Paleontologists have discovered the fossilized remains of a crocodile "hypercarnivore" that lived in what is now Argentina some 70 million years ago -- and it ate dinosaurs.
Named Kostensuchus atrox, the species lived during the Maastrichtian age at the very end of the Cretaceous period, just before the extinction of the dinosaurs.
At that time, southern Argentina was a warm, seasonally humid landscape made up of freshwater floodplains, home to creatures like dinosaurs, frogs frogs and various mammals.
The skeleton of K. atrox was found largely intact, and included a well-preserved skull and jaws. Researchers who described the find believe that it likely grew to some 11.5 feet long and weighed in at around 550 pounds.
It had a wide, powerful jaw and big teeth that made it capable of devouring large prey -- including, the team suggest, medium-sized dinosaurs -- positioning it as one of the top predators in its ecosystem.
The name of the new genus in which the species has been placed was inspired by the Patagonian wind known in the native Tehuelche language as the "Kosten", and the Egyptian crocodile-headed god known as "Souchos". The species name of "atrox", meanwhile, means"fierce" or "harsh".
K. atrox is the first crocodyliform fossil found in the roughly 70 million-year-old Chorillo Formation of rocks that outcrops in Southern Argentina -- and one of the most complete specimens of the extinct peirosaurid crocodyliform group, which are related to modern-day crocodiles, as well as alligators.
Its discovery, say the researchers, provides new insights into the diversity and the ecological dynamics of the period.
Dinosaurs whose fossils have been unearthed from the Chorrillo Formation include a long-necked, giant-sized and aptly-named "titanosaur" and a 10-foot-long bipedal plant-eater known as Isasicursor santacrucensis, among others.
Modern crocodiles can grow bigger than their newly discovered prehistoric relative. The saltwater crocodile, the largest crocodile species and reptile in the world, can grow up to 23 feet and over 2,000 pounds.
With an average of 66 teeth that can measure up to five inches long, it also has the greatest bite pressure of any other animal in the world.
It can also hold its breath underwater for long periods of time, making it one of the most dangerous predators both on land and in the water.
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Reference
Rozadilla, S., Agnolín, F., Manabe, M., Tsuihiji, T., & Novas, F. E. (2021). Ornithischian remains from the Chorrillo Formation (Upper Cretaceous), southern Patagonia, Argentina, and their implications on ornithischian paleobiogeography in the Southern Hemisphere. Cretaceous Research, 125. https://doi.org/10.1016/j.cretres.2021.104881
Novas, F. E., Pol, D., Agnolín, F. L., Carvalho, I. d. S., Manabe, M., Tsuihiji, T., et al. (2025). A new large hypercarnivorous crocodyliform from the Maastrichtian of Southern Patagonia, Argentina. PLOS ONE, 20(8). https://doi.org/10.1371/journal.pone.0328561