The Amazon giant tortoise, which reaches two meters in length, may have been food for humans | Energy and science

Fossil remains of the now-named Amazonian giant tortoise, Peltocephalus Maturin, were discovered around 2015 in a now-defunct mining ravine on the Madeira River, in Rondônia (RO). With the participation of researchers from various countries, including Brazilian universities and the University of the South Pacific, the process of identifying the animal, which is estimated to be between 1.8 and 2 meters in size, has begun.

With the turtle's jaw found, the first hypothesis was that it was Stupendemys, the largest freshwater turtle ever found that lived during the Miocene, about 25 million years ago. It is common in the Amazon region to have sediments and rocks from this geological period, so this was the first assumption, but for scientific proof, researchers sought to date the material.

“We sent some samples to the University of Georgia, where carbon dating researchers work. When the results came back, we saw that it was something much more recent than Stupendemys, so it couldn't be her.” Meanwhile, material about the jaws of Stupendemys was also published, And we saw that they were completely different,” explains Gabriel Ferreira, a researcher at the University of Tübingen in Germany, who led the study. The article was published in the scientific journal Biology Letters.

Food for humans

The dating result indicated that it was between 14 and nine thousand years old. Geological proximity opened the possibility of this species coexisting with humans and also demonstrated the necessity of making comparisons with species living today. Furthermore, it was decided to create a geochemical framework to see if the dating was really reliable.

“This part was carried out by Miriam Pacheco and Marcia Rizzuto, from UFSCar and USP, respectively. They carried out geochemical analyzes to find out how much modification there was in the fossil. With an impressive length of 27 cm, the dentary was analyzed in an unconventional way. Since it is the hardest and lowest part Porosity In the skeleton, tooth enamel is always chosen to be analyzed, but in the absence of that, they had to analyze bone, which is usually the last resource to be used due to its porosity.

Due to the uncertainty of the data, it was decided to set the minimum age of the species at 9,000 years – with the guarantee that it could not be younger than that – and the maximum at 40,000, due to the analysis of plants that were found in less than the fossil that was in it. age. Logically, everything above was newer.

A morphological relationship has been established with the Amazon loggerhead turtle, Peltocephalus dumerilianus. The dentary of this species is characterized by characteristics that also appeared in the fossil, such as the jaw being longer and thinner and ending with a hook, in addition to a unique characteristic of this genus, which is a depression in the lingual part of the jaw. “That's why we called it Peltocephalus as well. We put them in the same species because of these similarities,” explains Gabriel Ferreira.

The Amazon giant, like its closest living relatives, was omnivorous, and its diet consisted of plants and animals. “For example, the Amazon loggerhead turtle eats mainly fruits that fall into the water, and it also preys on some species of snails found in the area. This is its most carnivorous trait, but there are records of stomach contents that show many other remains, such as Crustaceans and snails as well as a lot of plant material, especially fruits and seeds. “So, we think it would be something similar,” the paleontologist says.

The lack of knowledge about the fauna of the area during that period makes it difficult to determine the exact diet of Peltocephalus maturin. The comparison is interesting, but given its size it is unlikely that it fed on small snails like its relative, and even with its size, it should not be a large predator given its slow movement.

Perhaps the Native American civilizations of that period were responsible for the disappearance of this giant species that existed in the region. “The indigenous people of the region use turtles as part of their diet. The oldest records of human occupation in the Amazon are also accompanied by turtle bones. If we can confirm the age and coexistence, and believe in the chronological coexistence between humans and this turtle, then the probability is relatively high that humans preyed on them,” Ferreira also suggests as a hypothesis for the disappearance of Peltocephalus maturin.

“The scientific community has not reached a consensus, but the well-accepted hypothesis is that if there was no human hunting pressure on these giant species, they would still exist,” notes Max Langer, a professor at the University of the South Pacific in Ribeirão Preto who supervised it. search .