Fossilized vomit reveals first filter-feeding pterosaur in the tropics

A flying relative of dinosaurs, Bakiribu waridza (“comb mouth” in the Kariri language) filtered crustaceans and other small organisms from rivers and lakes, where it was likely swallowed by a predator that regurgitated it in the Araripe Basin in Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo

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About 110 million years ago, two small pterosaurs, each about the size of a seagull, were flying over a lake or river, looking for food or perhaps bathing, when they were devoured by a large dinosaur or pterosaur. Later, when the predator passed through the Araripe Basin, a coastal region nearby, it regurgitated the least digestible parts of the pterosaurs – their skulls – as well as four fish that it had swallowed in a later meal.

In 2024, a group of researchers affiliated with Brazilian universities found the first species of filter-feeding pterosaur in the tropics in this vomit, which had been fossilized and stored in a museum for decades. The study was published in the journal 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.

Filter-feeding pterosaurs had fine, bristle-like teeth that were very close together. They used these teeth to filter small aquatic organisms, such as crustaceans. For that reason, they were linked to freshwater habitats rather than saltwater habitats, such as the Araripe Basin, during that period.

Therefore, the regurgitation helps explain why Bakiribu waridza, meaning “comb mouth” in the Kariri language, was in that region. The Araripe Basin is now part of three Brazilian states: Piauí, Ceará, and Pernambuco. However, it is a plateau only 160 kilometers long from east to west and 30 to 50 kilometers wide from 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 “regurgitallite,” or fossilized vomit, showed signs of wear on the pterosaur bones due to gastric juices, as well as four well-preserved fish that were likely swallowed shortly before being “returned” with the Bakiribu.

Paleontologist Aline M. Ghilardi, a professor at the Federal University of Rio Grande do Norte (UFRN) who coordinated the study, was particularly interested in the orientation of the remains, all of which were 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 most likely predator was a spinosaurid, such as Irritator challengeri. This was one of the few piscivores in the region that ate pterosaurs and was large enough to hold Bakiribu, the four fish, and other prey in its stomach.

A less likely candidate would be a larger pterosaur, Tropeognathus mesembrinus. With a wingspan of about eight meters, it was the only one large enough to swallow the filter feeders in the region.

Museums

Bakiribu waridza belongs to the Ctenochasmatidae family of pterosaurs. Until now, species of this family had only been found in Europe, East Asia, and southern South America (Argentina). Within the evolutionary tree of pterosaurs, the new Araripe species lies between the more recent Argentine species, Pterodaustro guinazui, and the older European genus, Ctenochasma.

The rock block was found in the collection of the Câmara Cascudo Museum at UFRN, located in a region not part of the Araripe region. Supervised by Ghilardi, scientific initiation student William Bruno de S. Almeida, supervised by Ghilardi, was conducting a survey of the museum’s fish fossils when he came across the pterosaur.

“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.

Upon realizing that it was a pterosaur, Ghilardi assembled a team of experts who examined the fossil in Natal. Within a few days, they wrote the first draft of the published scientific article.

The rock containing the fossil is composed of two mirrored parts. One part was donated 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 (read more at revistapesquisa.fapesp.br/en/dinosaur-fossil-to-be-returned-to-brazil/). 

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Journal

Scientific Reports

DOI

10.1038/s41598-025-22983-3 

Article Title

A regurgitalite reveals a new filter-feeding pterosaur from the Santana Group

 

Canadian scientists uncover hidden cells fueling brain cancer — and a drug that could stop them

McMaster University

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Hamilton, ON (January 21, 2026) – A team of Canadian scientists has uncovered a new way to slow the growth of glioblastoma, the most aggressive and currently incurable form of brain cancer – and identified an existing medication that could treat it.

The research shows that certain brain cells – once thought to simply support healthy nerve function – actually help glioblastoma grow and spread. The researchers discovered that these cells send signals that strengthen the tumour, but when they blocked this harmful communication in lab models, the cancer slowed its growth significantly.

Even more promising, the study suggests that an existing HIV medication could be repurposed to target this process and offer a new treatment option for patients who currently have few. The prognosis for glioblastoma is poor, with survival often measured in months.

The research was published on Jan. 21, 2026 in Neuron and led by scientists at McMaster University and The Hospital for Sick Children (SickKids). Co-first authors of the study are Kui Zhai, a research associate in the Singh Lab at McMaster, and Nick Mikolajewicz, a postdoctoral fellow in the Moffat Lab at SickKids at the time of the study.

“Glioblastoma isn’t just a mass of cancer cells, it’s an ecosystem,” says Sheila Singh, co-senior author of the study and professor of surgery at McMaster University. “By decoding how these cells talk to each other, we’ve found a vulnerability that could be targeted with a drug that’s already on the market,” adds Singh, who is also director of the Centre for Discovery in Cancer Research at McMaster.

It's known that glioblastoma grows by forming a network of cells that communicate and support each other, and disrupting these connections can slow the cancer. This study dug deeper to uncover which brain cells are involved. The researchers discovered that a type of cell called an oligodendrocyte, normally responsible for protecting nerve fibers, can switch roles and actually support tumour growth. These helper cells communicate with cancer cells through a specific signaling system, creating an environment that allows the tumour to thrive. When researchers blocked this communication in lab models, the cancer slowed down significantly, showing that this interaction is critical for glioblastoma’s survival.

What makes this finding especially promising is that the signaling system involves a receptor called CCR5, which is already targeted by an existing HIV medicine called Maraviroc. This means a medication that’s already approved and widely used could potentially be repurposed to treat glioblastoma, offering hope for faster progress toward new therapies.

“The cellular ecosystem within glioblastoma is far more dynamic than previously understood. In uncovering an important piece of the cancer’s biology, we also identified a potential therapeutic target that could be addressed with an existing drug. This finding opens a promising path to explore whether blocking this pathway can speed progress toward new treatment options for patients,” said Jason Moffat, co-senior author of the study, senior scientist and head of the Genetics & Genome Biology program at SickKids.

The breakthrough builds on Singh and Moffat’s 2024 study published in Nature Medicine, which discovered that a migration path used by cells during brain development can be hijacked for cancer cell invasion. Together, these discoveries highlight a new era of glioblastoma research focused on dismantling the tumour’s complex communication networks.

This research work was supported by the 2020 William Donald Nash Brain Tumour Research Fellowship and the Canadian Institutes for Health Research. Singh is a Tier 1 Canada Research Chair in Human Cancer Stem Cell Biology and Moffat is the GlaxoSmithKline Chair in Genetics & Genome Biology at The Hospital for Sick Children.

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Journal

Neuron

DOI

10.1016/j.neuron.2025.12.012 

Article Title

Reactive oligodendrocytes promote glioblastoma progression through CCL5/CCR5-mediated glioma stem cell maintenance

Article Publication Date

21-Jan-2026

 

Bird retinas function without oxygen – solving a centuries-old biological mystery

Neural tissue normally dies quickly without oxygen. Yet bird retinas − among the most energy-demanding tissues in the animal kingdom – function permanently without it. This may be relevant in future treatment of stroke patients.

Aarhus University

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image: 

The pecten is a vascular structure within the vitreous humor of the eyes of birds with a previously unknown function..

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Credit: Aleksandrina Mitseva / Nature

In a study published today in Nature, an international research team reveals how birds have solved a biological paradox. The researchers show that the inner parts of the bird retina operate under chronic oxygen deprivation, relying instead on anaerobic energy production.

At the same time, the study overturns a long-standing assumption about a mysterious structure in the eye that has puzzled scientists since the 17th century.

Most animals supply neural tissue with oxygen through dense networks of tiny blood vessels. This is considered essential, as neurons have an exceptionally high energy demand. The retina, a highly specialized extension of the brain, is no exception – and in fact consumes more energy than any other tissue in the body.

Birds, however, present a paradox. Their retinas are avascular, meaning they lack blood vessels within the retinal tissue itself. This feature is thought to improve visual acuity, since blood vessels scatter light in its path to the photoreceptor. But how the retina survives without a blood supply has remained unknown.

“Our starting point was simple,” says biologist Christian Damsgaard, first author of the study and associate professor at Aarhus University in Denmark. “According to everything we know about physiology, this tissue should not be able to function.”

While the starting point may have been simple, the journey to the end point was anything but simple. It has taken Damsgaard and a growing team of researchers, mostly from Aarhus University, 8 years to produce the results, that are now finally published.

No oxygen where it was assumed to be

For centuries, the prevailing explanation has been that a structure called the pecten oculi – a comb-like, highly vascularized organ protruding into the vitreous body of the bird eye – supplies oxygen to the retina. The structure has been known since the 1600s, but its precise function has remained speculative.

One reason, the researchers note, is that no one had directly measured oxygen levels in the bird retina under normal physiological conditions.

“Doing so is technically extremely challenging,” says senior author Jens Randel Nyengaard, professor at Dept of Clinical Medicine, Aarhus University. “You need to keep the animal under stable, normal physiological conditions while performing very delicate measurements.”

In 2020, the team was able to do exactly that, thanks to a collaboration with veterinary anaesthesia expert and assistant professor Catherine Williams, also from Aarhus University. The results were unexpected: the pecten does not deliver oxygen to the retina at all. Measurements showed that the inner layers of the retina exist in a state of permanent oxygen deprivation, with roughly half of the retinal tissue receiving no oxygen.

Each answer raised new questions

If the retina receives no oxygen, how does it produce enough energy to function?

To answer that question, the researchers embarked on a multi-year investigation combining physiology, molecular biology, imaging, and computational analysis. Progress was slow, in part due to the scale and complexity of the data – and in part due to the COVID-19 pandemic, which restricted laboratory access.

Using spatial transcriptomics, the team mapped the expression of thousands of genes across thin sections of the retina, allowing them to see where specific metabolic pathways were active within the tissue.

(Spatial transcriptomics is a technology that maps gene expression directly within intact tissues, revealing both what genes are active and where they are active).

“We were not looking at one or two genes, but at 5,000 to 10,000 genes at once, each mapped to a precise location,” says Damsgaard. “That gave us a kind of molecular GPS.”

The data revealed a striking pattern: genes involved in anaerobic glycolysis – the breakdown of sugar without oxygen – were highly active in the oxygen-deprived inner layers of the retina.

This finding, however, raised yet another problem. Anaerobic glycolysis produces roughly fifteen times less energy than oxygen-based metabolism per sugar molecule.

“This mismatch raised yet another question: How can one of the most energy-hungry tissues in the body survive on such an inefficient process?” Nyengaard says.

A new role for an old structure

The answer emerged through further imaging studies conducted in collaboration with metabolic imaging specialists. Using radiolabelled sugar and autoradiography, the researchers showed that the bird retina takes up glucose at much higher rates than the rest of the brain.

This led the team back to the pecten oculi.

By revisiting their spatial transcriptomics data, the researchers identified high expression of glucose and lactate transporters in the pecten. The structure, they found, serves as a metabolic gateway: delivering large amounts of sugar into the retina and removing lactate, a waste product of anaerobic metabolism, back into the bloodstream.

“The pecten is not an oxygen supplier. It is a transport system for fuel in and waste out,” says Nyengaard.

The discovery fundamentally changes the understanding of a structure that has been misinterpreted for centuries.

“We are essentially collapsing one house of cards and replacing it with another. House of cards, because scientific findings are not set in stone. New results can add new knowledge. That is how science progresses,” Nyengaard adds.

Evolutionary and medical perspectives

The researchers note that avoiding oxygen and blood vessels in the retina likely confers an optical advantage, improving visual sharpness. Evolutionary evidence suggests that this trait arose in the dinosaur lineage leading to modern birds.

While the study is purely fundamental research, the authors point out that the findings may have broader implications.

“In conditions like stroke, human tissues suffer because oxygen delivery is reduced and metabolic waste accumulates,” says Nyengaard. “In the bird retina, we see a system that copes with oxygen deprivation in a completely different way.”

“Nature has solved a physiological problem in birds that makes humans sick.We hope that understanding this evolutionary solution can inspire new ways of thinking about why tissues fail under oxygen deprivation in disease, and how such diseases can be treated” he adds.

  

The study shows that the pecten supplies glucose to the retina at rates that far exceed the glucose supply rates to the brain, as illustrated on the autoradiography images, showing much higher glucose uptake (pink) in the retina compared to the brain.

Credit

Christian Damsgaard and Morten Busk, Aarhus University / Nature

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Journal

Nature

DOI

10.1038/s41586-025-09978-w 

Subject of Research

Animals

Article Title

Oxygen-free metabolism in the bird inner retina supported by the pecten

Article Publication Date

21-Jan-2026