'Lost' treasure trove of fossils rediscovered after 70 years

The childhood memories of a landowner in southern Brazil led scientists back to the remnants of a prehistoric wetland that thrived before a major mass extinction.

By Jill Langlois
Published 27 Jul 2022, 10:31 BST
One of hundreds of fossils that was discovered at a site in Dom Pedrito, Rio Grande ...
One of hundreds of fossils that was discovered at a site in Dom Pedrito, Rio Grande do Sul, Brazil, where a wetland ecosystem thrived 260 million years ago.
Photograph by Ferraz et al., 2021

In 1951 two men arrived in Dom Pedrito, a town in southern Brazil, to carry out geological mapping of the pampa, or low grassland. There they found a rocky hill brimming with the remnants of a wetland ecosystem that existed some 260 million years ago.

During the Permian period, when most of Earth’s landmass was still bound up in the supercontinent Pangea, this part of what is now Brazil was covered in vascular plants like horsetails and ferns, and a nearby body of water contained various aquatic creatures. This ecosystem existed shortly before a mass extinction dealt a major blow to life on Earth and set the stage for the rise of the dinosaurs, making the fossil site a significant palaeontological find.

But the researchers didn’t leave a description of the exact location of the extraordinary site they had unearthed, a three-acre patch among about 450 acres of land. So as time passed, and the dirt roads they had followed decades ago were replaced by paved highways that traced different routes, the site was lost to science.

Photographs of the Cerro Chato outcrop in Dom Pedrito, where fossils appear on the surface. The left image was taken in 1951, published by the first researchers to study the site. The right image was taken after the rediscovery of the site.
Photograph by Courtesy of Ferraz et al.

Until now. In a paper published earlier this year, Brazilian palaeontologists announced that the site at Dom Pedrito has been rediscovered at last. Researchers excavating the site say that so far they’ve identified at least six or seven plant species, one species of mollusc, and two fish species; some of the creatures are already known to experts, and some might be new.

“We’ve collected hundreds and hundreds of fossils,” says study coauthor Felipe Pinheiro, a palaeontologist at the Federal University of Pampa. “It’s absolutely amazing. It’s beyond what I’ve ever seen. There’s so much there, it would be impossible to collect them all. The fossils we’ve already found will take decades to study.”

This spectacular site may have stayed in obscurity were it not for the childhood curiosity of Celestino Goulart and his desire to learn more about what was unearthed on his family’s land over 70 years ago.

Through the eyes of a child

When Goulart was a boy, he was fascinated by the rock that sat on his grandfather’s mantle. Embedded in its surface was a fish—or the fossil of one, as he would come to understand as he grew older.

An inquisitive child, he discovered that the fossil came from his own backyard, just outside Dom Pedrito, in the Brazilian state of Rio Grande do Sul. He was 10 years old when he set out to look for more of the curious rocks, walking the rolling hills of his family’s property with his mother.

As it turns out, they weren’t hard to find. “The rocks we found were outcropping,” says Goulart, now 55. After periods of drought, rain had washed away sediments and exposed the fossils. “They practically sprouted up.”

Some of these fossils revealed more ancient fish, while others preserved detailed imprints of the shells of molluscs. But most held fossils of plants, some so well preserved that Goulart says he could see the individual veins spread out like fingers on an open hand across each leaf.

In 2019 Goulart reached out to the city for help with the preservation of fossils on his property. Palaeobotanist Margot Guerra Sommer and geologist Rualdo Menegat, both from the Federal University of Rio Grande do Sul, were sent to the area to get a better understanding of what was there.

Sommer and Menegat had heard of a site in that region described in the 1950s, supposedly rich in plant fossils. When they studied the topography and the types of fossils on Goulart’s property, they began to suspect that this was the lost site—but they needed confirmation.

The two researchers then reached out to Pinheiro, who led a team to collect fossils from the area. On his first trip to the site, Pinheiro found dozens. An expert in vertebrates, he knew he needed help with the preserved plant life, so he called Josilene Manfroi, a palaeobotanist at Vale do Taquari University, and they started going to the site every two months.

Fossil plants collected from the site in Dom Pedrito.
Photograph by Courtesy of Ferraz et al.

Digging up the evidence

As the researchers began to document the fossils, their suspicions grew that this was the same site that had been described in the early 1950s. But it wasn’t until 2021 that Joseane Salau Ferraz, one of Pinheiro’s master’s students in biological sciences, discovered a link.

She was digging through a repository of old scientific journals online, tasked with searching for any existing references to a fossil site on a piece of land belonging to a family named Goulart. Ferraz hadn’t expected to find much, but hidden among the scientific work from decades past, in an annuary from the Brazilian Academy of Sciences, was a six-page article from 1951, written by Emmanoel A. Martins and Mariano Sena Sobrinho.

In it, the two researchers describe a site just outside the town of Dom Pedrito known as Cerro Chato, Portuguese for “flat hill.” On that site was a “recently discovered fossiliferous outcrop … presenting very favourable conditions for stratigraphic observation and containing well-preserved fossils.” The paper mentioned a large area full of fossilised vegetation.

When she realised what she was looking at, Ferraz called Pinheiro right away. “It was a huge surprise,” she says. “It confirmed everything we thought we knew up until that moment.”

With the support of the city of Dom Pedrito and the local universities, the researchers began to dig, slowly removing layers of rock from the hill with a chainsaw and a backhoe. As each level was pealed back, the team went in with hammers and brushes to do the more delicate work of extracting fossils from the rock.

So far, they’ve dug about six feet into the ground, discovering lower levels with even more fossil material than those closer to the surface, including more fish and molluscs, individual scales, and a wealth of ancient plants.

Linking past and present

With government funding, the researchers plan to continue excavations at Cerro Chato for the next three years. Meanwhile, Ferraz has started analysing what they’ve already brought back as part of her master’s thesis.

The fossilised vegetation has been unearthed mostly in pieces, with at least one whole plant. Among the finds are stems and seed clusters from coniferous trees, which recovered quickly from the mass extinction and proliferated in the aftermath. Several pteridophytes—vascular plants that disperse spores instead of producing flowers or seeds—such as ferns, horsetails, and lycophytes, were preserved as well. The lycophytes subgroup, now dominated by species that only grow about a foot tall, included plants that could grow to some 100 feet during the Permian period.

For Ferraz, the ferns have left the biggest impression. “They are so well preserved, you can even see the veins on their leaves, which is something exceptional for this region,” she says.

One fern in particular is helping Ferraz learn more about how these plants spread across the landscape hundreds of millions of years ago. It belongs to the Pecopteris genus and is the first of its kind found in Rio Grande do Sul, possibly representing an entirely new species.

“This is really important,” Ferraz says, “because now we will be able to better understand the distribution of these plants that lived during the Permian period.”

While the Permian has been well documented in places like North America, South Africa, China, and Russia, it hasn’t yet been comprehensively studied in South America. With these newly discovered fossils, the team of researchers hopes to better understand the factors that contributed to the largest extinction event in Earth’s history.

The Permian ended when more than 90 percent of species were wiped out following a series of massive volcanic eruptions in what is now Siberia. This period of runaway warming is particularly important for scientists trying to understand the threat of a sixth major extinction today.

“While what we’re going through now is a result of human behaviour, the mechanisms of extinction are very similar to those that happened during the Permian period,” Pinheiro says. “We are interfering in the same biogeochemical cycles—the carbon cycle, the nitrogen cycle—that during the Permian period, because of natural factors, caused the death of almost 90 percent of species. So when we study this extinction, we’re studying the present day.”

Goulart hopes that the fossil bounty will also help teach those who visit Rio Grande do Sul about the importance of these types of palaeontological sites. He’s already looking into how to turn Cerro Chato into a cultural and educational tourism site to preserve what’s still in the ground.

“When we were kids, we had a few toys related to this type of thing, like most kids did,” says Goulart, one of seven siblings. “But we never imagined then, that right under our noses, in our own backyard, we had the real thing.”

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