Agardhfjellet Formation

Pliosaurus is the type genus (defining example) of the pliosaurs, one of the major group of the plesiosaurs, an extinct group of aquatic marine reptiles. It lived from the Upper Jurassic to the Lower Cretaceous in what is now Europe and South America. The first known fossil consists of a partial skeleton of an immature specimen collected by William Buckland in Market Rasen, England. Although initially mentioned in a 1824 paper by William Daniel Conybeare, it was not until 1841 that it was first formally described by Richard Owen as belonging to a new species of Plesiosaurus, before being given

Colymbosaurus is a genus of cryptoclidid plesiosaur from the Middle-Late Jurassic (Callovian-Tithonian) of the UK and Svalbard, Norway. There are two currently recognized species, C. megadeirus and C. svalbardensis.

Spitrasaurus is an extinct genus of cryptoclidid plesiosauroid plesiosaur known from the uppermost Jurassic of central Spitsbergen, Norway and likely also Kimmeridge, England. It is named after a syllabic abbreviation for Spitsbergen Travel. Two species have been named: Spitrasaurus wensaasi, honouring volunteer Tommy Wensås, and Spitrasaurus larseni honouring volunteer Stig Larsen.

Djupedalia is an extinct genus of cryptoclidid plesiosauroid plesiosaur known from the uppermost Jurassic of central Spitsbergen, Norway. It is named after Øystein Djupedal, the former Minister of Education and Research who helped fund the fossil excavation with a budget of 1.2 million Norwegian kroner.

Janusaurus is an extinct genus of ophthalmosaurid ichthyosaur 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 long. In 2019, Janusaurus was synonymized with Arthropterygius, though maintained as a separate species, by Nikolay Zverkov and Natalya Prilepskaya, 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.

Ophthalmothule (meaning "eye of the north"), was a cryptoclidid plesiosaur dating to the latest Volgian (around the Jurassic-Cretaceous boundary), found in the Slottsmøya Member Lagerstätte of the Agardhfjellet Formation in Spitsbergen. The type species is O. cryostea.

Palvennia is an extinct genus of ophthalmosaurid ichthyosaurian known from the uppermost Jurassic of Central Spitsbergen, Norway. It was named for PalVenn, the Friends of the Palaeontological Museum in Oslo, whose expedition led to the discovery of the type specimen. Palvennia was a medium-sized ichthyosaur, measuring long. It was originally known from a single skull from the Slottsmøya Member of the Agardhfjellet Formation (middle Volgian/late Tithonian, Late Jurassic) that measures long. It is unusual in having a very short rostrum (~0.6× the skull length), similar to Ichthyosaurus breviceps

Arthropterygius is a widespread genus of ophthalmosaurid ichthyosaur which existed in Canada, Norway, Russia, and Argentina from the late Jurassic period and possibly to the earliest Cretaceous.

REDIRECT Undorosaurus#Cryopterygius

Nannopterygius (meaning "small wing/flipper" in Greek) is an extinct genus of ophthalmosaurid ichthyosaur that lived during the Middle Jurassic to the Early Cretaceous (Callovian to Berriasian stages). Fossils are known from England, Kazakhstan, Russia, and Norway and six species are currently assigned to the genus.

Keilhauia is a genus of ophthalmosaurid ichthyosaur, a type of dolphin-like, large-eyed marine reptile, from the Early Cretaceous shallow marine Slottsmøya Member of the Agardhfjellet Formation in Svalbard, Norway. The genus contains a single species, K. nui, known from a single specimen discovered in 2010 and described by Delsett et al. in 2017. In life, Keilhauia probably measured approximately in length; it can be distinguished by other ophthalmosaurids by the wide top end of its ilium and the relatively short ischiopubis (the fusion of the ischium and the pubis) compared to the femur. Alth