Conspecific Fight in the Prehistoric Sea

Ichthyosaur fossil discovered with bite marks of a conspecific in Australia

Reconstruction of a Platypterygius © Josh Lee (Adelaide)
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Life in the primeval oceans was anything but a pony farm: researchers discovered deep fissures on the jawbone of a 120 million year old marine reptile. They show how fiercely the fight for survival raged in the polar seas back then. The bite marks are not from a predator, but probably from a conspecific, inflicted in the fight for food, partner or the territory.

About 120 million years ago, Australia and the Antarctic were still connected and formed a common southern continent. The now dry-hot inner part of Australia at that time formed the reason of a huge polar inland sea with cold water and even some icebergs. In the Cretaceous, ichthyosaurs, dolphin-like marine reptiles that fed on fish and squid-like animals, lived in this shallow sea.

Bite marks are evidence of battle for food, partner or territory

Now a research team from the Universities of Adelaide in Australia and Uppsala in Sweden near the city of Marree in central Australia has discovered a fossil of such an ichthyosaur, which has a whole series of bite marks on its jawbone. The approximately five-meter-long specimen of a Platypterygius was anything but defenseless with its long snout and more than 100 sharp, crocodile-like teeth. But the wounds, which apparently healed again during the animal's lifetime, bear witness to at least one fierce attack.

Bite traces of a fellow-member on the jaw of the ichthyosaur © Jo Bain, South Australian Museum

From the close distance of the tooth tracks and the position of the wounds on the mouth of the ichthyosaur, the researchers conclude that this may not have been an attack by a predator. The defense of a prey animal, they consider unlikely. Instead, the evidence points to the fact that there must have been a struggle here between conspecifics - for food, mating partners or the territory. In such intraspecies battles many species target their bites on the jaw and snout region of the enemy to prevent them from biting back.

Insight into the social behavior and environment of polar ichthyosaurs

The traces of bites now discovered on the ichthyosaur skeleton are the first indications that such behavior may have occurred even in the Cretaceous and ichthyosaurs. "Pathological traces on fossilized bones and teeth give us unique insights into the lives and social behavior of extinct animals, " explains Benjamin Kear, palaeontologist at Uppsala University in Sweden, Such findings have been rare in ichthyosaurs before. The details of the fund will be published in the next issue of the journal Acta Palaeontologica Polonica . (Acta Palaeontologica Polonica, 2011; doi: 10.4202 / app.2010.0117) Display

(Uppsala University, 09.05.2011 - NPO)