A new study has identified a massive creature that hunted and ate dinosaurs 70 million years ago. It’s called Kostensuchus atrox.
The scholarly article, published on Aug. 27 in the journal PLOS One, reveals that the “crocodyliform specimen,” which is the first of its kind discovered, was recovered in the Austral Basin in Patagonia, near the town of El Calafate in Argentina. Crocodyliforms are the ancestors of modern crocodiles.
The K.atrox belonged to an extinct group of peirosaurid crocodyliforms, according to Live Science.
The massive fossil is advancing knowledge about the ecosystem in the Cretaceous period. According to Live Science, the creature was named for a Patagonian wind called “the Kosten” and “the Egyptian crocodile-headed god Sobek.”
An Expert Says the 11.4-Foot Creature ‘Preyed Upon Dinosaurs’
Researchers have unveiled Kostensuchus atrox, a giant crocodile relative that ate dinosaurs in Argentina 70 million years ago during the Cretaceous period. https://t.co/6JoquL1gUT
— Live Science (@LiveScience) August 28, 2025
The researchers described the creature as “a large predator,” and gave these dimensions:
- It measures 3.5 meters long, which is 11.4 feet.
- It weighed more than 551 pounds.
- The Kostensuchus atrox is larger than similar specimens and indicates that the species evolved into “larger body sizes.”
“In particular, terrestrial crocodylians were notably diverse and abundant during Cretaceous times in South America and Africa, including small and large, meat-eating and plant-eating forms, revealing that these continents were ‘land of crocs,'” Fernando Novas, a paleontologist and the lead researcher, told Live Science.
“These extinct crocodyles competed and preyed upon dinosaurs, and played an important role in the structure of vanished ecosystems.”
The creature had a broad snout that made it likely a “top” predator, the study says, “as evidenced by several adaptations indicative of a predatory lifestyle and its large body size.”
Its “broad, robust snout” covers more than half of its skull length, and it possesses powerful jaw muscles, they wrote. The animal also had “large conical teeth,” they noted, adding that its teeth were capable of “slicing through the flesh of sizable prey.”
The Kostensuchus Atrox was a ‘Large Predator’ Whose Skull & Jaws Were ‘Beautifully Preserved’
The journal article contains many detailed diagrams of the creature’s skeleton and jaw.
The fossil “consists of a beautifully preserved and articulated skull and jaws, and part of the postcranial skeleton that were preserved encased in a large concretion,” the experts wrote.
“The completeness of the new specimen reveals, for the first time, the anatomy and body plan of a large and broad snouted peirosaurid,” added the researchers.
“The end of the Cretaceous Period is particularly well recorded in Patagonia. In recent years a large collecting effort has resulted in a high number of new vertebrate records in different basins of Patagonia,” they wrote.
“Kostensuchus gen. nov. formed part of the latest Cretaceous ecosystem of southern Patagonia, in a freshwater ecosystem under a temperate to warm climate with seasonal humidity, alongside a diverse fauna of dinosaurs, mammals, and other vertebrates,” the researchers added.
“The broad and high snout of Kostensuchus gen. nov., with notably large and robust ziphodont teeth, along with a broad adductor chamber in the skull and deep mandibular ramus, and robust forelimb anatomy suggests that the new species was capable of subduing large prey. These features imply that Kostensuchus gen. nov. played the role of a top predator within this end-Cretaceous ecosystem,” the researchers concluded.
