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A rare fossil has provided a snapshot of what must have been an exceptionally unlucky day for a prehistoric sea cow.
A now-extinct species of dugong, a manatee-like marine mammal that swam in the ocean 15 million years ago, was preyed upon by two animals: a crocodile and a tiger shark. The latter stuck one of its teeth into the sea cow’s body.
By analyzing a fossil found in Venezuela, researchers were able to piece together how the sea cow, a member of an extinct group of animals known as the Culepratherium, became extinct.
their studyPublished Thursday in the Journal of Vertebrate Paleontology, it provides unique insight into how the food chain worked during the middle Miocene epoch, 11.6 million to 23 million years ago.
“It is very rare to find evidence of two predators in the same specimen,” said lead study author Aldo Benitz-Palomino, a doctoral student in paleontology at the University of Zurich in Switzerland. “This shows why we need to study fossils in tropical areas like (Venezuela).”
The fossilized remains — a partial skull and 13 vertebrae, or vertebrae — revealed three types of bite marks. Their shape, depth, and orientation suggested they were made by two predators: a small to medium-sized crocodile and a tiger shark.
The crocodile-like creature struck first and, according to the study, had a deep tooth impact on the sea cow’s nose, suggesting it tried to suffocate this part of the dugong’s face. Two other large, curved scratches indicate that the crocodile dragged the sea cow and tore into its flesh.
The fights and slashing over the fossil enabled the alligator to execute the “death roll,” a spinning behavior to subdue prey that is also seen in living alligator species.
“This type of mark is produced only by biting events in which successive tearing, rolling, or grasping actions are executed,” the study authors noted.
Later, the sea cow is a tiger shark with narrow, blunt teeth. Distinguishing between active hunting and scavenging is challenging, but according to the study, the irregular distribution and depth variation of bites across the sea cow’s body suggest to researchers that it is the behavior of a tiger-like scavenger. Shark.
Scientists have confirmed the shark’s identity by finding an isolated tooth in the neck of a sea cow belonging to the extinct tiger shark Galeocerdo aduncus.
“I had to work as a forensic scientist,” recalls Benítez-Palomino.
However, given the fragmentary nature of the skeleton – other scenarios for the sea cow’s extinction cannot be ruled out, the study noted.
Dean Lomax, a paleontologist at the University of Bristol and the University of Manchester in England, said he agreed with the study’s findings, but said it was difficult to distinguish between scavenging and active predatory behavior.
“For example, it’s not unreasonable to think that the dugong was already dead, perhaps floating and bloated, and then feasted on crocodile and shark(s) at different times,” Lomax said. , author “Locked in Time: Animal Behavior Discovered in 50 Amazing Fossils,” via email.
“Unless we have direct evidence that the dugong inside the egg (as a last meal) or the croc and dugong died in the time between the attack, it is inherently difficult to say 100% whether this was the result of a serious attack. Cleanup,” Lomax added.
Sea cows were probably 5 meters (about 16 feet) long at the time, Benítez-Palomino said, and their fat tissue would have been a good food source.
Today, crocodiles, orcas, and sharks prey on dugongs and manatees, often targeting the young because their size makes it difficult to kill the adults. It’s not known exactly what kind of crocodile would have preyed on the sea cow – it could have been an extinct caiman or gharial, known for its long, thin snout, but it would have been huge – 4 to 6 meters (about 13 to 20 feet) long.
“There are many candidates. South America was a paradise for crocodiles back then,” Benítez-Palomino added.
A farmer south of Coro, Venezuela, first noticed the sea cow in a place where no fossils had been found before.
“Initially, we didn’t know the geology of the site, and the first fossils we found were parts of skulls. It took us a while to determine what they were – sea cow skulls, which are very different in appearance,” said study co-author and professor of paleontology at the university’s Institute of Paleontology. and Marcelo Sánchez-Villagra, director of the museum, said in a statement.
Benites-Palomino said the rare find shows the value of fossil hunting in “non-classical” South America.
“We’ve been visiting the same fossil sites in North America and China for a long time, but we’re constantly finding new fossils every time we work in these new areas.”
