Largest-ever marine reptile tooth discovered in the Swiss Alps

Life reconstruction of a giant ichthyosaur from the Late Triassic bulk-feeding on a school of squid. Marcello Perillo/ University of Bonn

A team of researchers have identified a 10cm long tooth discovered in the Swiss Alps as belonging to a giant marine reptile called the Ichthyosaur.

This is only the second time that such a large tooth has been attributed to an Ichthyosaur. Most of the larger specimens were toothless and sucked up their prey, unlike their smaller counterparts.

The incomplete tooth is part of a fossil find of three different Ichthyosaurs found in the Graubünden Alps in eastern Switzerland between 1976 and 1990. According to researchers from the Universities of Bonn and Zurich, one of them could have been as much as 15 metres in length. The creatures also had vertebrae and some ribs.

The root of the tooth is 6cm in diameter making it the thickest ichthyosaur tooth ever found. Rosi Roth/University of Zurich

Ichthyosaurs appeared 250 million years ago, when 95% of all marine species had disappeared. They were fish eaters and had to surface to breathe like today’s dolphins and whales.

Giant forms appeared 200 million years ago, before their progressive extinction. The largest, Shastasaurus sikanniensis,  was 21 metres long and found in British Columbia in Canada.

The sites where these fossils were found in Graubünden are part of a stratigraphic unit in the eastern Alps called the Kössen Formation, which extends to eastern Austria. The sediments were accumulated in the Triassic period (250 to 200 million years ago), when the Thetys Ocean covered large parts of the area.

At that time, this was a flat coastal region that was not very suitable for fast-moving marine reptiles that could weigh several tens of tons. Some of them probably beached here.