240 million year old feces! New findings on the origin of the Age of Dinosaurs in the Atacama Desert

A particular amphibian with the appearance of a reptile, the oldest found in the country; fish of which there was no record in Chile and excrements preliminarily attributed to freshwater sharks are part of the discoveries of a group of researchers from the Paleontological Network of the University of Chile, led by paleontologist Rodrigo Otero. The research, published in the Journal of South American Earth Sciences, provides new information about the ecosystem of this area, where remains of primitive forms of reptiles and dinosaurs, among other animals, have also been discovered.

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Cristian Fuentes, Journalist University of Chile.- An area located southwest of the town of San Pedro de Atacama hides a true portal leading to the remote ecosystem that existed at the beginning of the Age of Dinosaurs, when life on the planet was dominated by the first forms of this fantastic group of animals and the first mammals arose. This window into the remote past leads directly to the Triassic, a period between 251 and 201 million years ago, in which all the continents were united and formed a supercontinent called Pangea, where what we know today as the driest desert in the world The world presented a very different landscape.

«The rocks of Cerro Quimal tell us a story with abundant volcanism, but also with a rich plant diversity made up of species from humid environments. These scenarios took place in lake margins distributed from north to south, approximately from San Pedro de Atacama to the southern limit of the Antofagasta Region. This place was located on the southwestern margin of the supercontinent Pangea«, recounts Rodrigo Oteroa researcher at the Paleontological Network of the University of Chile, who led an investigation that revealed new finds from the Triassic in this area, one of the few geological areas in the country with vertebrate fossils from this distant past.

The study, published in the journal Journal of South American Earth Sciencesrevealed the identity of skeletal remains belonging to three individuals of which there was no history in the Chilean paleontological record and whose date is estimated to be close to 240 million yearsin the middle Triassic. Two of them correspond to different forms of freshwater fish, while the third was attributed to a peculiar amphibian, by far the oldest bone evidence found in Chile of this type of vertebrate. In addition to these fossils, the researchers discovered coprolites, that is, feces, the oldest found in the country and the first national record of its kind for the Age of Dinosaurs.

New pieces of the origin of the Age of Dinosaurs

Until now, explains Rodrigo Otero, the record of vertebrates from the remote Triassic in Chile has been scarce and in this study area, in particular, only three forms of archosaurs are known, organisms that inhabited a lagoon environment, with high humidity, and associated with periodic volcanic events.

One of them, the best described to date, is the Chileanosuchus forttae, an armored aetosaur with thick plates on its back and a snout similar to that of a pig. Various studies have related it to crocodiles, although it would have had a mainly herbivorous diet. To this species is added a small and graceful dinosaur of the family Silesauridae, whose size is believed to be close to that of a medium-sized dog, and which stands out as one of the most primitive records of the group of dinosaurs. Finally, the presence of a type of crocodile, possibly a member of Sphenosuchiaa clade that groups together small reptiles characterized by their thin limbs, a feature that gave them a rather strange appearance.

To these records are now added the recent discoveries made known by the team of the Paleontological Network of the U. de Chile, new pieces that add information about the ecosystem of this area 240 million years ago. First, the study “acknowledges the presence of two different forms of freshwater fish of about 25 to 30 centimeters, corresponding to pseudobeaconiids and a form related to Guaymallenia paramillensis. What is interesting is that both types had previously been reported in the Cuyana Basin of Argentina, which is further south latitudinally,” Rodrigo Otero details.

Together with the identification of these fish of which there was no record in the country, the researchers identified a Temnospondyl, a strange reptile-like amphibian, comparable to salamanders, whose length was estimated at about 80 centimeters. “The presence of a temnospondyl in the Middle Triassic is interesting, since this group is underrepresented during that period in South America, which opens up important prospects for new findings of these amphibians,” says the researcher. This animal, which was identified from a skull fragment, also represents the oldest record of an amphibian in the countrysurpassing in 170 million years some frogs that lived alongside dinosaurs in Chilean Patagonia during the Cretaceous.

Oldest record of feces in Chile

Along with the skeletal remains already described, they also recovered fossilized feces with spiral shapes, “which are produced by a limited group of marine vertebrates. Our suspicion is that may correspond to freshwater sharks, considering that in the north of Chile there are records of their teeth both in the Permian and in the Triassic, but that, unfortunately, until now they have not been studied in detail. We hope in future campaigns to be able to find teeth that will allow us greater clarity regarding these findings,” says Rodrigo Otero, who states that it is highly probable that there is more excrement in the place that allows us to add information about the animals that inhabited this area 240 million years ago. years.

According to a researcher from the University of Chile, this record of feces is the oldest in the country and the first described locally within the time period known as the Age of Dinosaurs. “In Chile, only mentions of vertebrate coprolites have been made, but I believe that none of them have so far provided enough information to suggest a producing candidate. This record is the first described in Chile of Triassic age, and the first from a lacustrine environment”. On the other hand, the paleontologist highlights the importance of this type of findings, for example, to determine the diet of the producers of these feces and, through them, learn more about the biodiversity of their environment, something that is possible through the electron microscopy.

A window to the Chilean Triassic past

Cerro Quimal is one of the few places in the country with fossil records from the Triassic, remote period marking a “recovery” of life on Earth after the largest extinction event the planet has ever faced, even worse than the one that ended the Age of Dinosaurs 66 million years ago, where it has been estimated that 95% of life forms succumbed. That is the great importance of this window to the distant past of the Chilean Triassic. “It is during this period that dinosaurs, lizards, turtles, crocodiles and also mammals appear in continental environments.. As for plants, ferns and conifers appear. ‘New’ insects also appear, such as the lineage of grasshoppers, flies and bees and ants. In the sea, meanwhile, the replacement and diversification of forms is explosive”, Otero details.

It further states that several of the locally recognized groups have Triassic “relatives” of enormous sizes in other localities. “For example, there are 6-meter Triassic temnospondyles; and crocodilians like Fasolasuchus could reach 8 meters during the Triassic”. For this reason, he adds, “I think we are just getting a glimpse of what this deposit can tell us. My impression is that this place can hold surprises. Recent campaigns have gone into an increasing number of finds. The geological unit has different levels with bones and they are also relatively abundant, so the potential for future discoveries is very high. Undoubtedly, there will be news regarding the vertebrate record in the near future.”

These discoveries were made in the context of a research project on the vertebrates of Cerro Quimal, led by the paleontologist from the University of Chile Sergio Soto, with the authorization of the Council of National Monuments, and with the support of Project ACT-172099 (ANID -Chile) and the Museum of Natural and Cultural History of the Atacama Desert.

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