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The bones of three ichthyosaurs – huge marine reptiles that roamed primordial waters – were unearthed high in the Swiss Alps, including the biggest ever tooth known for the species, according to research published Thursday.

The specimens were discovered during geological investigations between 1976 and 1990 but were just recently thoroughly investigated.

The prehistoric leviathans weighed up to 88 tons and grew to 20 meters long, which makes them the largest animals to have ever existed.

They originally originated in the early Triassic period 250 million years ago, and a smaller, dolphin-like variety lived until 90 million years ago. However, the vast majority of the species, the ichthyosaurs, went extinct 200 million years ago.

According to Martin Sander of the University of Bonn, the paper's lead author in the Journal of Vertebrate Paleontology, unlike dinosaurs, ichthyosaurs left behind no fossil remains, which he describes as "a great mystery."

They were discovered at a height of 2,800 meters. The three swam in the waters around the supercontinent Pangea throughout their lives, but the fossils kept rising owing to plate tectonics and the folding of the Alps.

Previously, it was considered that ichthyosaurs exclusively lived in the deep ocean, but the rocks from which the new fossils were discovered are thought to have been at the bottom of a shallow coastal region. Some of the giants may have followed schools of fish there.

There are two distinct groups of skeletal remains. One consists of 10 rib pieces and a vertebra, implying a 20-meter-long animal, about comparable to the biggest ichthyosaur yet discovered in Canada.

According to the seven vertebrae discovered, the second animal measured 15 meters.

Sander divulged that the tooth, "is particularly exciting," due to it being "huge by ichthyosaur standards: Its root was 60 millimeters (2.4 inches) in diameter - the largest specimen still in a complete skull to date was 20 millimeters and came from an ichthyosaur that was nearly 18 meters long."

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While this may imply a monster of epic proportions, it's more likely to have originated from an ichthyosaur with exceptionally massive teeth than a very enormous ichthyosaur.

According to current studies, severe gigantism is incompatible with a predatory lifestyle that necessitates the use of teeth.

Sanders said that as a result, "Marine predators therefore probably can't get much bigger than a sperm whale," adding that more fossils would need to be found to be absolutely sure.