Structures dug by prehistoric animals are rare in the Northern Hemisphere. When they reach a few centimeters in thickness and a few meters in length, they are usually defined by paleontologists through adjectives such as “mega”, “giant” or “colossal”. In Novo Hamburgo, a city in the state of Rio de Janeiro, however, one of these shelters is 1.20 meters high, 1.8 meters wide and 18 meters long.
The structure is located inside the Ecoparque da Lomba water park, in the Lomba Grande neighborhood. The owner, Siegfried Fischborn, who has maintained the establishment for 21 years, was intrigued to read an article in the NH newspaper, from Novo Hamburgo, about a paleoburrow identified in the neighboring municipality of Taquara, about two years ago.
The discovery resembled a gap in a rock in the park, which had been infiltrated by drinking water. “At the end of the text, there was a phone number for researchers to get information about the existence of possible paleoburrows”, recalls Fischborn to BBC News Brasil.
Days later, a team from the Paleotocas Project, from the Geosciences Institute of the Federal University of Rio Grande do Sul (UFRGS), went to the site and confirmed that it was a tunnel excavated by a prehistoric animal.
Between 2008 and 2018, researchers from the project have already registered more than a thousand structures of this type throughout Brazil and produced more than 80 scientific works on the subject.
Project coordinator, professor at the Heinrich Institute of Geosciences Theodor Frank explains that paleoburrows are uncommon in Europe and North America due to the geological history of those regions.
“These are areas affected by four glaciations in 600,000 years, which worked as a leveling ground. Traces left by the extinct fauna were consumed by the action of natural agents, if not by human activity”, he analyzes.
To designate them, the term “paleotocas” appeared in Portuguese, a free translation from English paleoburrows. According to Frank, some languages, such as German, do not even have words to define these excavations.
In Rio Grande do Sul alone, paleoburrows were registered in more than 20 municipalities, including Porto Alegre. The capital seems to hold primacy in the correct identification of one of these structures as the work of prehistoric animals.
In 1980, the discovery of tunnels in the vicinity of the Faculty of Agronomy at UFRGS, on the east side of the city, had repercussions in the local press. Heard at the time, residents attributed the excavation to Indians, Jesuits, Farroupilha rebels from the 19th century and even to extraterrestrials.
Workers working on a road project in the vicinity reported having walked for about 30 meters in the opening of the structure and that, at the end, the height reached two meters and the corridor was divided into three tunnels, according to the Folha da Manhã newspaper.
Based on this information, the UFRGS researchers estimate that the opening was 80 centimeters high and 1.5 meters wide.
When studying the paleoburrows, the UFRGS researchers identified three basic size patterns. Most are about 1.3 meters in diameter. The most imposing can reach 2 meters high and 4 meters wide. There is, however, an intermediate profile, 80 centimeters thick.
Altogether, the tunnels inside these structures are more than 40 meters long, but experts estimate that the original width probably reached 100 meters.
“It is common for these structures to be identified when there are road works that require excavations or cuts in the terrain, especially outside large centers. “, says Frank.
That’s what happened in 2018, in one of the team’s last field trips (with the new coronavirus pandemic, the university’s adoption of the home office and the lack of funding, these expeditions had to be interrupted).
In Farroupilha, in the Serra Gaúcha, the researchers saw several paleoburrows more than 4 meters high on a wall excavated for the construction of a building. Due to the location, however, it was not possible to explore the interior of the shelter.
Paleontology classifies these and other occurrences as ichnofossils, that is, marks and traces left by animals and plants from other geological times in sediments and rocks.
Just as animals that exist today, such as armadillos, owls and others, dig burrows to protect themselves from predators and shelter their young, specimens of the so-called Pleistocene megafauna, between 2.5 million years and 11,000 years ago, resorted to the same artifice.
Other examples of trace fossils include footprints, claw marks, fossilized feces (coprolites), and so on. The paleoburrows would thus be the largest ichnofossils in existence.
“Our knowledge of the animals that produced these structures has advanced little. We believe that they were made by giant armadillos, which weighed up to 250 kilos”, estimates Frank.
Even these animals, however, would not be able to dig pale burrows between 2 and 4 meters wide. In these cases, says the researcher, most likely they were made by giant sloths that inhabited South America. In many shelters, there are patterned marks on the walls, produced by animal claws.
Geologists, petrologists (rock scholars), paleontologists and archaeologists have numerous resources at their disposal to determine the age of fossils, rocks and human remains.
The exact dating of the paleoburrows, however, is considered impossible, since the terrain in which they were excavated is composed of rocks much older than these shelters.
It is admitted, however, that because they are located close to the surface, they appeared less than 500,000 years ago.
On the 21-hectare property owned by farmer Gilberto Ari Flach, in the municipality of Harmonia, 74 km from Porto Alegre, what was considered for several generations to be a cave was identified in the last decade as a paleoburrow.
“The burrow was already known in my grandfather’s time”, says Flach to BBC News Brasil. Located in an area of ​​difficult access, in a thicket, the structure is filled with drinking water and is not in danger of disappearing.
“Nobody goes there, it’s in the middle of the bush”, explains the farmer, who maintains two aviaries on the property.
To anyone who finds structures similar to paleoburrows, Frank suggests two measures: photograph the site and inform the Paleotocas Project via email [email protected].
