|Cimoliasaurus magnus vertebrae.|
The name is derived from the Greek Κιμωλία/kimolia, meaning "white chalk", and σαύρος/sauros, meaning "lizard", in reference to the fact that the deposits in which it was found bear a superficial resemblance to the chalk deposits of the Western Interior Seaway.
In his catalogue of plesiosaur and ichthyosaur specimens preserved in the NHM, the British zoologist Richard Lydekker referred several Jurassic and Cretaceous plesiosaur species to Cimoliasaurus, including the new species C. richardsoni (now considered a species of Cryptoclidus) and C. cantabrigiensis, as well as Colymbosaurus and a number of previously described species from the Cambridge Greensand and Chalk Group.
The Aristonectidae is a taxonomic family of poorly known plesiosaurs from the Jurassic and Cretaceous periods. They are closely related to polycotylid plesiosaurs. The family is made up of Tatenectes, Kimmerosaurus, Aristonectes, and Kaiwhekea. This group was formerly known as the Cimoliasauridae, but since Cimoliasaurus is indeterminate and quite possibly elasmosaurid, this replacement name was erected.
Tatenectes and Kimmerosaurus represent an earlier Oxfordian Jurassic radiation from Laurasia, while Aristonectes and Kaiwhekea represent a later Cretaceous radiation from Gondwana.Aristonectinae
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.Brimosaurus
Brimosaurus (meaning "strong lizard") is an extinct genus of plesiosaur from the Late Cretaceous of what is now Arkansas. The type species is Brimosaurus grandis, first named by Joseph Leidy in 1854. The name Brimosaurus is a nomen dubium: the fossils consist of only a few isolated vertebrae, and in 1952 Welles proposed that Brimosaurus was actually synonymous with Cimoliasaurus (which itself is based on dubious material).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).Discosaurus
Discosaurus is an extinct genus of Cretaceous plesiosaur first discovered in Alabama by Joseph Leidy. It was argued to be the same animal as Elasmosaurus.Elasmosauridae
Elasmosauridae was a family of plesiosaurs. They had the longest necks of the plesiosaurs and survived from the Late Triassic to the end of the Cretaceous. Their diet mainly consisted of crustaceans and molluscs.Elasmosaurus
Elasmosaurus (;) is a genus of plesiosaur that lived in North America during the Campanian stage of the Late Cretaceous period, about 80.5 million years ago. The first specimen was discovered in 1867 near Fort Wallace, Kansas, and was sent to the American paleontologist Edward Drinker Cope, who named it E. platyurus in 1868. The generic name means "thin-plate reptile", and the specific name means "flat-tailed". Cope originally reconstructed the skeleton of Elasmosaurus with the skull at the end of the tail, an error which was made light of by the paleontologist Othniel Charles Marsh, and became part of their "Bone Wars" rivalry. Only one incomplete Elasmosaurus skeleton is definitely known, consisting of a fragmentary skull, the spine, and the pectoral and pelvic girdles, and a single species is recognized today; other species are now considered invalid or have been moved to other genera.
Measuring 10.3 meters (34 ft) long, Elasmosaurus would have had a streamlined body with paddle-like limbs, a short tail, a small head, and an extremely long neck. The neck alone was around 7.1 meters (23 ft) long. Along with its relative Albertonectes, it was one of the longest-necked animals to have lived, with the largest number of neck vertebrae known, 72. The skull would have been slender and triangular, with large, fang-like teeth at the front, and smaller teeth towards the back. It had six teeth in each premaxilla of the upper jaw, and may have had 14 teeth in the maxilla and 19 in the dentary of the lower jaw. Most of the neck vertebrae were compressed sideways, and bore a longitudinal crest or keel along the sides.
The family Elasmosauridae was based on the genus Elasmosaurus, the first recognized member of this group of long-necked plesiosaurs. Elasmosaurids were well adapted for aquatic life, and used their flippers for swimming. Contrary to earlier depictions, their necks were not very flexible, and could not be held high above the water surface. It is unknown what their long necks were used for, but they may have had a function in feeding. Elasmosaurids probably ate small fish and marine invertebrates, seizing them with their long teeth, and may have used gastroliths (stomach stones) to help digest their food. Elasmosaurus is known from the Pierre Shale formation, which represents marine deposits from the Western Interior Seaway.Hastanectes
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.Hydrorion
Hydrorion (meaning 'water hunter') is an extinct genus of plesiosaur. It was found in Jurassic formations in Germany to Posidonia Shale formation.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.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.Styxosaurus
Styxosaurus is a genus of plesiosaur of the family Elasmosauridae. Styxosaurus lived during the Campanian age of the Cretaceous period.Tatenectes
Tatenectes is an extinct genus of cryptoclidid plesiosaur known from the Upper Member of the Sundance Formation (late Jurassic) of Wyoming. It was named by O'Keefe and Wahl in 2003 and the type species is Tatenectes laramiensis.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.