A chance discovery inside a long-overlooked fossil has revealed an unexpected chapter in pterosaur evolution.
Around 110 million years ago, two small pterosaurs about the size of modern seagulls were flying over a lake or river, likely searching for food or skimming the water. They were suddenly captured and eaten by a larger predator, either a dinosaur or another pterosaur.
At some point afterward, as the predator moved through the nearby coastal Araripe Basin, it expelled the indigestible remains. These included the pterosaurs’ skulls along with four fish from a later meal.
In 2024, researchers from Brazilian universities examined this fossilized regurgitated mass, which had been stored in a museum collection for decades. Inside, they identified the first known filter-feeding pterosaur species from the tropics. Their findings were published in Scientific Reports.
“It was very unexpected, because fossils from the Araripe region have been studied for decades and almost 30 types of pterosaurs had already been found, none of them filter feeders. We didn’t expect to find a new family for that region,” says Rubi Vargas Pêgas, who is conducting postdoctoral research at the Museum of Zoology of the University of São Paulo (MZ-USP) in Brazil with a fellowship from FAPESP.
These filter-feeding pterosaurs had rows of tightly packed, bristle-like teeth. This structure allowed them to strain small organisms such as crustaceans from the water. Because of this feeding style, they are usually associated with freshwater environments, not coastal settings like the Araripe Basin at that time.
A Species Out of Place
The unusual fossil helps explain why Bakiribu waridza, meaning “comb mouth” in the Kariri language, appeared in this region. Today, the Araripe Basin spans parts of three Brazilian states: Piauí, Ceará, and Pernambuco. Even so, it is relatively small, stretching about 160 kilometers (about 99 miles) east to west and 30 to 50 kilometers (about 19 to 31 miles) north to south.
“It was therefore an environment surrounded by others that weren’t necessarily preserved in the fossil record. This species might never have been known if it hadn’t been regurgitated in Araripe, known for the preservation of its fossils,” adds Pêgas, who completed an internship at the Beipiao Pterosaur Museum in China, also with a scholarship from FAPESP.
The fossilized vomit, known as a regurgitallite, shows clear signs of digestion. The pterosaur bones are partially worn by stomach acids, while the four fish remain well preserved, suggesting they were eaten shortly before being expelled along with the Bakiribu remains.
Clues About the Predator
Paleontologist Aline M. Ghilardi, a professor at the Federal University of Rio Grande do Norte (UFRN) who led the study, focused on how the remains were arranged. All the specimens point in the same direction.
“Today’s fish-eating birds swallow animals whole by the head to avoid choking on fins. Whoever ate the Bakiribu and the fish probably did so in the same way, since they are all oriented in the same direction,” she explains.
The leading candidate for the predator is a spinosaurid dinosaur such as Irritator challengeri. These animals were among the few fish-eating species in the region known to consume pterosaurs, and they were large enough to hold all the remains found in the fossil.
A less likely possibility is a larger pterosaur, Tropeognathus mesembrinus. With a wingspan of about eight meters (about 26 feet), it was big enough to swallow smaller pterosaurs, though this scenario is considered less probable.
Bakiribu waridza belongs to the Ctenochasmatidae family. Before this discovery, members of this group were only known from Europe, East Asia, and southern South America, particularly Argentina. In evolutionary terms, the new species falls between the younger Argentine species Pterodaustro guinazui and the older European genus Ctenochasma.
Rediscovering a Hidden Specimen
The fossil was found in the collection of the Câmara Cascudo Museum at UFRN, which is located outside the Araripe region. Scientific initiation student William Bruno de S. Almeida, supervised by Ghilardi, discovered it while reviewing the museum’s fish fossils.
“Fish are very abundant organisms in the Araripe fossil record, which is perhaps why no one realized that among them was an animal that was still unknown,” suspects Pêgas.
After identifying the specimen as a pterosaur, Ghilardi brought together a team of specialists to study it in Natal. Within a few days, they produced the first draft of the scientific paper.
The fossil is preserved in a rock split into two matching halves. One portion has been transferred to the Plácido Cidade Nuvens Museum of Paleontology at the Regional University of Cariri (URCA) in Santana do Cariri, Ceará.
“We incorporated an ethical and decolonial bias into this work. The transfer ensures the preservation of the piece in its territory of origin,” Ghilardi concludes. He was one of the people responsible for repatriating the Ubirajara jubatus dinosaur to Cariri in 2023. German researchers had previously described the dinosaur based on a fossil obtained illegally in the 1990s.
Reference: “A regurgitalite reveals a new filter-feeding pterosaur from the Santana Group” by R. V. Pêgas, Tito Aureliano, Borja Holgado, William B. S. Almeida, Claude L. A. Santos and Aline M. Ghilardi, 10 November 2025, Scientific Reports.
DOI: 10.1038/s41598-025-22983-3
The research was funded by the São Paulo Research Foundation.
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