Relics of an epic battle between the waves have been found on the jawbone of a 120 million-year-old sea monster.

The bite wounds inflicted on the ichthyosaur were probably made by a member of the same species, scientists believe.

Ichthyosaurs were dolphin-like marine reptiles that lived at the same time as the dinosaurs.

Adults grew to a length of six metres. The creatures were fierce predators with long-snouted heads and more than 100 pointed, crocodile-like teeth.

Scientists unearthed the fossil skeleton of an ichthyosaur in remote wasteland near the town of Marree in northern South Australia.

When the animal was alive, the Australian continent was still joined to Antarctica and much further south than it is today.

What is now arid grassland was then the bottom of a vast inland sea.

Cleaning and reassembly of the bones revealed the preserved bite marks on the ichthyosaur’s lower jaw.

Evidence of healing suggested that the creature survived the attack and for some time afterwards.

The find is described in a forthcoming issue of the journal Acta Palaeontologica Polonica.

Researcher Benjamin Kear, from Uppsala University in Sweden, said: “Pathological traces on ancient fossilised bones and teeth give unique insights into the lives and social behaviours of extinct animals.”