In the floodplains of southern Patagonia around 70 million years ago, a large predator lurked. Armed with strong jaws and sharp, serrated teeth — perfect for piercing and slicing through flesh — the creature snapped and subdued its prey.
This predator ate dinosaurs, but, perhaps surprisingly, it wasn’t a dinosaur itself. Instead, it was an ancient crocodile relative — a crocodyliform — described by paleontologists and dubbed Kostensuchus atrox in a new study. Discovered from fossils from the Chorrillo Formation in southern Patagonia in Argentina, the species lived in the lead-up to the extinction of the dinosaurs, which were probably one of its primary food sources.
“The discovery of Kostensuchus significantly enriches our understanding of the terrestrial ecosystems that developed along the floodplains,” the paleontologists wrote in their study, published recently in PLOS One. “The new crocodyliform adds to the predatorial component of terrestrial ecosystems.”
Read More: How Crocodiles Have Survived Over 230 Million Years and Two Mass Extinction Events
Argentina’s Apex Predator
Kostensuchus atrox — skull already prepared, freed from the rock.
(Image Credit: José Brusco, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/))
Argentia’s Chorrillo Formation traces back to around 70 million years ago — a warm, wet time in the middle of the Maastrichtian Age of the Cretaceous Period. Back then, freshwater floodplains stretched over the surface of southern Patagonia, serving as a home to theropods, sauropods, and a host of ornithischians — the “bird-hipped” herbivorous dinosaurs that include the ankylosaurs, the hadrosaurs, and many, many others.
“Kostensuchus,” the paleontologists wrote in their study, “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.”
In fact, the predator also shared the landscape with fish, frogs, turtles, and several skunk- and badger-like creatures, though the smaller species in this environment were likely uninteresting to Kostensuchus, which probably targeted larger prey, like the ornithischians.
“The new species was capable of subduing large prey,” the study added, suggesting the species “played the role of a top predator within this end-Cretaceous ecosystem.”
Read More: Prehistoric Crocodile Fossil Shows Species Went Extinct 5 Million Years Later Than Thought
Peirosaurids in Patagonia
Kostensuchus atrox — mounted skeleton (reconstructed 3D print and painted).
(Image Credit: José Brusco, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/))
Discovered around 19 miles from the town of El Calafate, Kostensuchus’s fossils are finely preserved, including a skull, a set of jaws, and an assortment of bones from the body, featuring hip bones, rib bones, even fragments of leg bones. Based on these fossils, the paleontologists believe that Kostensuchus was a 12-foot-long, 550-pound “hypercarnivore” — one of the largest from the Chorrillo Formation, as well as its first crocodyliform.
According to the paleontologists, Kostensuchus is not just any crocodyliform, but a peirosaurid crocodyliform — a particular type of terrestrial reptile that’s related to modern crocodiles and alligators but died in the same extinction event that wiped out the dinosaurs around 66 million years ago.
“The discovery of Kostensuchus,” the paleontologists wrote in their analysis, “provides the first comprehensive insight into the anatomy of large-bodied, broad-snouted peirosaurids that thrived at the end of the Cretaceous.”
Though Kostensuchus’s limbs were longer those of modern crocodiles and alligators, suggesting that the species lived on land, it is possible that it spent some amount of time in water, too. Indeed, Kostensuchus’s anatomy suggests that the species was more mobile than other terrestrial crocodyliforms, with “a wider range of movement” and a “more sprawling limb posture” that might suit “a more aquatic lifestyle,” according to the study.
The fossils of Kostensuchus are thus a treasure trove of information for future study, providing researchers with important insights into the lives and lifestyles of the peirosaurid crocodyliforms that really ruled the world, or at least southern Patagonia, at the end of the Age of the Dinosaurs.
Read More: First Ancient Crocodile Relative from 237 Million Years Ago Was Unearthed in Brazil
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