Ischyrodon

Ischyrodon (meaning 'strong tooth') is a dubious genus of large pliosaurid plesiosaur from the Middle Jurassic of Switzerland. The only known species is I. meriani, originally mentioned in 1838 by Hermann von Meyer from a large tooth discovered in Wölflinswil, before being first described in detail by the same author in 1856. The taxon remained valid until 1889, when Richard Lydekker synonymized it with a large species of Pliosaurus. However, in 1960, Lambert Beverly Tarlo noted that the tooth shares more similarities with those of Liopleurodon, instead considering it as a synonym of this latter, a view that was later largely followed in scientific literature. However, a 2022 revision found few differences that would allow it to be distinguished from Liopleurodon and other thalassophonean pliosaurids, then considering it as a nomen dubium.