A scientific discovery in Chile is rewriting the evolutionary history of Patagonia.
It concerns a small fossil tooth found in the Sierra Baguales that revealed the oldest placental mammal in the south of the country.
This creature from 40 million years ago weighed about 200 kilos and resembled a mix between rhinoceros, hippopotamus, and tapir.
Incredible scientific discovery in Chile: the molar that tells millions of years of history
Specifically, the fossil corresponds to Albertogaudrya unica, an herbivorous mammal of the order Astrapotheria.
This species inhabited the southernmost region during the middle to early late Eocene.
The scientific discovery in Chile extends the known distribution of this species by more than 400 kilometers south.
Previously, samples of this had only been found in Chubut (Argentina) and Aysén (Chile).
“The most interesting thing is that, from such a small remnant, like a tooth, we can tell a story from various points of view: biological, geological, and evolutionary,” explains Juan Enrique Bostelmann.
Bostelmann is the paleontologist responsible for the Paleontology and Biocronology Unit of the Servicio Nacional de Geología y Minería (SERNAGEOMIN) and leader of the research.
The lower molar was recovered in estuarine deposits of the Río Turbio Formation, in the Magallanes Region.
These sediments marked the mouth of rivers in a coastal system that existed about 40 to 37 million years ago.
The incredible extinct giant mammals that lived only in South America
The astrapotheres were large and strange mammals, exclusive to South America.
“It was a herbivorous animal of about 200 kilos, larger than a tapir, but smaller than a bull,” notes Bostelmann.
“If we saw it today, it would look like a strange mix between a rhinoceros, hippopotamus, and tapir,” he exemplifies.
However, he clarifies that “one should not be confused,” as the Albertogaudrya unica “belongs to a group of exclusively South American animals, extinct millions of years ago.”
Despite being an iconic species of the Eocene, its fossil record is very scarce: only a few teeth and jaw fragments are known.
“Even in Argentina, where these animals were first described in the 19th century, the findings can be counted on the fingers of one hand,” added the scientist.
The scientific discovery in Chile allows reconstructing prehistoric environments
Another point to highlight is that the fossil was discovered in an environment that, although now Patagonian, was very different at the time.
“Temperatures were higher, with a subtropical vegetation and wide coasts,” explained Bostelmann.
In the past, “in the fossil-bearing rocks of the Río Turbio Formation, remains of sharks, crocodiles, and other aquatic animals have been found.”
Thus, this tooth is one of the few terrestrial vestiges found in the area, helping to visualize how the Patagonian coastline was formed 40 million years ago.
The discovery also allowed for the precise dating of the fossiliferous levels of Sierra Baguales and offers information on the environmental transition between marine and continental ecosystems during the Eocene.
“For this period, 40 million years ago, we really know very little about the mammals of southern Patagonia,” marked the scientist.
And he added: “This discovery allows us to suggest some spatial links with other areas of central-northern Patagonia.”
