The Middle Miocene of South America was a land defined by dramatic evolutionary experiments and unusual ecological dynamics. Long before the Great American Biotic Interchange allowed North American predators like saber-toothed cats and bears to march southward, South America was an isolated island continent. In this ancient ecosystem, the ratio of mammalian predators to their prey was strangely low. To fill the void at the top of the food chain, giant, non-mammalian reptiles—most notably terrifyingly large crocodyliforms—stepped in as dominant apex predators.
While scientists have long hypothesized that these massive reptiles hunted the enormous, extinct mammals roaming the ancient Neotropics, direct physical evidence of such ancient attacks has remained elusive. Now, a landmark study published in the Journal of Vertebrate Paleontology provides the first definitive fossil evidence of giant crocodylians preying upon and scavenging large mammalian ungulates in the Middle Miocene La Venta fauna of Colombia.
The findings are based on a painstaking examination of four fossilized bone specimens collected over decades from the La Tatacoa Desert in Huila Department, Colombia, a location representing the most diverse and well-sampled fossil vertebrate community in the Neotropics. The fossils—ranging in age from approximately 11.1 to 12.8 million years old—belonged to three distinct species of massive ancient ungulates: Pericotoxodon platignathus, a large, rhino-like notoungulate; and two species of astrapotheres, Xenastrapotherium kraglievichi and Granastrapotherium snorki, which were strange, distant relatives of modern hoofed mammals that sported strange trunks and tusks.
Across these four fossil specimens, researchers identified distinct trace fossils—bite marks, structural punctures, deep drag scores, and catastrophic bone crushing. A partial skull of Pericotoxodon platignathus revealed a massive, circular puncture mark measuring nearly 30 millimeters in diameter on its frontal bone, accompanied by a deeply gouged tooth drag-mark along its snout. A fossilized distal femur of another Pericotoxodon contained a series of semi-circular punctures and shallow pits. Meanwhile, two fossil lower jawbones—one belonging to a Xenastrapotherium and another to a juvenile Granastrapotherium weighing an estimated 1,800 kilograms—exhibited multiple deep puncture holes and severe structural bone crushing.
The primary culprit behind these violent traces is Purussaurus neivensis, a giant relative of modern caimans that grew up to 7 meters in length and weighed nearly two tons. By analyzing the size, conical shape, and distinct keeled vertices of the puncture marks, along with the immense bite forces required to crush fresh mammalian bone, the authors concluded that Purussaurus was the primary predator. Area-based bite force calculations revealed that creating these puncture marks in living, green bone required localized forces exceeding 40,000 to nearly 70,000 Newtons—well within the crushing capabilities of Purussaurus.
“The trace fossils identified here support the conclusion that Purussaurus was the most likely taphonomic agent,” the study’s authors note, highlighting that the close match in shape and size between the giant reptile’s conical anterior teeth and the puncture marks on the ungulate skulls and limbs rules out smaller mammalian or reptilian carnivores. Furthermore, math modeling of “predation zones”—which maps predator body mass against maximum prey size capability—demonstrates that even an 1,800-kilogram astrapothere fell well within the hunting capacity of an adult Purussaurus.
The placement of these bite marks offers fascinating insight into ancient hunting tactics. Three of the four studied specimens featured severe bite damage focused explicitly on the facial region—the snout, forehead, or lower jaw. This distinct pattern closely mirrors actualistic taphonomy experiments and observations of living saltwater crocodiles and Nile crocodiles. Modern crocodiles are ambush predators that strike thirsty land animals at the water’s edge, instinctively grabbing their prey by the head or snout before dragging them into deep water to drown them.
The presence of a deeply curved “hook score” on the jawbone of the juvenile Granastrapotherium provides further violent details. Such curved gouges are produced when a crocodile violently shakes, thrashes, or performs a “death roll” to dismember heavy prey.
“We propose that the trace fossils identified here, likely produced by Purussaurus, suggest that it hunted and processed food in a similar way to the largest modern crocodiles,” the authors explain. “These crocodiles therefore may be used as reasonable ecological analogues of Purussaurus, though we appreciate that nuances of the ecology of prey and predators in the Miocene may have been different.”
The study also uncovers evidence of complex, multi-stage feeding behaviors involving secondary scavengers. On the outer surface of the Xenastrapotherium jawbone, alongside the deep, crushing punctures left by a massive Purussaurus, the team identified an entirely different trace fossil: Knethichnus parallelum. This trace consists of a series of ten fine, strictly parallel linear grooves caused by a serrated tooth slipping across the bone.
Because Purussaurus possessed smooth, conical teeth, these parallel scratches were made by a different creature altogether. The authors attribute these fine scratches to Langstonia huilensis, an extinct sebecid crocodyliform. Unlike aquatic caimans, Langstonia was a fully terrestrial, deep-snouted predator equipped with blade-like, ziphodont (serrated) teeth. Reconstructing the maximum prey size for the smaller, land-dwelling Langstonia indicates that an adult Xenastrapotherium was far too large for it to hunt actively. Instead, the overlapping bite marks reveal a dramatic ancient scene: after a massive Purussaurus killed the giant mammal and fed, the terrestrial Langstonia moved in as a opportunistic scavenger to pick at the remaining carcass.
The significance of this discovery extends far beyond simply documenting an ancient reptile eating a prehistoric mammal. It fundamentally transforms our understanding of Neotropical food webs during the Miocene. In modern ecosystems, large warm-blooded mammalian carnivores regulate herbivore populations and drive the flow of nutrients. In Miocene Colombia, cold-blooded reptiles were the true ecosystem engineers.
Because giant ectotherms like Purussaurus consumed massive terrestrial herbivores and dismembered them at the water’s edge, they acted as vital conduits for nutrient transfer, shifting massive amounts of biological energy from land into freshwater river systems through messy feeding and defecation. By leaving partially consumed megaherbivores scattered along riverbanks, these giant apex predators created rich scavenging opportunities that supported an array of secondary consumers, including terrestrial sebecids, turtles, terror birds, and freshwater fish.
Ultimately, this physical evidence confirms that giant crocodylians were not just passive river-dwellers, but the undisputed top predators of South America’s Miocene megafauna, shaping the evolutionary dynamics of an ancient, lost world.
Endnotes
EurekAlert! / Society of Vertebrate Paleontology Press Release (2026). Physical evidence of crocodylian predation on ungulates in the Middle Miocene of Colombia. https://www.eurekalert.org/news-releases/1140123
Wilson, O. E., Moreno-Bernal, J. W., Suarez, C., Cardozo Tovar, F., Vanegas, A., Vanegas, R., Shirley, E. A., Holroyd, P. A., & Zonneveld, J.-P. (2026). Physical evidence of crocodylian predation on ungulates in the Middle Miocene of Colombia. Journal of Vertebrate Paleontology. https://doi.org/10.1080/02724634.2026.2701154
IMAGE CREDIT: Miguel Hernandez.