Where there’s joy in a terror bird

Huila Colombia — César Perdomo’s small paleontological museum, La Tormenta, is a work in progress. A bare cement structure built on a windswept platform in the Tatacoa Desert, it offers a panoramic view of shallow, craggy canyons carved from soft mudstone.

Inside the museum, fossils are laid out on tables and shelves. The rest of Perdomo’s collection sits in boxes stacked to the ceiling. Also on-site are a restaurant and several rustic cabins, but weeks can go by without a guest.

Perdomo, 44, is a longtime rancher who, like many people in this region, has collected fossils all his life. The Tatacoa Desert is home to rich deposits of fossils from about 13 million years ago, the height of the Middle Miocene epoch.

The non-avian dinosaurs were long dead by then, and South America was an island continent, not yet connected to North America. It belonged to oversize hoofed mammals like toxodonts, distant relatives of today’s rhinoceroses and tapirs; tall crocodiles that walked on land; thickly armored armadillolike creatures called glyptodonts; and giant, flightless birds known as terror birds, with powerful legs and flesh-ripping beaks.

It was a unique time in geological history when birds enjoyed a glorious role as top predators. About 20 terror bird species have been identified from the fossil record. The smallest were no bigger than dogs, while others reached 10 feet tall. Some hunted by ambushing their prey, while others outran it.

Fossils of terror birds have been found in the southern cone of South America, mostly in Argentina, and also in Florida and Texas. Yet despite a century of intensive explorations by paleontologists, they had never been found in between. Their movements and whereabouts were a mystery until Perdomo decided to build La Tormenta.

As a young boy in the desert, already herding his own goats, Perdomo tagged along with two long-running research expeditions led by Kyoto University, in Japan, and by Duke University, in North Carolina. During the 1980s and 1990s, Perdomo helped the scientists on their annual visits, and in turn learned their digging and preserving techniques. He kept his growing collection of ancient turtle scutes and curved toxodont teeth under his bed. Every so often, his mother threw out his “rocks.”

In the mid-1990s, the foreign paleontologists pulled out of Colombia, fearful of worsening guerrilla and paramilitary activity in the region. “I was excited when they left, knowing that when they came back, I would have new material to show them,” Perdomo said of the researchers. “But they never came back, never.”

Perdomo continued collecting, alone, with no books or references to guide him — just memories from the expeditions. As a grown man, he raised cows and kept bees. He hunted for fossils in the afternoons, when the heat abated. His techniques grew more refined and his finds more intriguing, although most of them stayed under his bed.

Eventually, professional paleontologists did return, but this time they were Colombian. In 2010, Andrés Link of the Universidad de Los Andes in Bogotá started coming with colleagues and students, and raising funds for different projects. A few years later he met and befriended Perdomo. “I couldn’t believe that here was this guy, who at age 8 or 9 went around with the Kyoto and Duke expeditions,” Link recalled. “But he knew where the fossils were.”

Link and Perdomo decided to organize, catalog and display Perdomo’s growing collection, opening it to scientists and anyone else who wanted to see it. In 2019, they began building La Tormenta. Before they were done, a storm whipped through and carried off the museum structure, “like in ‘The Wizard of Oz,’” Link recalled. The fossils were left soaked but salvageable.

They started over. The museum wasn’t yet finished last November when Rodolfo Salas, a crocodile specialist from Peru, came by with Link to check out Perdomo’s bones.

“César and I were sitting there,” Link recalled, when a chunky specimen, about 5 inches long, caught the visiting researcher’s attention. It wasn’t from a mammal, Salas assured his hosts, and it wasn’t from a reptile. The fossil, which Perdomo had collected 15 years earlier while repairing a fence, was the tibiotarsus, or middle leg bone, of a bird. An enormous, powerful bird.

The Tatacoa Desert is flanked by two Andean mountain ranges, the Central and Eastern Cordilleras. During the Middle Miocene, the region was a mostly humid landscape of forests, swamps and rivers. As the Andes began emerging 10 million years ago, the rivers were cut off, and the region dried up. Sediments flowing from the rising mountains created exceptional conditions for fossils.

The fossil beds, known to paleontologists as the La Venta deposits, offer a rare snapshot of South American life before the animals of this formerly isolated world met those of North America in what scientists call the Great American Biotic Interchange. This took place about 5 million years ago, as animals began moving in both directions across the fully formed Isthmus of Panama. Terror birds held on for several million more years before becoming extinct, most likely outcompeted by big cats and canines.

When Link first called about Perdomo’s specimen, Federico Degrange, a paleontologist at Argentine science agency CONICET who is the world authority on terror birds, didn’t need to go to Colombia to know that he was dealing with something remarkable.

From the 3D images that Link sent, Degrange determined that the fossil had come from a bird at least 10% larger than the two biggest cursorial, or running, terror bird species known to date: Titanis walleri, from North America, and Kelenken guillermoi, from Patagonia.

The finding offers a new perspective on the La Venta ecosystem, said Degrange, who is the lead author, along with Link and Perdomo, of a new paper describing the fossil, published in the journal Papers in Paleontology.

“This was an apex predator,” Degrange said. “It preferred open areas. Before this discovery, most of the remains from La Venta indicated that it was a tropical forest environment. This suggests it was instead a mixture of open areas, shrubbery and forests” — much like Southern Argentina during the Middle Miocene.

Siobhan Cooke, a paleontologist at Johns Hopkins University who is also an author on the paper, said the finding “confirms that terror birds were part of the faunal community at La Venta for some time, not something transient.”

For a full week in June, Link’s students and colleagues, visiting from Bogotá, worked to catalog Perdomo’s fossils.

After his fossil was identified as a terror bird late last year, Perdomo remembered something from his childhood: He had seen the fossil skull of what he now realized was a terror bird. One of his second cousins, with the help of a local priest, had dug it out and taken it to the museum in Villavieja.

The professional paleontologists trusted Perdomo’s memory; they had relied on it for years to guide their searches. “If César says he saw a beak, he saw it,” said Cooke, who has worked in the field with Perdomo and Link.

Many older desert dwellers remember the Duke and Kyoto University expeditions with mixed feelings.

But the terror bird skull couldn’t have been taken by the foreign teams, Link concluded, “because if so, they would have published something.”

It seemed futile to try to get to the bottom of what had happened to the terror bird skull. Fossils, even obscure ones, were lost or stolen all the time.

Before the week was over, Perdomo, Link and their colleagues had excavated a beautiful, nearly intact fossil glyptodont from a nearby ranch.

Anyone who wanted to see or work with this fossil, or that of the terror bird, would have to come to La Tormenta, Link noted — not like in the old days, when the good fossils left the country.