A team of paleontologists has found the nearly complete skeleton of a four-meter thalatosaurus in the stomach of a five-meter ichthyosaur.

The image shows the contents of the stomach of the ichthyosaur, which contains the almost complete skeleton of a thalatosaurus

When paleontologists in a quarry excavation in southwest China recovered the complete skeleton of un ictiosaurio –A giant marine reptile very similar to today’s dolphins– the last thing they expected to find was another fossil in the stomach of this specimen. The second vestige was part of the skeleton of a thalatosaurus four-meter-long, another lizard-like aquatic reptile and one of the largest fossils ever found in the stomach of a prehistoric marine reptile.

Although the researchers cannot determine whether the thalatosaurus was hunted or consumed as a corpse, this finding collected in the last issue of iScience may be direct proof that Triassic marine reptiles, such as the ichthyosaurs, they were super predators –The top of the food chain, without having a predator capable of hunting them– and they did not feed only on cephalopods, as was believed until now.

Ryosuke Motani, co-author of the work and professor of paleobiology at the University of California at Davis (USA), assures SINC that it has never been found nothing like it in a marine reptile from the time of the dinosaurs: “When we looked at the specimen after preparing it, we were puzzled by the block of stone protruding from the belly. This state of preservation is unusual and we weren’t even sure if it was a geological structure or something in the stomach. “

The researcher details that it took about seven years of visits to the excavation and comparison with other specimens until they could digest what they had found. One of the reasons for this delay is because the prey species, Xinpusaurus, it was unknown to science at the time.

Thus, Motani points out that this banquet could have been the last supper of this predator because the contents of the ichthyosaur’s stomach were not corroded by stomach acid, so it may have died shortly after eating this food. The main hypothesis of death is supported by the unusual size of the dam, which measured about four meters when it does not usually exceed three. “The ichthyosaur could have attacked without realizing this detail, which was what ultimately caused the death,” he postulates.

An unusual denture

Because they are rarely found in the stomach of marine fossils, researchers determine how these species fed through the shape of the teeth and jaw.

Prehistoric super predators usually have large and sharp teeth, although there are more current species – such as crocodiles – that use their blunt teeth to consume their prey using gripping force instead of chopping them.

Ichthyosaurs have these blunt teeth, but there was no evidence that they consumed large animals, so scientists believed that their diet was based on small species such as cephalopods.

However, the discovery of this giant thalatosaurus in the stomach of the ichthyosaur by Motani and Da-Yong Jiang’s team, a paleontologist from Peking University (China), raises a new scenario.

“We can consider that [los ictiosaurios] they fed on large animals, even with its blunt teeth. It had already been suggested that sharp teeth would not have to be crucial for digesting huge foods and our discovery goes in that direction ”, says Ryosuke Motani.

The paleontology professor acknowledges that finding direct evidence like the one in this work is a matter of luck and, therefore, no other fossil reptile has been found showing stomach contents with this good state of preservation. For this to happen, “the predator must die shortly after ingesting its food to stop digestion,” he says.

Scavenger or hunter?

Researchers are now aware that the ichthyosaur could eat animals as large as this four-meter thalatosaurus. But cannot determine if it is scavenging behavior -He ate the corpse of this reptile- or saucepan.

However, there are reasons to believe that this it was not a case of necrophagia. As explained by the team of paleontologists, recent studies on marine decomposition suggest that, if it had been from a corpse, the limbs of the thalatosaurus would have disintegrated and uncoupled before the tail.

Research has found just the opposite in these fossils: the limbs of this animal were partially coupled to the body of the stomach, while the tail was separated several meters away. The team believes that it may have been ripped from the body by a predator such as the ichthyosaur.

Although it is not confirmed that this animal hunted its last prey, this fossil is the oldest direct evidence that these giant marine reptiles consumed animals larger than humans. This finding, Motani adds, suggests that the super predation was more common than previously thought.

The investigation team is still conducting excavation work at the quarry where the remains were found, which has now become part of the Xingyi Geopark from China. “We have been digging for over ten years and new objects keep popping up: from ammonites to fish and reptiles. We have already exceeded our initial expectations and this study is just a sample of the valuable information that we are finding ”, concludes the professor of paleontology.