For its last meal, an ancient marine reptile called an ichthyosaur may have bitten off more than it could chew.
The dolphin-like creature was nearly five meters long, about the length of a canoe. And its belly contained the remains of a lizard-like reptile called a thalattosaur that was almost as long: four meters.
This is the longest known prey of a marine reptile from the dinosaur age, and may be the oldest direct evidence of a marine reptile eating an animal larger than a human, researchers from the University of California reported August 20 in iScience journal.
This particular thalattosaur may have been such a big meal that the ichthyosaur died after stomaching it, they said.
The ichthyosaur's blunt teeth suggest it should have favored small, soft prey like cephalopods. Now, the researchers have really solid evidence saying these blunt teeth can be used to eat something big.
During the study, Ryosuke Motani, a paleobiologist at the University of California, and his colleagues examined the nearly complete skeleton of an adult ichthyosaur that lived during the Triassic Period about 240 million years ago. Upon closer inspection of a big lump of bones in the creature's belly, Motani's team discovered that the last thing the ichthyosaur ate was the body of a thalattosaur.
The thalattosaur remains show little evidence of being degraded by stomach acid, suggesting the ichthyosaur died shortly after its enormous meal.
The researchers believe the ichthyosaur most likely hunted, rather than scavenged, its meal. For one thing, it would have been unusual to come across a whole dead animal that no other predator had gobbled up.
Plus, the thalattosaur's limbs were still at least partially attached to its body, while its tail was uncovered about 20 meters away.
Studies of how bodies decompose underwater suggest that if the thalattosaur was a carcass when the ichthyosaur found it, the prey's limbs would have rotted off before its tail, the authors argued.
The ichthyosaur's fossilized body and head, while well preserved, are detached from one another, hinting that the animal may have died of a broken neck. The ichthyosaur could have injured its neck while holding the thalattosaur in its jaws and thrashing its head, which is how crocodiles and killer whales rip up their food without particularly sharp teeth.
