Fossils have been discovered and published in the journal Vertebrate Paleontology, supporting speculation that Microraptor, a Cretaceous theropod dinosaur, was a carnivorous dinosaur.
A rare fossil with perfectly preserved feet of a small mammal has been found inside the skeleton of Microraptor, which is closely related to the origin of birds. In the meantime, it was known that Microraptor consumed fish, lizards, and tree nuts as food, but the carnivorous behavior of eating mammals is the first to be confirmed, drawing attention.
Fossils have been found that can confirm the carnivorous behavior of Microraptor. ⓒNatural History Museum
Finding Traces of the Dinosaur’s Last Meal
It is rare to find traces of the last meal of an already extinct dinosaur on Earth. Even if it is difficult to find traces of living things left as fossils, it is very rare that the food eaten just before death remains undigested. So, of the hundreds of traces of carnivorous dinosaurs discovered so far, only 20 cases have preserved their last meal.
However, traces of prey were recently discovered in Microraptor fossils, and it was recorded as the 21st case that can guess the ‘dinosaur’s last meal’.
Professor Hans Larsson of the Department of Archeology at McGill University in Canada said, “A small rodent or mammalian foot regarding 1 cm long was perfectly preserved inside the Microraptor skeleton.” This discovery, he explained, is the only definitive evidence of the eating behavior of this long-extinct dinosaur on Earth.
Microraptor zhaoianus: IVPP V 12330 Specimen with mammalian feet in the gut contents of Microraptor ©Journal of Vertebrate Paleontology
microraptor, Adding Evidence to Trace the Bird’s Origins
Microraptor is a theropod dinosaur of the early Cretaceous period of the Mesozoic Era, regarding 125 million years ago, and is called a ‘tiny plunderer’ scientific name. It was first discovered in 2000 in Jiufotang, Liaoning Province, China, and appears to have inhabited China.
Academics say that Microraptor is closely related to the origin of birds. It is similar to the size of a crow with a body length of 0.8m and a weight of regarding 1kg, and it has the appearance of a bird with long feathers on all four legs. In addition, although it mainly walks on two legs, it is estimated that it flew between trees with feathers capable of flight.
Such microraptors lived on trees and ate small insects and lizards, but this specimen provided clear evidence that they ate mammals at least occasionally. In addition, the researchers paid attention to the fact that this species was not specialized for a specific prey and did not eat unbalanced, because it had all the feeding characteristics of several species like today’s crows, so it was assumed that it played an important role as a stabilizer in the ecosystem.
On the other hand, the traces of mammalian feet found in this specimen are presumed to have already consumed parts of carcasses that have already been hunted by other dinosaurs or animals. In general, when carnivores consume their prey, they follow a stereotyped pattern, starting with muscle mass and major viscera and moving to areas with little muscle, in this case because they ate parts that were relatively low in nutrients. This suggests that Microraptor occupied the position of a relatively low predator, taking on the role of a so-called ‘carcass scavenger’.
Identification graphic of a Microraptor fossil specimen.
The dark gray color is Microraptor’s rib, the yellow bone is mammalian foot, and the light gray color is unidentified bone. ⓒJournal of Vertebrate Paleontology
However, the research team said that this fossil is unreasonable to define the relationship between Microraptor and mammals as a ‘predator-prey’. This relationship must at least assume direct predatory behavior by the carnivore, and evidence of ingestion through the animal’s bite or visceral contents must be clear. For example, there are traces of bites on the bones of mammals preserved in Microraptor fossils, and on the contrary, interactions that can occur while predating and ingesting prey must be evidence, such as the loss of teeth caused by Microraptor. Unfortunately, however, it was difficult to clarify the behavior of Microraptor as a predator, he added.
Nevertheless, he emphasized that it is clear that this specimen is a rare and valuable material that can record the interactions between Mesozoic theropods and mammals.
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