More than 230 million years ago, a giant dolphin-like marine reptile, known as an ichthyosaur, forgot its finite meal – a creature almost its own size – and died a short time later.
Inside his abdomen was the body of a lizard-like egg white reptile called a thalattosaur, adorned with its head and long tail, but undigested.
Paleontologists digging in a quarry in southwest China were surprised to discover the remains in 2010: it is almost uncommon to find the stomach contents of marine fossils.
A decade on, in a paper published in iScience On Thursday, researchers concluded that instead of feeding on much smaller kephalopods such as squid, the five-meter-long ichthyosaur was probably a mega-predator.
What’s more, this particular specimen might have died while picking up its prey, literally biting more than it could chew.
“The most likely cause of death is the neck fracture, which probably prevented the predator from breathing,” co-author Ryosuke Motani, a paleobiologist at the University of California, Davis told AFP.
The ichthyosaur may have sustained injuries while fighting the thalattosaur, he added, or while trying to swallow it – if both.
But, Motani warned: “The interpretation of the death process involves speculation, because no one was there to film it for us.”
Also read: Fossil of one of the last megaraptors found on the planet in Argentina
Crocodile-like teeth
The team is a little more confident that the thalattosaur, which was slightly smaller than its enemy at four meters in length, hit a violent end, instead of being scavenged to stars of natural causes.
“There are no signs of prey rats – if it was a rotten carcass, you would not expect the fingers to attach to the body yet,” Motani said.
The detached tail of the thalattosaurus was found 20 meters away, leading the team to believe that it was ripped off and left behind by the ichthyosaur.
The stomach contents of the ichthyosaur show no signs of advanced digestion by acid, which means that it probably died shortly after its final meal.
“At first we just did not believe it, but after several years of visiting the dig site and looking at the same specimens, we finally knew what we were seeing,” Motani added.
Because the discovery of stomach contents in marine fossils is so rare, scientists generally rely on teeth and jaw shapes to distinguish what they may have eaten.
Ancient apex predators are typically thought to have had large, very sharp teeth – although some modern predators such as crocodiles use blunt teeth to consume large prey with gripping force instead of cutting.
Ichthyosaurs have blunt teeth, but because there was no direct evidence of large prey consumption, researchers previously thought they should feed on small prey.
“Now, we can seriously consider that (Ichthyosaurs) ate large animals, even when they had teeth,” Motani added.
These events took place after the end of the Permian period, about 250 million years ago, when terrestrial vertebrates began to move to the sea after an event in mass extinction.
The fact that predators emerged shortly thereafter in the Middle Triassic was a sign that ecosystems were bouncing back, Motani said.
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