Elasmosauridae is an extinct family of plesiosaurs, often called elasmosaurs. They had the longest necks of the plesiosaurs and existed from the Hauterivian to the Maastrichtian stages of the Cretaceous, and represented one of the two groups of plesiosaurs present at the end of the Cretaceous alongside Polycotylidae.
Umoonasaurus is an extinct genus of plesiosaur belonging to the family Leptocleididae. This genus lived approximately 115 million years ago during the Early Cretaceous period, in shallow seas covering parts of what is now Australia. It was a relatively small animal around 2.5 metres (8.2 ft) long. An identifying trait of Umoonasaurus is the presence of three crest-ridges on its skull.
Plesiopleurodon is an extinct genus of Mesozoic marine reptiles, belonging to the Sauropterygia, known from the Late Cretaceous of North America. It was named by Kenneth Carpenter based on a complete skull with a mandible, cervical vertebra, and a coracoid. In naming the specimen, Carpenter noted "Of all known pliosauroids, Plesiopleurodon wellesi most closely resembles Liopleurodon ferox from the Oxfordian of Europe, hence the generic reference." It was initially described as a pliosauroid due to it short neck, a common trait of the superfamily. However, later exploration into the relationships of both groups indicate that not all pliosauroids have short necks and not all plesiosauroids have long necks. Later research indicates it is a member of the Polycotylidae, within the clade Occultonectia.
Pliosaurus is an extinct genus of thalassophonean pliosaurid known from the Late Jurassic of Europe and South America. Most European species of Pliosaurus measured around 8 metres (26 ft) long and weighed about 5 metric tons, but P. rossicus and P. funkei would have been one of the largest plesiosaurs of all time, exceeding 10 metres (33 ft) in length. This genus has contained many species in the past but recent reviews found only six to be valid, while the validity of two additional species awaits a petition to the International Code of Zoological Nomenclature. Currently, P. brachyspondylus and P. macromerus are considered dubious, while P. portentificus is considered undiagnostic. Species of this genus are differentiated from other pliosaurids based on seven autapomorphies, including teeth that are triangular in cross section. Their diet would have included fish, cephalopods, and marine reptiles.
Picrocleidus is an extinct genus of plesiosaur from the Middle Jurassic Oxford Clay Formation of the United Kingdom.
Kimmerosaurus is an extinct genus of plesiosaur from the family Cryptoclididae. Kimmerosaurus is most closely related to Tatenectes.
Colymbosaurus is a genus of cryptoclidid plesiosaur from the Late Jurassic (Callovian-Tithonian) of the UK and Svalbard, Norway. There are two currently recognized species, C. megadeirus and C. svalbardensis.
Nannopterygius is an extinct genus of ophthalmosaurid ichthyosaur that lived during the Middle Jurassic to the Early Cretaceous. Fossils are known from England, Kazakhstan, Russia, and Norway and six species are currently assigned to the genus.
Bathyspondylus is an extinct genus of plesiosaur from the Kimmeridge Clay Formation of Swindon, England. Because it is known only from its fossil vertebrae, paleontologists are not entirely sure of the taxonomy of Bathyspondylus; the family it belongs to is not currently known. The type, and only known, species is B. swindoniensis, which was described from the same material as its genus.
Tricleidus is an extinct genus of cryptoclidid plesiosaur known from only specimen from the middle Jurassic of United Kingdom. It was first named by Andrews in 1909 and the type species is Tricleidus seeleyi.
Abyssosaurus is an extinct genus of cryptoclidid plesiosaur known from the Early Cretaceous of Chuvash Republic, western Russia. It possessed a shortened skull, and it has been suggested that it primarily inhabited the bathyal zone.
Stratesaurus is an extinct genus of small-bodied rhomaleosaurid plesiosaur known from the Early Jurassic period of the United Kingdom. It contains a single species, S. taylori. It was a small plesiosaur, with a skull length of 18 cm (7.1 in) and a body length of 2 m (6.6 ft).
Eoplesiosaurus is an extinct genus of basal plesiosauroid known from the Early Jurassic period of the United Kingdom. It contains a single species, E. antiquior.
Microcleididae is an extinct family of basal plesiosauroid plesiosaurs from the Early Jurassic of France, Germany, Portugal and the United Kingdom. Currently, the oldest and the most known microcleidid is Eretmosaurus from the middle Sinemurian of the United Kingdom. Microcleididae was formally named and described by Roger B. J. Benson, Mark Evans and Patrick S. Druckenmiller in 2012.
Anningasaura is an extinct genus of basal plesiosaur. It is known from a single type species, A. lymense, discovered in Early Jurassic rocks of Lyme Regis in the United Kingdom.
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.
This timeline of plesiosaur research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, taxonomic revisions, and cultural portrayals of plesiosaurs, an order of marine reptiles that flourished during the Mesozoic Era. The first scientifically documented plesiosaur fossils were discovered during the early 19th century by Mary Anning. Plesiosaurs were actually discovered and described before dinosaurs. They were also among the first animals to be featured in artistic reconstructions of the ancient world, and therefore among the earliest prehistoric creatures to attract the attention of the lay public. Plesiosaurs were originally thought to be a kind of primitive transitional form between marine life and terrestrial reptiles. However, now plesiosaurs are recognized as highly derived marine reptiles descended from terrestrial ancestors.
The Agardhfjellet Formation is a geologic formation in Svalbard, Norway. It preserves fossils dating back to the Oxfordian to Berriasian stages, spanning the Late Jurassic-Early Cretaceous boundary. The formation contains the Slottsmøya Member, a highly fossiliferous unit (Lagerstätte) where many ichthyosaur and plesiosaur fossils have been found, as well as abundant and well preserved fossils of invertebrates.
Patrick Scott Druckenmiller is a Mesozoic paleontologist, taxonomist, associate professor of geology, Earth Sciences curator, and museum director of the University of Alaska Museum of the North, where he oversees the largest single collection of Alaskan invertebrate and vertebrate fossils. He has published work on plesiosaurs, ichthyosaurs, mastodons, and dinosaurs in the United States, Svalbard, and Canada. He has co-authored papers on discussions of mass extinctions and biogeography. Much of his work has focused on Arctic species. He is a member of the Spitsbergen Jurassic Research group, which focuses on marine reptiles.
