Ancient manatee attacked by both an ancient crocodile and a shark sheds new light on prehistoric food chains

A new study shows how a prehistoric manatee was hunted by not one but two different carnivores – a crocodile and a shark – shedding light on the hunting tactics of ancient creatures as well as the broader food chain millions of years ago.

Published in Journal of Vertebrate PalaeontologyThe finds represent one of the only examples of a creature being attacked by two different predators in the early to middle Miocene (23 to 11.6 million years ago).

It is believed that the dugongin sea cow, which belongs to the extinct genus Culebratherium, was first attacked by the protocrocodile and then eaten by a tiger shark (Galeocerdo aduncus) in what is now northwestern Venezuela.

“Conspicuous” deep tooth marks concentrated on the manatee’s snout suggest that the crocodile initially attempted to grab its prey by the snout in order to suffocate it.

Two other large cuts with a rounded initial blow show that the crocodile then dragged the manatee along and subsequently tore it apart. Grooves and cut marks on the fossils indicate that the crocodile probably performed a “death roll” when grabbing its prey – a behavior commonly seen in modern crocodiles.

A tiger shark (Galeocerdo aduncus) tooth found near the manatee's neck, as well as shark bite marks visible throughout the skeleton, show how the animal's remains were subsequently dismembered by this scavenger.

The team of experts from the University of Zurich, the Natural History Museum of Los Angeles County and the Venezuelan institutes Museo Paleontológico de Urumaco and Universidad Nacional Experimental Francisco de Miranda explain that their findings add to the evidence that the food chain behaved similarly millions of years ago as it does today.

“Today, when we observe a predator in the wild, we often find the carcass of the prey, which proves its function as a source of food for other animals; however, fossil finds are rarer.

“We were previously unsure which animals would have served this purpose as a food source for multiple predators. Our previous research has shown that sperm whales are eaten by several shark species, and this new research underscores the importance of manatees within the food chain,” explains lead author Aldo Benites-Palomino of the Department of Paleontology in Zurich.

“Although evidence of food chain interactions is not rare in the fossil record, it is usually represented by fragmentary fossils that contain traces of ambiguous significance. Distinguishing between traces of active predation and scavengers is therefore often challenging.

“Our results are one of the few pieces of evidence that multiple predators attacked the same prey and as such provide insight into food chains in this region during the Miocene.”

The team's discovery was made in outcrops of the early to middle Miocene Agua Clara Formation south of the city of Coro, Venezuela.

Among the remains they found a fragmentary skeleton that included a partial skull and eighteen associated vertebrae.

Co-author and professor of paleobiology Marcelo R. Sanchez-Villagra described the excavation as “remarkable” – especially because of the site, which is 100 kilometers away from previous fossil finds.

“We first heard about this site through word of mouth from a local farmer who had noticed some unusual stones. We were intrigued and decided to get to the bottom of it,” says Sanchez-Villagra, director of the Paleontological Institute and Museum in Zurich.

“Initially, we were unfamiliar with the geology of the site and the first fossils we dug up were skull fragments. It took us a while to figure out what they were – manatee skulls, which have a rather peculiar appearance.

“By consulting geological maps and studying the sediments at the new site, we were able to determine the age of the rocks in which the fossils were found. Excavation of the partial skeleton required several site visits. We managed to expose much of the spine and, since these are relatively large animals, we had to remove a significant amount of sediment.

“The region is known for its evidence of predators, and one factor that enabled us to observe such evidence was the excellent preservation of the fossil's cortical layer, due to the fine sediments in which it was embedded.

“After finding the fossil deposit, our team organized a paleontological rescue operation, using extraction techniques with complete protection of the shell. The operation lasted about seven hours, with a team of five people working on the fossil. The subsequent preparation took several months, especially the meticulous work of preparing and restoring the skull elements.”