Scientists announced Tuesday the discovery of a new dinosaur in Patagonia, Argentina, with a crocodile bone in the jaw of its skeleton. The discovery is labelled as one of the most complete specimens yet found of the enigmatic megaraptoran group, whose fossil was recovered with the forelimb bone of a crocodile-like reptile pressed against its jaws. Researchers say the find that offers fresh clues about how these predators fed in the final chapter of the age of dinosaurs.
The specimen, named Joaquinraptor casali, was recovered from the Lago Colhué Huapi Formation in Chubut Province, Argentina, and is estimated to be about 7.0 meters (23 ft) long, researchers reported on Tuesday in the journal Nature Communications. The partial skeleton includes portions of the skull, vertebrae, ribs, and limb bones and represents one of the best-preserved megaraptoran skeletons discovered in South America, the team said.
“This fills a major gap by providing one of the most complete skeletons yet,” said Federico Agnolin of the Argentine Museum of Natural Science Bernardino Rivadavia, who commented on the study, even though he was not part of the research team. Lucio Ibiricu of the Patagonian Institute of Geology and Paleontology, a member of the discovery team, noted that megaraptorans are famous for their long skulls and “huge and very powerful claws.”
The dinosaur lived in Argentina 70 million years ago
The dinosaur lived roughly 66 million to 70 million years ago, near the end of the Cretaceous period, and growth-line analysis of leg bones indicates it was at least 19 years old when it died. Among the preserved elements, the researchers highlighted a femur measuring 685 millimeters (27.0 inches). They estimated the animal’s mass at more than 1,000 kilograms (2,205 lb), making Joaquinraptor one of the largest and best-represented Patagonian megaraptorids yet.
Researchers were surprised by the presence of a fossilized crocodile-relative humerus pressed against the predator’s jaws. “The humerus between the jaws is direct evidence that the dinosaur was feeding on large reptiles,” the team wrote, adding that the association suggests megaraptorans may have preyed on, or scavenged, other substantial vertebrates on the humid flood plains they inhabited.
DINONEWS!!!!
Meet Joaquinraptor casali a new Megaraptorid from Argentina that show us more about the anatomy of this peculiar group. So excited to see we have more cranial material from Megaraptor and its relatives.
Article: https://t.co/a9VGkbTKNP#dinosaurs #Argentina pic.twitter.com/7mqJqmTKyu
— The Darknix (@TheDarknix) September 23, 2025
Megaraptorans remain enigmatic. Paleontologists disagree about their place on the dinosaur family tree, however. Some link them to large allosauroid predators such as Giganotosaurus, while others argue they are closer to early coelurosaurian theropods related to tyrannosauroids. The Joaquinraptor’s newly recovered skull and forelimb bones help fill long-standing gaps in the group’s anatomy and may aid those debates, the researchers said.
Crocodile bone: dinosaur meal or coincidence?
The find was made by a multidisciplinary team from Argentina’s CONICET and several universities, working with colleagues from the Carnegie Museum of Natural History in the United States. The name honors the son of the lead author, Ibiricu, and the valley where the specimen was found. The species name recognizes Argentine geologist Gabriel Andrés Casal for his contributions to regional Cretaceous geology.
Researchers said additional study of the bones, including microstructural and comparative analyses, will be important to determine whether the crocodile humerus was part of the dinosaur’s final meal or a coincidental association. They also noted that the forearm’s features suggest specialized adaptations that may have contributed to the group’s evolutionary success in South America during the end stages of the Mesozoic.
Joaquinraptor, the latest megaraptorid to join the world. 7 meters and a ton in weight. It’s one of the geologically youngest and seems to have had a taste for crocs!
Art by Andrew McAfee at the Carnegie pic.twitter.com/TtTsmNwjY0
— Taylor McCoy 🦖 (@TM9380) September 23, 2025
“Joaquinraptor complements what we know about megaraptorids and pushes the fossil record of these predators closer to the mass extinction event,” said Fernando Novas, a paleontologist not involved with the study. “But many questions remain about their relationships and ecology that further discoveries will need to answer.”
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