An international team of paleontologists announced the discovery of a 70-million-year-old carnivorous crocodile, Kostensuchus Atrox, in a study published in the open-access journal PLOS ONE. The first crocodyliform found in Argentina’s Maastrichtian-age Chorrillo Formation and one of the most complete peirosaurids yet described, the find is revealing a hypercarnivorous apex predator that helped define late Cretaceous ecosystems of southern Patagonia.
The specimen was discovered in March 2020 at Estancia Anita near El Calafate, Santa Cruz, embedded in a rock concretion and including a complete skull and much of the skeleton. While walking the plains, members of the expedition noticed a heavy rock block that showed hints of a crocodilian skull. The discovery was made by an international team that included Argentine scientists Fernando Novas and Diego Pol and Japanese scientists Makoto Manabe and Takanobu Tsuihiji.
The animal was not a dinosaur but a peirosaurid crocodyliform, an extinct group related to modern crocodiles and alligators. Researchers identified it as a large, largely terrestrial carnivore that lived along riverbanks and floodplain forests in a warm, seasonally humid landscape. The Chorrillo Formation represented a temperate, humid environment with rivers, lagoons, and vegetation, and the broader area also yielded fossils of fish, frogs, turtles, snakes, plesiosaurs, insects, plants, and small mammals.
The remains indicated a broad, power-built skull and a wide jaw lined with more than 50 sharp, serrated teeth, some over 5 centimeters long—features that signaled hypercarnivory and an ability to slice through muscle and bone, likely including medium-sized dinosaurs, reported New Scientist. “The back end of its lower jaw suggested it had massive jaw-closing muscles and one of the most powerful bites of its ecosystem,” said Pol, at the National Council for Scientific and Technical Research in Buenos Aires, Argentina. “Unlike modern crocodiles, which have long, flat snouts, Kostensuchus had a high, wide and extremely robust skull built for sheer power,” said Pol.
Based on comparisons with complete alligator and caiman skeletons, fossil bones indicated Kostensuchus likely reached around 3.5 meters in length and about 250 kilograms in mass, placing it among the top predators in its ecosystem and comparable in size to a Siberian tiger. The genus name combined Kosten, meaning wind in the Aonikenk/Tehuelche language, with suchus, a reference to the Egyptian crocodile-headed god Souchos, while the species name atrox meant fierce in Latin.
Multiple lines of evidence pointed to a predominantly terrestrial or semi-aquatic lifestyle with adaptations for active hunting. “Their body proportions and skull shape suggested they could move better on land and may have hunted on land too,” said Pol. Another indicator was that its nostrils were located at the front of the snout, not on top of the skull, an arrangement that meant Kostensuchus could not breathe and keep most of its body submerged at the same time.
Kostensuchus Atrox was identified as a top predator capable of hunting animals of different sizes, including small and medium dinosaurs, and it was the second-largest predator known from the Maastrichtian Chorrillo Formation, reported Newsweek. In that landscape, megaraptors were seen as major hunters but faced competition from this apex predator in the forests of southern Argentina just a few million years before the end of the Cretaceous. “It would have been one of the greatest hunters of the late Cretaceous Period and the study of the remains we found gave us previously unpublished details about the predators of that time,” said Novas, of the Bernardino Rivadavia Natural Sciences Argentine Museum.
The Chorrillo Formation became a key point for reconstructing Cretaceous life in Patagonia, with dinosaurs such as Maip Macrothorax, Nullotitan Glaciares, and Isasicursor Santacrucensis, alongside a long-necked giant titanosaur. The discovery added to evidence that during the Cretaceous, South American crocodiles coexisted with dinosaurs in a wide range of forms, from aquatic to terrestrial, including predators and herbivores, and that terrestrial crocodiles from different lineages regularly grew large enough to challenge big predatory dinosaurs.
The completeness of the specimen revealed for the first time, according to the researchers, the anatomy and body plan of a large, broad-snouted peirosaurid. Such peirosaurids were likely top predators, as indicated by several predatory adaptations and large body size, they explained. The new crocodyliform increased the predatory component of terrestrial ecosystems at high paleolatitudes by the end of the Cretaceous, they wrote.
Written with the help of a news-analysis system.