Deep punctures, crushed bones, and cracks that spread around the impact site are allowing researchers to reconstruct violent encounters that occurred more than 10 million years ago. A new study of fossils from the La Venta region of Colombia presents physical evidence that giant crocodiles attacked—or at least ate—some of the large mammals that lived in South America at the time.
The study, published in the journal Journal of Vertebrate Paleontology, focuses on four fossils of herbivorous mammals from three species. Markings were found on the bones that corresponded in size and shape to the teeth of Purussaurus neivensis, an ancient relative of modern caimans, estimated to be about seven meters long and weigh about 1,800 kilograms.
According to Dr. Oscar Wilson of the University of Helsinki, who led the study, the prevalence of symptoms attributed toPorosaurus Indicates thatתנינאים Played a particularly important role in tropical ecosystems of South America During the period ofMiocene, and especially in the predation of large animals.
Four bones and three mammal species
The fossils examined date back to between 16 and 10.5 million years ago. They belong to large mammals that lived in the area. La Venta, now part of the Tatacoa Desert inColombia.
One of them was Pericotoxodon platignathus, a mammal from the toxodont group that was similar in size to a rhinoceros. The other two species, Xenastrapotherium kraglievichi and-Granastrapotherium snorki, belonged to the astropotherium – an extinct group of large South American mammals, some of which resembled hippos or small elephants in their body structure.
The weight of the animals tested is estimated at 600 to 1,800 kilograms. In other words, the crocodile was not content with fish, turtles, or small animals that came close to the water, but was also capable of dealing with some of the largest herbivores in its environment.
The researchers identified round holes, deep depressions, grooves and fractures in the fossils that formed when the bone was still fresh. One fossil had a hole nearly three centimeters in diameter. Another bone bore five holes with cracks spreading around them – a pattern indicating that a great deal of force was exerted on a bone that had not had time to dry or petrify.
Who left the bite marks?
Identifying a predator based on a bite mark alone is not simple. The teeth of different animals may leave similar marks, and bones may also be damaged after death by geological pressure or weathering processes.
Therefore, the researchers compared the size and shape of the holes to 22 isolated teeth of Purussaurus neivensisThe match between the teeth and the impact marks, along with the intensity of the crushing and the location of some of the marks in the head and jaw area, supported the identification of Porosaurus as the most likely cause.
Porosaurus was not a crocodile in the strict taxonomic sense, but a caiman. However, its lifestyle was probably similar to that of large contemporary crocodiles: ambushing from the water, a short charge, and a powerful bite designed to capture prey and drag it into the water.
Three of the four fossils examined bore marks on the head or jaw area. Modern crocodiles also often attack the head of a mammal approaching to drink, so this pattern strengthens the possibility that this was a hunting attempt and not just a carrion feeding.
Predator or scavenger?
Despite the headlines, a bite fossil is not a video camera from the Miocene. A bite mark can be formed during hunting, but also when a predator eats an animal that has already died for some other reason.
The lack of signs of healing suggests that the injuries occurred very close to the animals' death, but does not by itself prove that the bite killed them. The fractures in fresh bones, the location of the marks, and the consistency with the behavior of modern crocodiles support a predation interpretation in at least some cases, but the researchers do not rule out scavenging.
One of the jaws even appears to record two separate events. Alongside the large perforations attributed to Porosaurus, small parallel marks and scratches were found, which may correspond toLangstonia huilensis – A terrestrial saber-toothed lizard estimated to be about 4.2 meters long. Saber-toothed lizards were extinct relatives of crocodiles, but unlike modern crocodiles, they hunted on land.
The possibility that two Predators Different individuals ate from the same individual illustrates the difficulty in distinguishing between hunting and scavenging. It is possible that the Porosaurus killed the mammal and the scavenger came to the carcass later, but other scenarios are also possible.
A world where crocodiles replaced apex predators
Miocene South America was very different from the continent we know today. It was isolated from North America, and many of the animals that lived there evolved independently over millions of years.
The La Venta region was part of a vast system of rivers, lakes, swamps, and tropical forests. Along with the large mammals, it was home to giant turtles, large snakes, flightless birds of prey known as "terror birds," predatory metatherians with sword-like fangs, and several groups of marine and terrestrial crocodiles.
The abundance of herbivores allowed for a diverse community of predators. However, according to the researchers, carnivorous mammals alone did not exploit all the available food sources. Crocodiles – led by Porosaurus – filled part of the niche now occupied by lions, tigers and large crocodiles.
Bite marks provide rare direct evidence of these interactions. Most fossils tell us which animals lived in a particular place, but they don't necessarily tell us who ate whom. A tooth left embedded in bone, a hole corresponding to a particular tooth, or a fragment created during a bite can turn a species list into a picture of an active food web.
Did crocodiles really "dominate" the food chain?
The four fossils strongly support the hypothesis that large crocodiles preyed on large mammals and were an important component of the La Venta predator community. However, this is a small sample, not collected as part of a systematic survey of all the bones at the site.
Therefore, the findings do not allow us to calculate how often the attacks occurred or to determine with certainty that Porosaurus was responsible for more predation than any other predator group. The statement that crocodiles "dominated" theFood chain It is a reasonable ecological conclusion based on their size, frequency, and new evidence – but not a direct count of all predation incidents.
The importance of the study lies in presenting physical evidence that crocodiles were not just background inhabitants of Miocene waterways. They attacked or ate animals weighing more than a ton, and therefore could have influenced the behavior, distribution, and perhaps even the population size of large herbivores.
Questions and Answers
**What was it? Purussaurus neivensis?** A giant crocodile, a relative of modern caimans, that lived in northern South America during the Miocene epoch. It was estimated to be about seven meters long and weigh about 1.8 tons.
How do we know it bit the mammals? The researchers compared the size and shape of the bite marks to fossilized teeth of Porosaurus. The perforations, crushing, and fractures in the fresh bone were consistent with the teeth and size of the crocodile.
Do the bite marks prove that the Porosaurus hunted animals? Not in all cases. The marks prove contact of the teeth with the bones near death, but some may also have been formed while eating a carcass. The location of the injuries and the pattern of the fractures support predation in some cases.
Why is the research important? Because it provides direct evidence of predator-prey relationships in an ancient ecosystem, and shows that giant crocodiles were capable of attacking mammals weighing hundreds of kilograms and even more than a ton.
Sources
- The article in the Journal of Vertebrate Paleontology
- University of Helsinki announcement on the EurekAlert website
- Report and photos of the fossils on the Phys.org website
More on the subject on the science website
- The largest crocodile that ever lived could swallow a man
- Prehistoric crocodile fossils in Brazil
- Tyrannosaurus tooth found stuck in dinosaur skull reveals attack
- T-Rex was a hunter and not just a scavenger
- The rise to greatness of the mammals
For the scientific article: Opening the scientific article
