called denticles, the best thing to eat prey. While the dinosaurs bit, their food was scraped on the denticles.
Of these small abrasions -the microwear- and the shape of the dentition of dinosaurs, paleontologists say they can say not only what these predators ate, but how they did it, according to a report published in the magazine ] Current Biology on Thursday. A team of researchers in Spain and Canada has examined the spent denticles in 57 fossils of three different dinosaur groups of similar size, Troodon Dromaeosaurus and Saurornitholestes that were about the size of a large swan, as well as a much larger, 9-foot tall tyrannosaur called Gorgosaurus .
Microwar patterns, highlighted in yellow, on the teeth of three theropod dinosaurs. (Angelica Torices and Victoria Arbor / Current Biology)
"We were able to infer that, even if these different dinosaurs had different types of denticles in their teeth, they were biting in the same way, through a 'pinchazo' and pull & # 39 ;. & # 39; system & # 39; said Angelica Torices, paleontologist at the University of La Roja in Spain.
The punch-and-throw maneuver, as the name implies, is a two step movement First a repression with the teeth, then a pull back with the head.This is a very efficient way to obtain food, said Torices.
"As the tooth enters the prey and is pulled back, the tooth will pierce and cut through the soft tissue, "said Domenic D & # 39; Amore, a biologist at Daemen College in New York, who studied the dentition of carnivorous dinosaurs and did not participate in the research." The result is that the meat can be effectively sectioned e a corpse, which is excellent for breaking large vertebrate prey ".
This method of eating has not been extinguished with dinosaurs. The Komodo dragons, the largest living lizards, use it. (The Komodo dragons have the kind of dining etiquette that would connote Emily Post: all chomp, very little chewed.) Unlike the more delicate carnivores, the Komodo dragon requires "minimal input from the jaw muscles. when it kills prey, "says a 2008 study of the eating habits of lizards.
The dinosaurs studied in the new report are a classic image of the prehistoric carnivore, with two legs, long tails and thin forearms. All the types of dinosaurs studied belong to a group of dinosaurs known as theropods. They lived in the Upper Cretaceous period, between 100 million and 66 million years ago. The descendants of the theropod dinosaurs are alive today as birds.
Torices and his colleagues also used an engineering technique called finite element analysis, which allowed them to estimate how dental structure behaved in various scenarios. The researchers modeled, for example, the cutting angles and bite forces that the fangs could withstand.
"Most studies that use theropod teeth to better understand the diet have examined the anatomy of the tooth or the remains of the bones of the prey," said D & # 39; Amore. "This is novel because it uses both anatomy and microwear as an indirect measure of behavior, and I find it very convincing."
Although most of the dinosaurs in the study were about the same size, Torices said that it was likely that animals ate different foods despite the same method of biting. The Troodon teeth would probably yield if the dinosaur bit at a non-optimal angle, suggesting that Troodon avoided the prey that faced it. "The possible food sources could have been small or invertebrate animals or even carrion," he said.
Dromaeosaurus and Saurornitholestes teeth however, could withstand greater stresses. These dinosaurs probably attacked larger prey and could sink their mouths into bones, the scientists concluded.
The giant Gorgosaurus had a structure similar to that of the tooth Dromaeosaurus – except that its fangs were much larger. The fossil evidence in tyrannosaur manure indicates that these large predators chewed bones. His teeth have no wear, unlike hyenas and other modern bone crushers, but Torices said that this can be explained by the fact that dinosaurs replaced their teeth continuously.
"All these dinosaurs lived at the same time and place, so it is important to know if they competed for food resources or if they targeted different prey," said Torices. "Through this work we began to understand a little better the interactions between these predatory dinosaurs and the role of troodontids in the ecosystem."
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