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Ancient caiman may have preyed on another apex predator—the giant 'terror bird'

The La Venta fossil site in Colombia is home to a rich fossil record, yielding a particularly diverse set of vertebrate fossil assemblages. The giant terror bird (phorusrhacid) and caiman—a large crocodile-like reptile—were known to be two of the apex predators roaming this region during the middle Miocene epoch. Although the terror bird was a terrestrial predator and the caiman was an aquatic predator, new evidence shows that they occasionally crossed paths, and that these meetings did not go well for the terror bird.

A new study, in Biology Letters, details the analysis of a terror bird's leg bone, which was found to have a set of tooth marks that resulted in the bird's death. Until this finding, there had been little evidence that these predators ever interacted with each other. However, the study authors note that terrestrial and aquatic predators may have met at certain times.

"Terrestrial apex predators may preferentially wander close to water sources—especially in dry seasons—as these areas may set an ideal scenario for terrestrial predators to feed on aquatic taxa, or to attempt to prey on other taxa obliged to drink water from water sources. Thus, aquatic predators can prey on terrestrial vertebrates—including apex predators—as they approach water sources, similar to what is known from aquatic water holes in Africa," the researchers write.

The fossilized bone of the terror bird was found with four distinct tooth marks. The researchers analyzed the marks using 3D surface scanning and digital modeling and found them to most closely match a caiman species called Purussaurus neivensis, a species which was native to the La Venta area around the same time the terror bird existed.

The tooth marks showed no signs of healing, meaning the terror bird died around the time of the encounter. However, the researchers note that it's possible that the bite could have occurred after the death of the bird, as a scavenging event rather than direct predation. Either way, it was clear that the terror bird did not go on to live after the encounter.

The frequency of apex predator encounters like this remains unknown, and there is still some uncertainty around whether the reptile was a Purussaurus neivensis or another similar species. Still, this finding provides a rare glimpse into the complex world of prehistoric ecosystems and predator-prey dynamics, showing that even giant terror birds might be subject to attacks from other predators.