More than 10 million years ago, South America was home to a remarkable Miocene ecosystem filled with giant animals and powerful predators. Vast lakes covered much of the continent, providing habitat for enormous turtles and crocodiles, while extraordinary hunters stalked the surrounding shores.
Among these predators were anacondas, saber-toothed mammals, flightless “terror birds,” and sebecids—land-dwelling relatives of modern crocodiles. New research suggests that crocodilians played a particularly important role in this ancient ecosystem, making them one of the region’s most influential predator groups.
“There was so much prey that the mammalian predators couldn’t eat it all,” said Oscar Wilson, a postdoctoral researcher at the University of Helsinki.
“Our new study shows that crocodiles were the most important predators in this region, especially when hunting large prey.”
A lost Miocene ecosystem filled with giant prey
The shores of these ancient lakes supported a remarkable variety of herbivores. Giant ground sloths lived alongside glyptodonts—the heavily armored relatives of modern armadillos—and several groups of ungulates. Although ungulates are hoofed mammals, many extinct South American species looked very different from familiar animals such as horses and deer.
These animals included astrapotheres, sometimes called “thunder beasts,” and toxodonts. Some of these ancient mammals reached enormous sizes and weighed more than a ton.
The abundance of large herbivores helped support predators that were equally impressive in size.
The giant crocodile at the top of the food chain
The largest known predator in this ecosystem was Purussaurus neivensis, a giant crocodilian related to modern caimans. It grew to approximately 7 meters long and weighed about 1,800 kilograms.
Its enormous size placed Purussaurus near the top of the food chain. The giant crocodilian may also have influenced more than individual hunting events. Researchers suggest that it could have helped shape herbivore populations across the entire ecosystem.
This possibility offers scientists a glimpse into how powerful crocodilians helped shape ancient tropical communities rather than simply coexisting with other large predators.
Fossil bite marks reveal ancient crocodile predation
To determine which animals actually attacked their prey, researchers examined fossils preserved in museum collections. The evidence came from bite marks and tooth impressions found on the fossilized remains of herbivores.
These marks are especially valuable because they provide direct evidence of interactions between predators and prey. Instead of relying only on an extinct animal’s size, anatomy, or presumed hunting ability, researchers can study the marks left on bones to identify signs of feeding and aggression.
The fossils analyzed in the study were between 10.5 million and 16 million years old.
“The frequency of marks probably made by Purussaurus suggests that these giant crocodilians were important predators in these ancient tropical ecosystems,” Wilson said.
The research was published in the Journal of Vertebrate Paleontology.
Source: www.sciencedaily.com