Prehistoric crocodile that hunted dinosaurs on land discovered in Argentina after 66 million years

Scientists in Argentina have discovered a new species of ancient crocodile that lived at the same time as the last dinosaurs. The fossil, found near El Calafate in Patagonia, includes a nearly complete skull and jaws, giving researchers their clearest look yet at this group of extinct reptiles known as peirosaurids. It grew up to 3.5 meters long, weighed around 250 kilos, and used its sharp, serrated teeth to slice through meat, making it one of the top hunters of its time, a ‘hypercarnivore’ predator that lived almost entirely on meat.


The study, led by paleontologists from Argentina’s Museo Argentino de Ciencias Naturales (MACN) and an international team of researchers, describes the predator as Kostensuchus atrox. This study was published on PLOS ONE on August 27.

Kostensuchus atrox, a name rooted in mythology

The newly described species, Kostensuchus atrox, carries layers of meaning in its name. “Kosten” comes from the Aonikenk (Tehuelche) word for the fierce Patagonian wind, while “suchus” is drawn from Souchos, the crocodile-headed Egyptian god Sebek. The species name atrox translates from Greek as “harsh.” Beyond being a new species, Kostensuchus also represents a brand-new genus, making it a significant addition to the crocodyliform evolutionary tree.

The most complete Peirosaurid yet

Peirosaurids, extinct cousins of modern crocodiles, lived only during the Cretaceous in South America, Africa, and Madagascar. Until now, most finds were limited to fragments such as isolated teeth or pieces of jaw. The new fossil, discovered near El Calafate in Argentina’s Chorrillo Formation, preserves an articulated skeleton with skull and forebody, offering the best example of its kind ever found.

Unlike today’s crocodiles, which lurk in rivers to ambush prey, K. atrox was built for hunting on land. At 3.5 meters long and weighing 250 kilos, it had strong shoulders, a robust skull, and serrated teeth designed for slicing through flesh rather than gripping. This suggests it actively hunted and overpowered prey, from medium-sized herbivorous dinosaurs to smaller carnivores that roamed late-Cretaceous Patagonia.

Filling a Gap in Cretaceous Ecosystems

The discovery helps paint a richer picture of Patagonia just before the asteroid impact 66 million years ago, according to newatlas. Dinosaurs may have been dominant, but predators like K. atrox shared the top of the food chain. Scientists say the fossil expands knowledge of peirosaurid anatomy, showing how these reptiles evolved in parallel with baurusuchids, another group of apex crocodyliform predators in Gondwana.