In 2019, a team of palaeontologists found the remains of an animal in the outcrops of the Agua Clara Formation, south of the city of Coro in north-west Venezuela. The fragmented skeleton included a partial skull and 18 vertebrae.
The animal was identified as an ancient dugongine sea cow – similar to the modern-day manatee – belonging to the extinct genus Culebratherium.
What was more astonishing, however, was the predator marks that the scientists identified on the skeleton, which suggest that it was first attacked by an ancient crocodile and then scavenged by tiger sharks.
The findings, published in the Journal of Vertebrate Paleontology, shed new light on prehistoric food chains – in particular the predatory behaviour of ancient creatures during the Early to Middle Miocene epoch, 23 million to 11.6 million years ago.
A gruesome yet profound discovery
The scientist found "conspicuous" deep tooth impacts concentrated on the sea cow's snout, suggesting the crocodile first tried to grasp its prey around its nose and mouth in an attempt to suffocate it.
The team located two further large incisions, deducing that the crocodile dragged the sea cow through the water before tearing at its flesh. Slash marks detected on the fossils indicate the crocodile then performed a 'death roll', a behaviour commonly used by modern crocodiles.
The tooth of a tiger shark was found in the sea cow's neck, along with shark bite marks all over the skeleton, suggesting the remains of the animal were preyed upon by scavengers.
Despite the gruesome nature of the sea cow's death, the researchers say the findings are significant because they provided rare evidence of the way ancient food chains functioned.
While evidence of food chain interactions is not scarce in the fossil record, it is often ambiguous, explains lead-author Aldo Benites-Palomino, from the Department of Paleontology at Zurich. This makes differentiating between marks of active predation and scavenging events challenging.
"Today, often when we observe a predator in the wild, we find the carcass of prey which demonstrates its function as a food source for other animals too; but fossil records of this are rarer," says Benites-Palomino.
"We have been unsure as to which animals would serve this purpose as a food source for multiple predators. Our previous research has identified sperm whales scavenged by several shark species, and this new research highlights the importance of sea cows within the food chain.
"Our findings constitute one of the few records documenting multiple predators over a single prey, and as such provide a glimpse of food chain networks in this region during the Miocene."
The dig
The team say the sea cow fossil is "remarkable", not only for what it tells us about marine food chains millions of years ago, but also because of where it was found, 100 kilometres away from previous fossil finds.
"We first learned about the site through word of mouth from a local farmer who had noticed some unusual "rocks." Intrigued, we decided to investigate," says co-author Marcelo R Sanchez-Villagra, who is the Director at the Palaeontological Institute & Museum at Zurich.
"Initially, we were unfamiliar with the site's geology," explains Sanchez-Villagra, "and the first fossils we unearthed were parts of skulls. It took us some time to determine what they were -- sea cow remains, which are quite peculiar in appearance.
"By consulting geological maps and examining the sediments at the new locality, we were able to determine the age of the rocks in which the fossils were found.
"Excavating the partial skeleton required several visits to the site. We managed to unearth much of the vertebral column, and since these are relatively large animals, we had to remove a significant amount of sediment.
"The region is known for evidence of predation on aquatic mammals, and one factor that enabled us to observe such evidence was the excellent preservation of the fossil's cortical layer, which is attributed to the fine sediments in which it was embedded.
"After locating the fossil site, our team organized a paleontological rescue operation, employing extraction techniques with full casing protection.
"The operation took 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 cranial elements."
Read more about the study: Trophic interactions of sharks and crocodylians with a sea cow (Sirenia) from the Miocene of Venezuela. 2024. Aldo Benites-Palomino, Gabriel Aguirre-Fernández, Jorge Velez-Juarbe, Jorge D. Carrillo-Briceño, Rodolfo Sánchez, Marcelo R. Sánchez-Villagra. Published with license by the Society of Vertebrate Paleontology.
Main image: Artist's impression of ancient crocodile and sharks attacking the sea cow. Credit: Jaime Bran Sarmiento
More wild stories from around the world
- Extinct-in-the-Wild sihek birds begins journey back to Pacific home
- Child finds mammoth tooth in playground on Vancouver Island – and it has got scientists very excited
- Golden bats and giant snakes are hiding deep inside in Mexico's ancient temples – and scientists know why
- "We found 20 pairs of wings in an hour.” Culprit of Jamaica's dismembered bats caught on camera
