While Tyrannosaurus rex ruled prehistoric North America, a different apex predator prowled ancient Argentina: the newly identified megaraptor Joaquinraptor casali.
Image used for illustrative purposes/Chubut Province, Argentina/Lucia Miloro/Unsplash
Paleontologists made a striking find when excavating the dinosaur: clenched in its jaws was an arm bone from a Cretaceous crocodile. This rare fossil offers a possible glimpse into the predator’s last meal, more than 70 million years ago, as told to National Geographic.
“Fossilized behavior is incredibly rare, so when it shows up, it’s worth celebrating,” says Matthew Lamanna, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh and a National Geographic Explorer.
In addition to the skull, Lamanna’s team uncovered the arms, parts of the legs, ribs, vertebrae, and other fragments. They estimate Joaquinraptor measured over 23 feet long and weighed more than a ton. With its elongated snout and stout arms tipped with long, curved claws, it would have been a formidable hunter. The team described the new species Tuesday in Nature Communications.
Despite being known from only a partial skeleton, Joaquinraptor is among the most complete megaraptors discovered. Even more remarkable is the potential meal preserved in its jaws, a rare window into the diet and ecology of extinct predators. Fossilized stomach contents are uncommon but invaluable; past examples include tyrannosaurs with drumsticks and mosasaurs with fish remains.
Unearthing a mystery
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The discovery began in 2019 when Lucio Ibiricu, a paleontologist at Argentina’s Instituto Patagónico de Geología y Paleontología, searched Chubut Province’s Cretaceous rocks for fossils. Colleague Bruno Alvarez spotted a small bone fragment jutting from the rock. When the team returned months later, they uncovered one of their most significant finds.
Skull and arm bones confirmed the fossil was a megaraptor—an enigmatic group of predatory dinosaurs known from Asia, Australia, and South America. Named in 1998, megaraptors were larger than raptors like Velociraptor, featuring long, low snouts and stout arms with large claws. While likely close relatives of tyrannosaurs, megaraptors thrived where tyrannosaurs were absent. Most species are known only from fragmentary remains.
“Megaraptor fossils are usually so damaged that it’s hard to learn much,” says Lamanna. “This one is complete enough to give us a real glimpse, but still leaves questions.”
The earliest megaraptors date back roughly 132 million years, but Joaquinraptor lived near the end of the Cretaceous, between 70 and 66 million years ago—just before the asteroid impact that ended the dinosaur era.
“This discovery highlights that megaraptorids survived right up to the end of the Mesozoic,” says Fernando Novas, a paleontologist who discovered the megaraptor Maip macrothorax but was not part of this team. “It shows these predators were diverse and abundant in South America until the very end.”
Dinosaur’s last supper?
Was Joaquinraptor really feasting on a crocodile when it died? While it’s possible the croc bone ended up in its jaws by chance, the fossil’s context suggests otherwise. The dinosaur’s arm bones were found in near-life position, indicating the burial site wasn’t heavily disturbed by water. No other bones were present nearby, making it likely that the croc was indeed its meal.
“If it’s just coincidence, Mother Nature is playing a cruel joke,” Lamanna jokes.
Novas adds that the find offers a rare snapshot of predator interactions in the late Cretaceous. Interestingly, just last month, Novas and colleagues described a crocodile species named Kostensuchus atrox from roughly the same rock layers—possibly the very species that ended up in Joaquinraptor’s jaws.
