January 28, 2023

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Microraptor’s last meal was a mammal

A carnivorous dinosaur eating a mammal. A prehistoric drama that took place about 120 million years ago, which took place in an area of ​​only 50 square centimeters. Yes, because the carnivore was a feathered theropod dinosaur, about the size of a crow or crow. The eagle, a mouse-like mammal. Of the hundreds of known carnivorous dinosaur skeletons, only 20 found their last meals preserved. This latest finding, with small-scale subjects in Liaoning Province in northeastern China, now brings the number of cases to 21.

The new study, conducted by McGill University, was published in Journal of Vertebrate Paleontologydescribes the remains of a small fossilized mammal’s feet preserved within the skeleton of a small, feathered dinosaur, Microraptor zhaoianus. The position of the foot is in correspondence with the digestive system of the predator. the microraptorsWe, as we have seen in other discoveries, ate fish and lizards and now we also know small mammals. The discovery indicates that it was a generalist carnivore, a “jack of all trades” in the dinosaur environment.

The well-preserved fossil (center of the photo) is about a centimeter long: it belonged to a small mammal housed inside the skeleton of a feathered dinosaur found in China.
© McGill University

Luminous rarity. “I couldn’t believe it,” says Hans Larsson, a paleontologist at McGill University. inside the rib cage microraptors There was a small mammalian foot similar to that of a rodent: it was about a centimeter long and perfectly preserved. Findings of this kind, like physical evidence of eating a particular food, are exceptionally rare. the microraptors It was completely feathered with wings on its outstretched “arms” and legs. The size of a crow, it is one of the smallest dinosaurs in existence, closely related to the origin of birds.

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“We already knew samples,” Larson continues microraptors Preserved with fish, birds and lizards inside. This new discovery adds a mammal to their diet, indicating that these dinosaurs were opportunists rather than specialists. For the first time we find a generalized carnivore in the ecosystems of dinosaurs. Today we can see that generalist predators, such as foxes and crows, are important ecological stabilizers, because they can also feed on “minor” species subject to sudden population surges, by organizing them.

size issue. Paleontologists consider large theropods (eg t-rexAllosaurus or even me Velociraptor) hunted dinosaurs of a certain size and not mammals which at that time were still very limited in size and therefore not very nutritious. It was different for smaller theropods that could prey on smaller prey, outside of the dinosaur circle.

“Knowing that microraptors It was a generalist carnivore, that is, it targeted prey from different animal classes and orders, offering a new perspective on how ancient ecosystems worked and a possible explanation for the evolutionary success achieved by small, feathered dinosaurs. From them it is believed that various forms of birds appeared. In practice, when there was a Cretaceous CrisisWith the mass extinction, generic species had more chances of survival than those specialized in living in certain environments and eating only certain species.

Decathlon champion. In theory, given his body structure, the microraptors It can hunt small animals by running on the ground, climbing trees, and also by gliding. But, in this particular case, was the rodent eating at the end of real predation? Or did he find it already dead, behaving like a scavenger (that is, consumers of carrion and food scraps left by other species)? In favor of the first hypothesis is the fact that carnivores that do not hunt in groups catch smaller prey than they do. The rodent was ten times smaller than a ferret microraptors. On the other hand, scavengers eat carcasses much larger than their own.

Instead, in favor of the second hypothesis, which is the cemetery of the dead, we consider that the habit of carnivores begins to eat their prey starting with muscles and viscera, and then ending with the less fleshy and cartilaginous parts. The fact that it is in the intestines microraptors Only one foot of the rodent was found, with very little muscle tissue, indicating the ancient scene as a chance encounter with an animal that had already died and may have already been consumed by others. The conclusion to which the researchers are inclined, perhaps not very honorable for a tyrannosaurus, but it demonstrates the most selectiveness of the tyrannosaurus microraptors.