Fossil traces of a fate millions of years ago: A prehistoric manatee was once killed by a crocodile in a death roll and then served as food for a shark, according to a find from Venezuela. It is a rare example of traces of two different carnivores on one fossil. The discovery also sheds light on hunting strategies and the food chain in the Caribbean region during the Miocene, say the researchers.
Who hunted whom in former ecosystems and who acted as a scavenger? Bite marks on fossil remains sometimes provide clues to these so-called trophic interactions between animals of the past. The current case focuses on a habitat that was once located in what is now northern Venezuela. In the Miocene era, a shallow extension of the Proto-Caribbean stretched there. In the shallow coastal waters of this marine region, extinct representatives of the manatees were also active – and apparently served as food for predators, as demonstrated by the discovery that researchers led by Aldo Benites-Palomino from the University of Zurich are now reporting on.
The fossil was discovered in a layer of the so-called Agua Clara Formation near Coro in Venezuela, which dates back to the early to middle Miocene – about 23 to 11.6 million years ago. “We learned about the site from a local farmer who noticed some unusual rocks,” says senior author Sanchez-Villagra from the University of Zurich. During their investigations, the team was surprised to discover that they were manatee fossils.
Manatee fossil with tooth marks
The excavation ultimately uncovered a partial skeleton of the prehistoric manatee: pieces of the skull, eighteen vertebrae and rib fragments. Based on these characteristics, the researchers were able to classify the animal as belonging to the genus Culebratherium. However, as the more detailed examination of the fossil remains showed, the find is more than just fossil evidence of a prehistoric manatee: the team found bite marks on the bones in various places.
Some were dot-shaped, suggesting that they came from a prehistoric crocodile that was apparently hunting for prey in shallow sea water.
Special tooth marks were found on the so-called rostrum – the bony base of the manatee’s snout: they bear the characteristics of pulling or twisting force. According to the researchers, this reflects the fact that the crocodile probably tried to suffocate the manatee by grabbing it by the nose. Certain tooth marks also suggest that the predator performed a so-called death roll. Even today’s crocodiles still use this technique to increase the damage after biting into their prey by twisting. Tooth marks on other bones also make it clear that the crocodile was successful and eventually consumed parts of the manatee.
A feast for two
However, the victim apparently did not become a complete crocodile feast: The team discovered tooth marks in various places on the fossil that did not come from the reptile, but from a shark. This was finally confirmed by the discovery of a tooth in the area of the manatee’s neck, which the researchers were able to attribute to a tiger shark (Galeocerdo aduncus). According to them, the findings thus show that the manatee was once captured and eaten by a prehistoric crocodile, and later a tiger shark devoted itself to the rest of the prey as a scavenger.
“Today we often observe that carcasses captured by predators are eaten by other animals – but fossil evidence of this behavior is rare,” emphasizes Benites-Palomino. “In addition, this new discovery shows the importance of manatees in the prehistoric food chain of the region. Our results thus offer a rare insight into the complex predator-prey relationships of the Miocene, about 23 to 11.6 million years ago,” says the paleontologist.
Source: Taylor & Francis Group, specialist article: Journal of Vertebrate Paleontology, doi: 10.1080/02724634.2024.2381505