Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news about fascinating discoveries, scientific advances and more
A rare fossil has provided a snapshot of an extremely unlucky day for a prehistoric sea cow.
A now-extinct species of dugong, a sea cow-like marine mammal, was swimming in the sea about 15 million years ago when it was preyed upon by two animals: a crocodile and a tiger shark. The latter sunk one of its teeth into the sea cow’s body.
As a result of the analysis of a fossil found in Venezuela, researchers were able to reveal how the sea cow, which belongs to an extinct animal group called Culebratherium, became extinct.
The research, published Thursday in the Journal of Vertebrate Paleontology, captures a moment in time that provides a unique glimpse into how the food chain functioned during the early and middle Miocene Epoch, 11.6 million to 23 million years ago.
“It’s very rare to find evidence of two predators in a single specimen,” says lead study author Aldo Benites-Palomino, a doctoral student in the department of paleontology at the University of Zurich, Switzerland. “This shows why we need to look for fossils in tropical areas like (Venezuela).”
Anatomy of an attack
The fossilized remains — a partial skull and 13 vertebrae, or backbones — revealed three types of bite marks, the shape, depth and orientation of which suggested they were made by two predators: a small- to medium-sized crocodile and a tiger shark.
The crocodile-like creature attacked first, striking the dugong’s snout with deep teeth, suggesting that the dugong was trying to grab that part of its face and strangle it, according to the study. Two other large, curved cuts suggest that the crocodile was dragging the dugong and tearing at its flesh.
The lines and cuts on the fossil suggest the crocodile performed a “death somersault” to disarm its prey, a spinning behavior also observed in living crocodile species.
“Such marks only occur as a result of incidents in which biting is followed by tearing, rolling or grasping,” the study authors wrote.
The sea cow was then torn apart by a tiger shark, which has narrow, unserrated teeth. It can be difficult to distinguish between signs of active hunting and scavenging, but the bite marks on the sea cow’s body, and the irregular distribution and variation in depth, suggested to the researchers that this was the behavior of a scavenger, such as a tiger shark, according to the study.
Scientists confirmed the shark’s identity with the discovery of an isolated tooth belonging to Galeocerdo aduncus, an extinct species of tiger shark, in the neck of a sea cow.
“I had to work like a forensic scientist,” Benites-Palomino recalls.
However, the study noted that considering the fragmented structure of the skeleton, other scenarios for the death of the sea cow cannot be ruled out.
Dean Lomax, a paleontologist at the Universities of Bristol and Manchester in England who was not involved in the research, said he agreed with the study’s findings but said it was difficult to distinguish between scavenging behavior and active hunting behavior.
“For example, it’s perhaps not unreasonable to think that the dugong may have been long dead, perhaps floating and bloating up, then being eaten by crocodiles and sharks at different times,” Lomax, author of “Locked in Time: Animal Behavior in 50 Surprising Fossils,” says via email.
“Unless we have direct evidence that the dugong was inside the crocodile (as a final meal), or that the crocodile and dugong died during the attack, it’s always rare to say 100% that this was the result of an active scavenging attack,” Lomax added.
Accidental fossil discovery
At the time, sea cows may have been 5 meters (about 16 feet) long, and their fatty tissues may have been a good source of food, Benites-Palomino said.
Today, crocodiles, killer whales and sharks prey on dugongs and sea cows, mostly targeting the young, as adults are difficult to kill due to their size. It’s not clear exactly which species of crocodile preyed on the sea cow — it could have been an extinct species of caiman or gavial known for its long, thin snout, but it would have been large — between 4 and 6 meters (about 13 to 20 feet) long.
“There are several candidates. South America was a paradise for crocodiles at the time,” Benites-Palomino added.
A farmer south of the Venezuelan city of Coro has discovered the remains of a sea cow for the first time in a place where fossils had never been found before.
“Initially, we were unfamiliar with the geology of the site, and the first fossils we uncovered were fragments of skulls. It took us a while to determine what they were – sea cow skulls, which are quite peculiar in appearance,” said Marcelo Sánchez-Villagra, director of the Institute and Museum of Paleontology at the University of Zurich and one of the study’s co-authors.
Benites-Palomino said the rare discovery demonstrates the value of fossil hunting in “non-classical” South America.
“We’ve been going to the same fossil sites in North America and China for a long time, but every time we work in these new areas we’re constantly finding new fossils.”
For more CNN news and bulletins, create an account at CNN.com