The discovery of an aquatic reptile in the fossilized belly of an ichthyosaur is the first scientific evidence that these giants were mega-predators.
When paleontologists excavating a quarry in southwest China discovered the nearly complete skeleton of an ichthyosaur – a giant dolphin-like marine reptile – they didn’t expect to find an incredible surprise inside. Inside its stomach they found a second fossil, the skeleton of a thalatosaurus – another aquatic reptile, similar to a lizard, of four meters – one of the longest remains ever found in the stomach of a prehistoric marine reptile .
While the researchers can’t say for sure whether the thalatosaurus was abducted or eaten, their work could be the oldest direct evidence that Triassic marine reptiles like ichthyosaurs, previously thought to feed on cephalopods, were apex mega-predators. . The study has just been published in the journal ” iScience “.
“If you look at all the similar marine reptiles that lived in the age of dinosaurs , we’ve never actually found anything like this articulated in the stomach,” says research co-author Ryosuke Motani , a professor of paleobiology at the University of California. ‘The stomach contents of our ichthyosaur were not damaged by stomach acid , so it must have died shortly after ingesting this food. At first we just didn’t believe it, but after spending several years visiting the excavation site and looking at the same specimen, we were finally convinced of what we saw.
The contents of the stomach is rarely found in marine fossils. For this reason, researchers are based on the shapes of teeth and jaws to find out which species could serve as food. While prehistoric predators are believed to have large teeth with sharp cutting edges, some current predatory species, such as crocodiles , use blunt teeth to eat large prey, taking advantage of their gripping rather than cutting force. Ichthyosaurs share these blunt teeth, but without direct evidence of heavy prey consumption in these prehistoric marine reptiles, scientists believed that they preyed on small animals, such as cephalopods .
However, the discovery of the giant thalatosaurus in the ichthyosaur stomach found by Motani together with Peking University paleontologist Da-Yong Jiang , suggests that this was not the case. “Now, we can seriously consider that they were eating large animals, even when they had blunt teeth . It’s pretty clear that this animal could process this large feed using blunt teeth, ”says Motani.
What researchers still don’t know is whether the ichthyosaur hunted the thalatosaurus or gobbled it up once dead . However, there is reason to believe that it was not a scavenger: marine decomposition studies suggest that if the inert body had been on the seabed, the limbs would have detached and detached before the tail. Instead, the researchers found the opposite: the fins were at least partially attached to its body in the stomach, while a tail was found many meters away , leading researchers to believe that it was ripped off and abandoned by a predator, such as the ichthyosaur.
Whether or not the ichthyosaur killed its Last Supper, the fossil provides the oldest direct evidence that these giant marine reptiles consumed animals larger than humans. “We now have a solid articulated fossil in the stomach of a marine reptile for the first time,” says Motani. “This also suggests that megapredation was probably more common than we previously thought.”
The team is still excavating the site where the pair of fossils were found, which will now be displayed in a museum. “We have been digging in that particular quarry for over ten years and still new things keep coming out. We will have to see what new discoveries we will make in the future.