Monster swallows monster: fossil reveals doubly fatal Triassic encounter

California, US: In a warm shallow sea about 240 million years ago in what is now southwestern China, a large dolphin-like marine reptile attacked and swallowed an almost equally big lizard-like marine reptile in a savage encounter that left both beasts dead.

Scientists on Thursday described a fossil unearthed in China's Guizhou Province that reveals this Triassic Period drama in exceptional detail and changes the understanding of "megapredation" in prehistoric seas. While it long has been presumed that large apex predators preyed upon other big animals - megapredation is defined as feeding on prey of human size or larger - the Chinese fossil represents the first direct evidence of it, as demonstrated by a prehistoric animal's stomach contents.

The fossil shows the skeleton of a 15-foot-long (5 meters) Guizhouichthyosaurus, a type of marine reptile called an ichthyosaur. Its body design married elements of a dolphin and a tiger shark though it lacked a dorsal fin, also boasting four strong flippers and a mouth full of powerful but blunt teeth.

Inside its stomach was the torso of a 12-foot-long (4 meters) Xinpusaurus, a type of marine reptile called an a thalattosaur. Its body design resembled a komodo dragon with four paddling limbs and teeth equipped for crushing shells. The Xinpusaurus was beheaded in the melee and its tail severed.

The Guizhouichthyosaurus literally may have bitten off more than it could chew. "There was a fight between the two and that must have been pretty fierce," said paleobiologist and study co-author Ryosuke Motani of the University of California, Davis.

"This predator is not a snake, so it's not as good as as good at swallowing so you have to use the inertia or maybe use the gravity to push it (prey) down ... when you do that, you don't have total control and could easily explain the damage of the neck," added Motani. The fossil bore evidence of this broken neck. The prey in the stomach showed little signs of digestion, indicating the ichthyosaur died soon after swallowing it.

It is among the more dramatic fossils on record, joining others such as one showing the Cretaceous Period dinosaurs Velociraptor and Protoceratops locked in combat and another of the large Cretaceous fish Xiphactinus that had swallowed whole another sizeable fish.

Guizhouichthyosaurus was the largest-known marine predator of its time, about 10 million years before dinosaurs appeared. Its teeth, however, were not the type thought to be needed for megapredation: blunt rather than having cutting edges for slicing flesh.