Paleontologists in Switzerland have unearthed an exceptionally rare fossil jaw of an ancient creature known as a pliosaur.

Pliosaurs were a type of short-necked plesiosaur: marine reptiles built for speed compared to their long-necked cousins.

They lived between 220 million years ago (Triassic period) and 70 million years ago (Cretaceous period) and were mostly found in the prehistoric seas that covered modern-day Europe.

Also known as pliosauroids, pliosaurs were not dinosaurs, but distant cousins of modern turtles.

They had four powerful flipper-like limbs, large crocodile-like heads, extremely powerful jaws and enormous teeth, and hunted fish, cephalopod mollusks and other marine reptiles. They reached lengths of up to 50 feet (15 m), which exceeds the size of the largest toothed whales today.

“Pliosaurs were amongst the largest marine animals of their time, and were at the top of the food chain,” said Dr. Sven Sachs, a researcher at the Natural History Museum Bielefeld.

In a new study, Dr. Sachs and his colleagues from Switzerland and Sweden analyzed a partial jaw of a large-bodied plesiosaur that lived during the Jurassic period.

The specimen was collected by the fossil enthusiast Dr. Hans Holenweg from the Passwang Formation near Arisdorf in the Basel-Land canton of Switzerland.

“At around 170 million years old, the Arisdorf jaw represents one of the oldest occurrences of very large pliosaur apex predators in the fossil record, and may have come from an animal that was around 30 feet (9 m) long,” said Dr. Benjamin Kear, a paleontologist at Uppsala University.

Only the rear section of the Arisdorf jaw was recovered, but it has a total length of 1.6 feet (0.5 m).

The paleontologists estimate that the jaw was approximately 5 feet (1.5 m) long when complete.

“The Arisdorf pliosaur is the first find of its kind from Switzerland, and comes from a geological timeframe with a hitherto very sparse fossil record of pliosaurs and their relatives,” said Dr. Christian Klug, a scientist at the University of Zurich.

The study was published in the Swiss Journal of Palaeontology.

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S. Sachs et al. Rare evidence of a giant pliosaurid-like plesiosaur from the Middle Jurassic (lower Bajocian) of Switzerland. Swiss J Palaeontol, published online November 1, 2019; doi: 10.1007/s13358-019-00200-9