Giant crocodylians dominated the food chain in Miocene South America, fossil evidence suggests

Fossil evidence indicates that giant crocodylians ruled the food chain in Miocene South America, according to a new study. Researchers analyzed bite marks on ancient herbivore bones to determine which animals were the primary predators in the region. These findings suggest that massive crocodile-like creatures, rather than mammals such as saber-toothed cats or terror birds, were the dominant hunters in the area around 10 to 16 million years ago. The study focuses on a vast inland lake that once covered much of South America, teeming with life. This ecosystem included enormous herbivores like giant ground sloths, glyptodonts, armored mammals related to modern armadillos, and various groups of ungulates, including astrapotheres and toxodontids. Some of these herbivores weighed more than a tonne, making them challenging prey for even the largest terrestrial carnivores. Among the predators that thrived in this environment were anacondas, saber-toothed mammals, flightless "terror birds," and sebecids, ancestors of today’s crocodiles. However, the research reveals that crocodylians, particularly a species known as Purussaurus neivensis, played the most crucial role in shaping the food web. This creature, which could grow up to seven meters long and weigh nearly two tonnes, was one of the largest land-based predators of its time. The researchers used physical evidence found on fossilized bones to support their conclusions. They examined bite marks and tooth impressions left on herbivore remains, identifying patterns consistent with crocodylian predation. These marks were frequently observed on bones attributed to large ungulates, suggesting that Purussaurus was a regular hunter in the region. The study notes that the presence of such frequent predatory activity implies that these crocodylians had a significant impact on the population sizes of their prey. The research team, led by Oscar Wilson, a postdoctoral researcher at the University of Helsinki, emphasizes that the abundance of prey allowed crocodylians to dominate the ecosystem. Mammalian predators, despite their size and strength, could not consume all the available food, leaving room for crocodylians to thrive. According to Wilson, the data supports the idea that these ancient reptiles were among the most influential predators in the Miocene landscape. The study draws upon a collection of fossils housed in museums, many of which date back between 10.5 million and 16 million years. These specimens provide critical insights into the ecological dynamics of the period. The research highlights how the interactions between predators and prey can be reconstructed through forensic examination of fossil records. In some cases, the same bones show signs of multiple types of interaction, including both predation and scavenging by different species. The implications of the study extend beyond understanding past ecosystems. It offers a glimpse into the complex relationships that shaped prehistoric environments and underscores the adaptability of crocodylians as apex predators. The work contributes to broader discussions about the evolution of predator-prey dynamics and the factors that influence the dominance of certain species in ecological systems.