It’s possible that I shall make an ass of myself. But in that case one can always get out of it with a little dialectic. I have, of course, so worded my proposition as to be right either way (K.Marx, Letter to F.Engels on the Indian Mutiny)
The oceans of the Cretaceous of North America teemed with life. Gigantic fish and enormous marine reptiles hunted the Western Interior Sea. A unique new fossil reported today demonstrates rare evidence of direct conflict between these apex predators.
Scientists discovered evidence for this clash of Cretaceous titans tucked away in a specimen drawer in the collections of Chicago’s Field Museum of Natural History. The fossil, a four-meter-long Polycotylus from the Mooreville Chalk of Alabama, held a hidden surprise in one of the bones: a huge tooth embedded in one of the animal’s neck vertebrae.
The specimen was noticed by Professor Christopher Brochu, of the University of Iowa Department of Earth and Environmental Sciences, while taking a break from looking at fossil crocodiles.
“I sometimes look at other material to see if there’s anything I can show in my classes, and that’s when I saw the bitten vertebra,” said Brochu.
The violence of the bite, partnered with millions of years of burial, fossilization, and eventual excavation, had left the tooth crushed, broken at base and tip, and embedded inside the bone. The research team turned to technology to help identify the mystery attacker.
The fossil was scanned using computed tomography (CT), a visualization technique that allowed the research team to study the inside of the specimen without damaging it. The fossil was virtually dissected by two University of Tennessee, Knoxville undergraduates, Miles Mayhall and Emma Stalker, who built a three-dimensional model of a tooth from an unexpected culprit: an enormous bony predatory fish called Xiphactinus.
“We sometimes get these fixed ideas in our heads about who the top predator in any given environment is and who might rest a rung or two down on the food chain,” said lead author and paleontologist Stephanie Drumheller, a teaching associate professor from the Department of Earth, Environmental, and Planetary Sciences at UT. “This fossil is a good reminder that nature is rarely that cut and dry.”
It was unlikely that the Xiphactinus, as big as it was, was actually trying to eat the Polycotylus. Several famous “fish-within-a-fish” fossils seem to indicate that the predator likes to gulp down smaller fish whole. The embedded tooth could have been the result of the fight instead of a hunt. No matter the original motivation for the bite, its depth and location would have certainly proved fatal.
“Plesiosaurs are famous for their long necks, but those necks come at a price,” said coauthor Professor Robin O’Keefe, of the Department of Biological Sciences at Marshall University. “The trachea, esophagus, major arteries and veins, important nerves; all these organs lie vulnerable to attack. A bite to the neck by Xiphactinus would have certainly proved fatal to this animal, if the Polycotylus was not already dead.”
The dramatic evidence of this attack joins a whole host of other evidence known from Mooreville Chalk. Bite marks attributable from other bony fish, sharks, and marine reptiles are known from these rocks, painting a picture of a dynamic ecosystem with diverse predators targeting all sorts of prey, from other marine animals, to the occasional hapless dinosaur who was washed out to sea, to one another. Taken all together, these fossils suggest that swimming in these Cretaceous seas would have been a risky proposition for even the largest of these ancient marine predators.
The vertebrae fossils and scans of the unfortunate Polycotylus examined in this research, showing the embedded tooth of the Xiphactinus.
A bite to the throat: A probable Xiphactinus attack on a Polycotylus from the Cretaceous Mooreville Chalk of Alabama, U.S.A.
Article Publication Date
12-Mar-2026
Monday, February 23, 2026
New ‘scimitar-crested’ Spinosaurus species discovered in the central Sahara
The first indisputable evidence of a new species of Spinosaurus in over a century belongs to S. mirabilis, named for its scimitar-shaped crest and found at a locality far from the ocean’s edge
A new paper published in Science describes the discovery of Spinosaurus mirabilis, a new spinosaurid species found in Niger. A 20-person team led by Paul Sereno, PhD, Professor of Organismal Biology and Anatomy at the University of Chicago, unearthed the find at a remote locale in the central Sahara, adding important new fossil finds to the closing chapter of spinosaurid evolution.
Eye-catching anatomy
The scimitar-shaped crest of S. mirabilis was so large and unexpected that the paleontologists initially didn’t recognize it for what it was when they plucked it and some jaw fragments from the desert surface in November 2019. Returning with a larger team in 2022 and finding two additional crests, they realized the novelty of the new species they had unearthed. Based on the crest’s surface texture and interior vascular canals, the experts believe the crest was sheathed in keratin. They reckon that this display feature was brightly colored in life, curving toward the sky as a blade-shaped beacon.
Another striking feature of the skull is its interdigitating upper and lower tooth rows, which make a deadly trap for slippery fish. Interdigitating teeth, where those of the lower jaw protrude outward and between those of the uppers, is a time-honored adaptation among fish-eaters in the fossil record — including aquatic ichthyosaurs, semi-aquatic crocodile and airborne pterosaurs. Among dinosaurs, it sets Spinosaurus and closest kin apart.
“This find was so sudden and amazing, it was really emotional for our team,” Sereno said. “I’ll forever cherish the moment in camp when we crowded around a laptop to look at the new species for the first time, after one member of our team generated 3D digital models of the bones we found to assemble the skull — on solar power in the middle of the Sahara. That’s when the significance of the discovery really registered.”
Far from shore
Previously, spinosaurid bones and teeth had only been found principally in coastal deposits not far from the shoreline, leading some experts to hypothesize recently that these fish-eating theropods may have been fully aquatic, pursuing prey underwater.
However, the new fossil area in Niger documents animals that were living inland, some 500-1000 km from the nearest marine shoreline. Their proximity to intact partial skeletons of long-necked dinosaurs, all buried in river sediments, suggest they lived in a forested inland habitat dissected by rivers.
“I envision this dinosaur as a kind of ‘hell heron’ that had no problem wading on its sturdy legs into two meters of water but probably spent most of its time stalking shallower traps for the many large fish of the day,” Sereno said.
A remarkable expedition to Niger
The journey that culminated in this remarkable discovery started with a single sentence in a monograph from the 1950s, where a French geologist mentioned finding a single sabre-shaped fossilized tooth resembling those of the giant predator Carcharodontosaurus found in Egypt’s Western Desert at the turn of the last century.
“No one had been back to that tooth site in over 70 years,” Sereno mused. “It was an adventure and a half wandering into the sand seas to search for this locale and then find an even more remote fossil area with the new species. Now all of the young scholars who joined me are co-authors on the report gracing the cover of Science.”
The team ended up meeting a local Tuareg man who led them on his motorbike deep into the center of the Sahara, where he had seen huge fossil bones. After nearly a full day of travel with no shortage of doubts regarding the success of the effort, he led them to a fossil field. There, with little time to spare before returning to camp, the team found teeth and jaw bones of the new species of Spinosaurus.
“I was attracted to the Sahara like a magnet once I set foot there 30 years ago,” Sereno said. “There’s nowhere else like it. It’s as beautiful as it is daunting.” After excavating more than 100 tons of fossil finds, he says of the Sahara, “If you can brave the elements and are willing to go after the unknown, you might just uncover a lost world.”
This latest discovery adds to Niger’s rich legacy in paleontology and archaeology, both of which Sereno has engaged. He has led an international award-winning effort to build the world’s first zero-energy museum, the Museum of the River, on an island in the center of Niger’s capital city of Niamey. It will showcase their world class patrimony that documents Africa’s lost world of dinosaurs, now including an astonishing spinosaur species, as well as stone-age cultures that once lived in a Green Sahara.
“The local people we work with are my lifelong friends, now including the man who led us to Jenguebi and the astonishing spinosaur. They understand the importance of what we’re doing together — for science and for their country,” Sereno said.
Envisioning Spinosaurus mirabilis with multimedia science and paleoart
Back home in Chicago, Sereno’s team at his South Side Fossil Lab in Washington Park cleaned and then CT scanned the teeth and bones, assembling a digital skull rendering for the research report. Using that rendering, Sereno worked with paleoartist Dani Navarro in Madrid to create an action scene involving flesh reconstructions of the new species tussling over a coelacanth carcass. Navarro went farther, creating a detailed 3D physical model of S. mirabilis by adding flesh over a skeletal reconstruction.
Other paleoartists in Chicago (Jonathan Metzger) and Italy (Davide la Torre) animated Nararro’s model, bringing back to life the action behind the scene chosen for the cover of Science. More adept programs, cameras and drones have revolutionized visualization in paleontology as practiced today in the field and lab.
Inspiring young minds
As part of these reconstruction efforts, the team also prepared a replica of the newly discovered skull and a touchable, colorful model of the scimitar crest.
On March 1, in the wake of the Science paper, both replicas will join Sereno’s previous Dinosaur Expedition exhibit at the Chicago Children’s Museum, where kids will be among the first to get up close and personal with this latest dinosaur find.
“Letting kids feel the excitement of new discoveries — that’s key to ensuring the next generation of scientists who will discover many more things about our precious planet worth preserving,” Sereno said.
“New scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation” was published in Science in February 2026. Co-authors are Paul C. Sereno, Daniel Vidal, Nathan P. Myhrvold, Evan Johnson-Ransom, María Ciudad Real, Stephanie L. Baumgart, Noelia Sánchez Fontela, Todd L. Green, Evan T. Saitta, Boubé Adamou, Lauren L. Bop, Tyler M. Keillor, Erin C. Fitzgerald, Didier B. Dutheil, Robert A. S. Laroche, Alexandre V. Demers-Potvin, Álvaro Simarro, Francesc Gascó-Lluna, Ana Lázaro, Arturo Gamonal, Charles V. Beightol, Vincent Reneleau, Rachel Vautrin, Filippo Bertozzo, Alejandro Granados, Grace Kinney-Broderick, Jordan C. Mallon, Rafael M. Lindoso and Jahandar Ramezani.
Fossilized head crests of S. mirabilis were among the researchers’ first finds in the remote fossil area they call Jenguebi. Photo by Daniel Vidal.
Credit
Photo by Daniel Vidal
With only a few hours to spend after discovering the remote fossil area Jenguebi in November of 2019, Spanish paleontologist
Dan Vidal hovers over a quickly gathered collection of fossils, which included the crest and jaw pieces of a new scimitar- crested spinosaurid Spinosaurus mirabilis (photograph by Paul Sereno)
Credit
`Photograph by Paul Sereno
Paul Sereno poses with reconstructed skull of Spinosaurus mirabilis. Photograph by Keith Ladzinski.
Credit
Photograph by Keith Ladzinski
A single Spinosaurus mirabilis rears over a carcass of the coelacanth Mawsonia on the forested bank of a river some 95 million years ago in what is now the Sahara Desert in Niger. A scimitar-shaped head crest and interdigitating teeth characterize this wading giant, one of the last-surviving species of a spinosaurid radiation some 50 million years in the making (artwork by Dani Navarro)
New scimitar-crested Spinosaurus species from the Sahara caps stepwise spinosaurid radiation
Article Publication Date
19-Feb-2026
Saturday, January 24, 2026
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
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 atrevistapesquisa.fapesp.br/en/dinosaur-fossil-to-be-returned-to-brazil/).
