Evrim Yazgin
Cosmos science journalist
About 20 million years ago, one dugong had a very rough day indeed.
The ancient sea cow’s fossil shows evidence of bite marks not just from one nightmarish predator, but two – a crocodile and a shark.
Discovered in northwestern Venezuela, analysis of the fossil of the dugongine sea cow belonging to the extinct genus Culebratherium is published in the Journal of Vertebrate Paleontology.
It was discovered 100 kilometres away from known fossil sites.
Today, dugongs are one of four species of sirenian aquatic mammals – the other 3 are manatees. The closest relative of modern dugongs is the now extinct Steller’s sea cow.
Finding fossils which show predation is rare. Only a few examples of this exist dating back to the early to middle of the Miocene epoch (23–5 million years ago). Such finds can give a unique insight into the life and death of animals which lived millions of years ago.
Palaeontologists studying the sea cow’s remains found deep tooth marks on the animal’s snout. These, caused by a crocodilian, suggest the predator tried to suffocate its prey.
Further large incisions show the crocodile then dragged the sea cow and tore flesh away.
Marks on the 20-million-year-old remains suggest the crocodile performed a “death roll” – a behaviour common in modern crocodilians.
But that wasn’t all for the luckless sea cow.
The researchers also found bite marks from a shark. A tooth lodged in the dugong’s rib cage allowed the palaeontologists to solve the ancient whodunnit, determining that the shark which also feasted on the sea cow was a tiger shark (Galeocerdo aduncus) – a species which appears in the fossil record as early as 50 million years ago and has remained unchanged to this day.
The ancient interplay uncovered between predator and prey suggests the food chain millions of years ago functioned much as it does today.
“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 lead author Aldo Benites-Palomino from the University of Zurich, Switzerland.
“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.”
The find is one of only a few which shows predation by multiple different predators in the fossil record.
