Bicharraco: The dino ‘monsters’ of Patagonia—and the hermit who found them

By Nicholas St. Fleur

 National Geographic 

Published May 22, 2026 

 Deep in the desert of southern Argentina, in a tiny two-room cabin above a small canyon, a lone shepherd turns a radio on each day at noon to hear the regional news. 

A recluse without phone or internet, the little old black radio is Dionide Mesa’s lifeline to the world. 

It delivers personal messages—from traders coming to buy wool or family and friends planning to visit. Twenty years ago, it also brought a paleontologist. 

He had gotten word of the reclusive shepherd in Patagonia who had discovered giant fossilized bones on his ranch—“bicharracos,” as he called them, Spanish slang for “big beasts,” or “strange-looking monsters.”

 “If you want to find him in the middle of the morning, he will not be there. 

You may go in the afternoon, he will not be there,” says Diego Pol, the paleontologist and National Geographic Explorer best known for finding the largest known dinosaur, the titanosaur Patagotitan, in Patagonia.

 “But at noon when the messages are being broadcasted, he’s there waiting.” 

Dionide Mesa, a shepherd who lives in a remote part of the Patagonia Desert, discovered the sauropod fossils at the Cañadón Calcáreo Formation in Argentina. María Agustinho 

In 2005, Pol trekked eight hours into the desert to find Mesa. 

He was eager to excavate the fossils Mesa encountered on his ranch while tending to his flock in the Cañadón Calcáreo Formation. 

The late Jurassic fossil site could offer a glimpse into life on the ancient southern supercontinent of Gondwana. It was the beginning of a more than 20-year partnership between the paleontologist and the shepherd with a talent for finding dinosaur bones.

"Every time we go, he [says], 

‘Oh, I have a new beast for you. I have a new finding,’” says Pol. 

“He never said ‘dinosaur,’ ever. 

These are the ‘bicharracos’ for him..

 Now, more than two decades after that initial meeting, Pol has finally uncovered the identity of Mesa’s monster that first brought him to his cabin in the desert: A 155-million-year-old sauropod, or long-necked, plant-eating dinosaur. 

 Measuring an estimated 65 feet long, this dino was a late Jurassic precursor to the titanosaurs (which were nearly twice as big) that once trampled across South America. 

The team published the new species in April in the journal PeerJ. 

 The new finding may help fill a gap in our understanding of where these sauropods lived during the late Jurassic, and the spot they and their close relatives hold in the evolutionary tree of giant dinosaurs. Pol, who works at the Argentine Museum of Natural Sciences, adds that it’s rare to find a sauropod from this time in the Southern Hemisphere.

 The team also suspects it may be a brachiosaurid, a type of sauropod with longer front legs than back legs (though they did not find its forelimbs or hindlimbs). If so, it would be the first from the Jurassic found in South America. 

The discovery has been a long time coming. It took Pol’s team about 10 years just to get funding to excavate the fossils. 

They dug up most of the bones in 2011 and then in 2018 recovered the rest, including three neck bones. Each visit, Pol alerted Mesa to his upcoming arrival via the radio. 

Mesa, often wearing his signature River Plate football club hat (a team whose games he follows on the radio), would invite Pol and his team into his house to share stories. 

 One of Pol’s colleagues, Alexandra Reutter—a student at the Ludwig-Maximilians-Universität München in Germany who is conducting her doctoral thesis on Mesa’s “bicharraco”—told me about one such visit in 2024.

 Mesa, whom she estimates is in his 70s, greeted her and the team then immediately offered them mate, a South American herbal tea sipped through a metal straw and shared among a group from one cup as a sign of friendship and hospitality. 

As they drank, he told tantalizing tales about the latest “bicharraco” he came across. “He has a good eye,” Reutter told me. “He's able to recognize if something is a bone or just a rock. 

It's prettyssive.”  

Paleontologists begin excavating Dionide’s ‘bicharracos’ in the Patagonian Desert. Carolina Padilla  and Museo Paleontologico Egidio Feruglio 

Over the years, the team recovered more than 40 bones of the sauropod, including huge neck, back, and tail bones, as well as parts of the pelvis and ribs. 

During a later visit to the lab at Museo Paleontológico Egidio Feruglio in Trelew, Argentina, Reutter analyzed the fossils and watched as the technicians chipped away at the hard rock. 

 At first, she thought the dinosaur was a known sauropod called Tehuelchesaurus benitezii. But upon closer examination, she realized there were several glaring differences in the spine, hips, and ribs. 

The variations, particularly in the backbones, she says, were strong enough to declare the fossil as a new species. All that was left was figuring out what to call it. 

And they had the perfect idea in mind. The new dinosaur is named Bicharracosaurus dionidei, after the shepherd who found it and the strange beasts he collected. 

 They discovered fossil remains of a new species.Fuente Museo Egicio Feruglio and La Nacion
 “We wanted to have a name to honor Dionide,” Reutter says. When I asked Pol if he and his team were able to inform Mesa about the discovery, he told me that his colleague and National Geographic Explorer José Luis Carballido had already contacted the radio station.

 “We sent a message saying that our new dinosaur was announced,” says Pol. He’s confident that somewhere in the remote Patagonian 

Desert at noon that day, Mesa heard a broadcast about the “bicharraco” that now bears his name. “For sure, he wouldn't miss any of the radio messages.”