Giant caimans may have been South America’s top predators 13 million years ago
Around 13 million years ago, the north of South America was a world of giants. Massive herbivores, ‘terrible birds’ and sabre-toothed predators roamed the shores of vast bodies of water, whilst enormous relatives of modern caimans lurked beneath the surface. New research into fossilised bones has shown that it was crocodilians that may have been among the most important predators in this ecosystem. The clue came from tooth marks preserved on the bones of large mammals.
Palaeontologists have studied fossils dating back approximately 10.5–16 million years, which were found in Colombia and are now held in museum collections.
They paid particular attention to damage to the bones of ancient ungulates — bite marks and tooth marks left by predators.
Such marks are particularly valuable to palaeontologists. Finding the remains of two species close together does not in itself mean that one hunted the other. However, tooth marks on a bone provide direct evidence that a predatory interaction did indeed take place between the animals.
Analysis has shown that a significant proportion of the damage corresponds to the bites of large crocodilians.
Details
One of the most impressive inhabitants of these ecosystems was Purussaurus neivensis — a large relative of modern caimans.
According to the estimates used by the study’s authors, individual specimens could have reached around 7 metres in length and weighed approximately 1.8 tonnes. However, the reconstruction of the sizes of extinct animals depends on the methodology used, so such figures should be regarded as approximate.
Purussaurus had a massive head and powerful jaws capable of handling very large prey.
The frequency of footprints that researchers associate with this predator suggests that it may have occupied an exceptionally important place in the food web.
Miocene South America was very different from the continent we know today.
The shores of its water bodies were home to giant ground sloths, glyptodonts — armoured relatives of armadillos — as well as unusual ungulates such as astrapotheres and toxodonts. Some of them weighed more than a tonne.
There was no shortage of predators either. The region was home to enormous snakes, sabre-toothed mammals, flightless predatory ‘terrible birds’ and sebecids – terrestrial relatives of crocodiles.
However, researchers believe that mammalian predators alone were not sufficient to utilise the full available biomass of large prey. Crocodilians may have occupied a significant part of this ecological niche.
There is an important caveat here.
Damage to the bone indicates that a crocodile interacted with the animal’s carcass, but does not always allow us to determine whether it killed the animal itself.
The predator may have attacked live prey, or it may have fed on an animal that had already died. It is therefore more accurate to say that giant caimans actively utilised large mammals as a food source, rather than to claim that every trace found is evidence of a successful hunt.
Nevertheless, the high frequency of such marks allows the authors to suggest that crocodilians played a significant role amongst the ecosystem’s large predators.
If giant caimans regularly hunted large animals, their impact could have extended far beyond individual attacks.
In modern ecosystems, large predators are capable of influencing prey numbers, their behaviour and even the structure of entire communities.
The authors suggest that Purussaurus and other crocodilians may have played a similar role in tropical South America millions of years ago.
However, the study primarily concerns the specific fossil fauna of the Middle Miocene in Colombia. It would therefore be premature to generalise the findings to the entire South American continent without further data.
Why this is important
Ancient food webs are usually reconstructed indirectly — based on the sizes of animals, the structure of their teeth, and which species coexisted.
Bite marks allow us to take the next step and observe the actual interactions between predator and prey.
The new study shows that crocodilians in the Miocene ecosystems of northern South America were not merely large inhabitants of water bodies. They may have occupied one of the key predatory niches and competed for large prey with the most dangerous terrestrial predators of their time.
Source
Study:
Physical evidence of crocodylian predation on ungulates in the Middle Miocene of Colombia.
Journal: Journal of Vertebrate Palaeontology, 2026.