Kronosaurus May Have Eaten Ichthyosaur That Swallowed a Pterosaur

A roughly 12-metre Kronosaurus may have attacked and fed on an almost 7-metre ichthyosaur that had swallowed part of a pterosaur. Found in inland Australia, the fossil retains bite damage and stomach contents, creating an unusual food chain involving three large reptiles from the Cretaceous period.

How did scientists uncover this food chain?

Four amateur fossil hunters found the specimen near Richmond in Queensland, Australia, in 2019. Before specialists at the Kronosaurus Korner museum examined them, the sizeable rock and bone blocks were nicknamed “Bag of Bones”.

After more than 600 hours of preparation, the team uncovered a partially articulated ichthyosaur measuring nearly 7 metres long. Concretions near its skull appeared likely to contain delicate structures, so the researchers chose to investigate them without breaking open the rock.

• The fossil was found in inland Queensland;
• The central animal was a large ichthyosaur;
• Some of the bones remained connected;
• Blocks close to the skull contained preserved food remains;
• Large bite marks were visible on the skeleton.

What was inside the ichthyosaur’s stomach?

Neutron imaging allowed the team to inspect the concretions internally without harming the material. The scans revealed fish, squid-like cephalopods, shell fragments and part of the lower jaw of a pterosaur, a flying reptile that inhabited the same region.

Why were the remains identified as a meal?

The fragments were concentrated immediately behind the ichthyosaur’s skull, within the area occupied by its digestive system. Their location and mixed composition support the view that the concretions are fossilised stomach contents, rather than bones brought together by water.

The find provides the first known direct evidence of an ichthyosaur eating a pterosaur. The flying reptile may have been caught after landing on, or falling into, the sea, although the fossil cannot establish whether it was hunted alive or encountered after death.

• The remains lay in the position corresponding to the intestine;
• Several prey types occurred within the same block;
• Imaging identified the pterosaur’s jaw;
• Fish and cephalopods were also included in the meal;
• The concretion analysis did not destroy the material.

Which damage suggests a Kronosaurus attack?

The ichthyosaur had broken vertebrae, missing ribs and bones bearing substantial crushing marks. One vertebra still held a rib pressed against its fractured edge, suggesting that the carcass had been subjected to the force of huge jaws rather than merely damaged after burial.

Did the large predator really eat the ichthyosaur?

Researchers regard Kronosaurus queenslandicus as the most likely culprit, as no other known predator from the ancient Eromanga Sea had teeth and jaws capable of producing damage on that scale. The pliosaur could reach about 12 metres and sat at the top of the marine food chain, but this identification remains an interpretation based on the injuries because no tooth was lodged in the skeleton.

This Cretaceous fossil food chain records three levels of predation in a single discovery: the pterosaur was eaten by the ichthyosaur, which was subsequently probably attacked or consumed by the Kronosaurus. More than 100 million years ago, these animals shared the Eromanga Sea, a vast marine expanse covering part of what is now Australia.