Janusaurus is an extinct genus of ophthalmosauridichthyosaur from the Upper Jurassic Slottsmøya
Member, Agardhfjellet Formation of Central Spitsbergen. The holotype consists of a partial skull and postcrania, and would have belonged to an individual measuring 3–4 m (9.8–13.1 ft) long.[2] In 2019, Janusaurus was synonymized with Arthropterygius, though maintained as a separate species, by Nikolay Zverkov and Natalya Prilepskaya,[3] although this synonymy was objected to later that same year by Lene Delsett and colleagues, who maintained that they were sufficiently different to warrant separate genera.[4]
