Dinosaur footprints 90 million years old are found – 10/14/2023 – Science

A set of at least ten footprints, from different individuals and even different groups of dinosaurs, was found on a farm in the city of General Salgado, 502 kilometers from the capital of São Paulo.

With an estimated age of 100 to 90 million years ago, the record corresponds to the first discovery of dinosaur footprints from the Late Cretaceous in the state of São Paulo, according to researchers from the Federal University of Uberlândia, UFSCar (Federal University of São Carlos) and from MZUSP (USP Zoology Museum), responsible for the study.

“It’s really an unprecedented find because other footprints from the same basin that have already been described are from another formation, in the state of Paraná, and of a different age”, explains paleontologist Bruno Navarro, a doctoral student at the USP Zoology Museum. “These footprints would be from a different interval and from a different geological context, possibly a river or lake, while the footprints found previously were from a desert environment, with wind action [do vento].”

Navarro participated in the excavation, which took place last month, in the interior of São Paulo. It was necessary to break the rock into three parts to be able to carry each one of them and take them to the MZUSP Paleontology Laboratory, in the south of São Paulo, with each block weighing approximately 100 kg.

The owners of the traits include a theropod dinosaur (a group of bipedal carnivorous dinosaurs, which includes tyrannosaurs, abelisaurs and also the bird lineage), a sauropod (large herbivorous dinosaurs that moved on four legs) and, possibly, an ornithopod (bipedal herbivorous dinosaur).

According to paleontologist and specialist in ichnofossils (as the traces of extinct organisms are called, but which do not represent preserved parts of the animal) Marcelo Adorna, from UFSCar, it is possible to identify the presence of different organisms due to the deformations that each footprint caused in the rock .

“It could be that at least three different animals are represented there, which has a theropod, which is indisputable due to the three clearly visible fingers with a claw, and it could be that there is another that has a more rounded shape, like hooves. [ornitópode], and a third, very circular, which may have been a sauropod offspring. These are interpretations that we make later, in the laboratory”, he explains.

According to Navarro, it is very difficult to establish which species was responsible for each footprint. This is because, without preserved bone elements, the description based on foot anatomy alone is complicated. “We can’t do it in ichnology [área da paleontologia que estuda vestígios de organismos fósseis] associate with a species. We associate with producers, and that’s why we identified three distinct footprint patterns,” he said.

The sediments where the footprints were found are part of the Bauru Basin, where the Cretaceous rocks occur in the interior of the states of Paraná, Minas Gerais, São Paulo and part of Mato Grosso do Sul. The Cretaceous represents the third and final period of the Mesozoic Era and spanned from 145 to 66 million years.

In the same basin, several fossils have already been found, such as crocodiles, chelonians (turtles), birds, snakes and dinosaurs, but this is the first time that scientists have found footprints, and in good condition. However, at the same level where the animal remains were found, there were no fossils preserved.

The footprints were accidentally found by Ariovaldo Giaretta, professor of zoology at the Federal University of Uberlândia (Ituiutaba campus), who was searching for snake fossils in the area — as he had found a snake fossil in rocks of the same age in the area of ​​the basin that is in the Triângulo Mineiro.

“As I knew there was a possible chronocorrelate [rochas de mesmo estrato possuem a mesma idade]I went looking to see if I could find other fossils when I came across this set of footprints which, in itself, drew attention due to its level of preservation and because it was made up of a set of types of dinosaurs”, he said.

The team is now carrying out an accurate analysis of the footprints in the MZUSP Laboratory, which can help indicate, for example, characteristics of the environment. It is likely that those footprints were formed when animals went to the river to drink water.

“By studying the footprints, we were able to establish ecological relationships that bone alone often cannot, as if one of the carnivorous dinosaurs was chasing the herbivores. We will analyze all of this in detail based on the so-called biodeformation, which is the type of pressure under the sediment that led to the printing”, explains Adorna.

Navarro and the MZUSP team intend, in addition to disseminating the scientific study, to take the footprints for display at the museum, which is located in the south of the capital. “In addition, of course, to organizing new collections to look for bones and other footprints that may be preserved at other levels”, says the researcher.