August 1, 2021

Discovered a giant ancestor of mammals that rivaled dinosaurs | Science

Discovered a giant ancestor of mammals that rivaled dinosaurs | Science


Excavations in Lisowice (Poland).

A team of paleontologists has discovered the remains of an animal the size of an elephant that lived about 210 million years ago and that by its size and time should not be there. No other species in his group came anywhere near a similar gigantism. It is still a mystery how it became so big just at the time when the ancestors of the greatest known dinosaurs appeared.

The new species has been baptized Lisowicia bojani by its place of origin, Lisowice, south of Poland. Since 2007, a team of Polish paleontologists has recovered more than 1,000 remains of reptiles, amphibians and about 100 bones from at least two specimens of the new species, explains Gregorz Niedzwiedzki, paleontologist at the University of Uppsala (Sweden) and co-author of a study that describes the finding today in the scientific journal Science.

The lisowicia was a synapsid, the large group of reptiles "shaped like a mammal" from which the mammals properly said. "They were not our direct ancestors, but they were relatives, something like the cousins ​​of mammals in the Triassic," explains Niedzwiedzki.

These animals fed on plants and had already developed upright legs like those that later characterized mammals and animals. dinosaurs. The largest synapsids that were known until now measured about 3.5 meters and did not reach two tons. That is why the dimensions of this new species are so surprising: almost five meters long, two and a half meters high and nine tons in weight, a "gigantism" that rivals that of the herbivorous dinosaurs.

The new species is, together with the dinosaurs and their ancestors, the largest four-legged animal that lived in the Triassic (between 250 and 200 million years ago). She is also the last survivor of her lineage. The authors of the finding speculate that perhaps the lisowicia reached such large sizes to maximize food intake and treasure more energy. Another possibility is that being greater than its predators gave it an important survival advantage. Judging by the remains found in the same site the biggest carnivore of that time was the smok, a "robust, bipedal monster, up to six meters long", which belonged to the group of archosaurs (which includes the dinosaurs and whose Current representatives are birds and crocodiles), says Niedzwiedzki. The rest of the dinosaurs present did not reach the meter in length.

The finding of this species shows "that distant relatives of mammals remained dominant in their ecosystems well into the age of the dinosaurs," explains Christian Kammerer, a researcher at the Museum of Natural Sciences in North Carolina. "Until now we thought that these protomamifers disappeared at the end of the Triassic and that only mammals coexisted with dinosaurs, but this finding shows us that the largest specimens also lived at the same time as the largest dinosaurs," he points out.

This same year Kammerer led an investigation into fossil footprints discovered in South Africa in the 19th century. For decades they had been attributed to some type of dinosaur, but he showed that he actually made them a dicyonode, the protomamiferous group that the lisowicia belonged to. According to the work, the path to gigantism of the dicynodonts was gradual and lasted about 20 million years, a time similar to that which took the herbivorous dinosaurs, with which they overlapped in time, and much later, mammals.

Comparison of Lisowicia with an African elephant.
Comparison of Lisowicia with an African elephant.

It is "difficult" to know the reason for its gigantism, but it could also be due to the competition with other smaller herbivorous reptiles to reach the highest vegetation, Kammerer adventure. Right from 210 million years ago appeared the sauropods, herbivorous dinosaurs with long necks reaching up to 18 meters high and therefore could reach even higher vegetation. "Maybe that's the reason why these animals were so successful in the next period, the Jurassic, while the dicynodonts [como lisowicia] they became extinct, "he adds.

This new species "represents a fossil out of place and time, which is always of great interest for the history of life", highlights José Ignacio Canudo, paleontologist at the University of Zaragoza. "This finding shows that in the Triassic of Europe there were adequate conditions for the gigantism of a group of synapsids," he explains. Probably another group of much smaller synapsids are the ancestors of current mammals, whose lineage flourished after the extinction of dinosaurs. These animals did not reach sizes as those of lisowicia until 150 million years after its extinction and today it reaches enormous dimensions like those of African elephants and whales.

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