| Picrocleidus Temporal range: Middle Jurassic, | |
|---|---|
 | |
| Fossils from both specimens of P. beloclis | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | † Sauropterygia |
| Order: | † Plesiosauria |
| Family: | † Cryptoclididae |
| Genus: | † Picrocleidus Andrews, 1910 |
| Type species | |
| †Muraenosaurus beloclis Seeley, 1892 | |
Picrocleidus is an extinct genus of plesiosaur from the Middle Jurassic Oxford Clay Formation (Callovian stage) of the United Kingdom.
The holotype was discovered in the Oxford Clay Formation in Peterborough, England and acquired by Alfred Nicholson Leeds. [1] [2] It was initially assigned to Muraenosaurus as M. beloclis by Seeley in 1892. [3] The specific name means "arrow clavicle", referring to the triangular interclavicula. M. beloclis was moved to its own genus Picrocleidus by Charles William Andrews in 1910. [2] [4] The generic name is derived from Greek pikros, "sharp", en kleis, "key", again referring to the clavicles.
Five specimens are known:
The holotype specimen BMNH R1965, a postcranial skeleton.
Specimen BMNH R3698, a skeleton with skull, including a complete tail.
Specimen BMNH R2429, an old individual consisting of anterior and posterior cervical vertebrae, pectorals and the first dorsal, some dorsal ribs, the shoulder-girdle, and the left humerus. [2]
Specimen BMNH R2739, consisting of a basisphenoid and parasphenoid, cervical vertebrae, sacrals with the sacral ribs, an anterior caudal, some ventral ribs, both radii, odd paddle-bones, portions of ilia, ischia, and pubes. [1]
Specimen HM 2981666: a young individual.
Picrocleidus has previously been considered synonymous with Muraenosaurus although there are doubts in the relationship between the two groupings. [5]
Picrocleidus is currently classified as a member of the Cryptoclididae. [4]
Plesiosaurus is a genus of extinct, large marine sauropterygian reptile that lived during the Early Jurassic. It is known by nearly complete skeletons from the Lias of England. It is distinguishable by its small head, long and slender neck, broad turtle-like body, a short tail, and two pairs of large, elongated paddles. It lends its name to the order Plesiosauria, of which it is an early, but fairly typical member. It contains only one species, the type, Plesiosaurus dolichodeirus. Other species once assigned to this genus, including P. brachypterygius, P. guilielmiimperatoris, and P. tournemirensis have been reassigned to new genera, such as Hydrorion, Seeleyosaurus and Microcleidus.
Elasmosaurus is a genus of plesiosaur that lived in North America during the Campanian stage of the Late Cretaceous period, at about 80.6 to 77 million years ago. The first specimen was discovered in 1867 near Fort Wallace, Kansas, US, 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 now lost pectoral and pelvic girdles, and a single species is recognized today; other species are now considered invalid or have been moved to other genera. A fragmentary elasmosaurid specimen from Germany may belong to this genus.
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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.
Muraenosaurus is an extinct genus of cryptoclidid plesiosaur reptile from the Oxford Clay of Southern England. The genus was given its name due to the eel-like appearance of the long neck and small head. Muraenosaurus grew up to 5.2 metres (17 ft) in length and lived roughly between 160 Ma and 164 Ma in the Callovian of the middle Jurassic. Charles E. Leeds collected the first Muraenosaurus which was then described by H. G. Seeley. The specimen may have suffered some damage due to the casual style of Charles Leeds’ collection. The first muraenosaur was recovered with pieces missing from the skull and many of the caudal vertebrae absent. Because the animal was described from Charles Leeds’ collection it was given the name Muraenosaurus Leedsii. M. leedsii is the most complete specimen belonging to the genus Muraenosaurus and also the only species that is undoubtedly a member of the genus. Two other species have been tentatively referred to as members of the genus Muraenosaurus: M. reedii and Muraenosaurus beloclis Seeley 1892, which in 1910 became the separate genus Picrocleidus.
Peloneustes is a genus of pliosaurid plesiosaur from the Middle Jurassic of England. Its remains are known from the Peterborough Member of the Oxford Clay Formation, which is Callovian in age. It was originally described as a species of Plesiosaurus by palaeontologist Harry Govier Seeley in 1869, before being given its own genus by naturalist Richard Lydekker in 1889. While many species have been assigned to Peloneustes, P. philarchus is currently the only one still considered valid, with the others moved to different genera, considered nomina dubia, or synonymised with P. philarchus. Some of the material formerly assigned to P. evansi have since been reassigned to "Pliosaurus" andrewsi. Peloneustes is known from many specimens, including some very complete material.
Adriosaurus is an extinct genus of squamate which lived in what is now Slovenia and other parts of Europe during the Late Cretaceous. It was a small, snake-like reptile, with the type species Adriosaurus suessi measuring up to 30 cm (12 in) in length. Adriosaurus represents the first occurrence of vestigial limbs in fossil lizards, having lost its manus and forearm completely in order to elongate its axial skeleton. These unique anatomical features led to discussions of the evolutionary patterns of limb reduction in Squamata.
Yuzhoupliosaurus is an extinct genus of plesiosaur from the Middle Jurassic of China. The genus is known only from a lower jaw, eighteen vertebrae, fragments of a pectoral girdle and parts of the right hindlimb. It is believed this genus lived in fresh water.
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Brancasaurus is a genus of plesiosaur which lived in a freshwater lake in the Early Cretaceous of what is now North Rhine-Westphalia, Germany. With a long neck possessing vertebrae bearing distinctively-shaped "shark fin"-shaped neural spines, and a relatively small and pointed head, Brancasaurus is superficially similar to Elasmosaurus, albeit smaller in size at 3.26 metres (10.7 ft) in length as a subadult.
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