Hastanectes is an extinct genus of a plesiosaurian with possible pliosaurid affinities known from the Early Cretaceous Wadhurst Clay Formation (Valanginian stage) of the United Kingdom. It contains a single species, Hastanectes valdensis, which was originally thought to be a species of Cimoliasaurus.
Temporal range: Early Cretaceous, Valanginian
Benson et al., 2012
Aristonectinae is a clade of plesiosaurs in the family Elasmosauridae. It includes the Late Cretaceous plesiosaurs Aristonectes and Kaiwhekea, traditionally grouped with the Late Jurassic Tatenectes and Kimmerosaurus in the family Aristonectidae. In recent years, multiple specimens were collected in Angola.Cimoliasaurus
Cimoliasaurus was a plesiosaur that lived during the Late Cretaceous (Maastrichtian) of New Jersey. It grew from 13 to 25 ft long.Cryptoclidia
Cryptoclidia is a clade of plesiosaurs.
Cryptoclidia was named and defined as a node clade in 2010 by Hilary Ketchum and Roger Benson: the group consisting of the last common ancestor of Cryptoclidus eurymerus and Polycotylus latipinnis; and all its descendants.The following cladogram follows an analysis by Benson & Druckenmiller (2014).Edgarosaurus
Edgarosaurus is a genus of polycotylid plesiosaur, containing one species, E. muddi. The type specimen was found in Early Cretaceous (late Albian) rocks in the state of Montana in the United States. At the time, this location was covered by part of the Western Interior Seaway.Fresnosaurus
Fresnosaurus is an extinct genus of plesiosaur from the Late Cretaceous (Maastrichtian stage) of what is now California. The type species is Fresnosaurus drescheri, first described by Welles in 1943. The generic name Fresnosaurus honors Fresno County, while the specific name honors Arthur Drescher.
Fresnosaurus was probably at least 30 feet in length. Like all elasmosaurid plesiosaurs, it probably ate small bony fish, belemnites, and ammonites.Hydrorion
Hydrorion (meaning 'water hunter') is an extinct genus of plesiosaur. It was found in Jurassic formations in Germany to Posidonia Shale formation.Kimmerosaurus
Kimmerosaurus ("lizard from Kimmeridge") is an extinct genus of plesiosaur from the family Cryptoclididae, closely related to Tatenectes.Macroplata
Macroplata (meaning "big plate") is an extinct genus of Early Jurassic basal plesiosaur which grew up to 4.5 metres (15 ft) in length. Like other plesiosaurs, Macroplata probably lived on a diet of fish, using its sharp needle-like teeth to catch prey. Its shoulder bones were fairly large, indicating a powerful forward stroke for fast swimming. Macroplata also had a relatively long neck, twice the length of the skull, in contrast to pliosaurs.Plesiosaurus longirostris was once assigned to this genus, but it has been re-assigned to Hauffiosaurus, as H. longirostris.Manemergus
Manemergus is a genus of polycotylid plesiosaur from the Late Cretaceous (Turonian) of Morocco. Manemergus was described in 2005 and contains only one species, M. anguirostris. The type specimen was discovered close to the town of Goulmima (Tizi-n-Imnayen) in Morocco's High Atlas mountains, in the same locality as another polycotylid, Thililua, was discovered.Maresaurus
Maresaurus is an extinct genus of pliosaur from the Middle Jurassic (Bajocian) of what is now Argentina. The type species, Maresaurus coccai, was named by Gasparini in 1997. Recent phylogenetic analysis found Maresaurus to be a rhomaleosaurid.Meyerasaurus
Meyerasaurus is an extinct genus of rhomaleosaurid known from Holzmaden, Baden-Württemberg of southwestern Germany.Orophosaurus
Orophosaurus is an extinct genus of plesiosaur.Picrocleidus
Picrocleidus is an extinct genus of plesiosaur. It is known only from the type species P. beloclis from the Middle Jurassic Oxford Clay Formation (Callovian stage) of the United Kingdom.Plesiopterys
Plesiopterys is an extinct genus of plesiosaur.Plesiosauridae
The Plesiosauridae are a monophyletic group of plesiosaurs.A family Plesiosauridae was first named by John Edward Gray in 1825.Seeleyosaurus
Seeleyosaurus is an extinct genus of plesiosaur. It is known from a large almost complete skeleton from the Upper Lias (Toarcian) of Württemberg, Germany. There seems to be the impression of a rhomboidal flap of skin in a vertical plane; if so, many plesiosaurs may have been equipped in this way.Thalassomedon
Thalassomedon (from Greek, thalassa, "sea" and Greek, medon, "lord" or "ruler", meaning "sea lord") is a genus of plesiosaur, named by Welles in 1943.Trinacromerum
Trinacromerum is an extinct genus of sauropterygian reptile, a member of the polycotylid plesiosaurs. It contains two species, T. bentonianum and T. kirki. Specimens have been discovered in the Late Cretaceous fossil deposits of what is now modern Kansas and Manitoba.Zarafasaura
Zarafasaura is an extinct genus of elasmosaurid known from the Oulad Abdoun Basin of Morocco.