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Fossil range: Early Jurassic
P. dolichodeirus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Superorder: Sauropterygia
Order: Plesiosauria
Suborder: Plesiosauroidea
Family: Plesiosauridae
Gray, 1825
Genus: Plesiosaurus
Conybeare, 1821

Plesiosaurus (Greek: πλησιος/plesios, near to + σαυρος/sauros, lizard) was a large marine sauropterygian reptile that lived during the early part of the Jurassic Period, and is known by nearly complete skeletons from the Lias of England and Germany. It was distinguished 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.



Plesiosaurus was one of the first of the "antediluvian reptiles" to be discovered (by Mary Anning), and excited great interest in Victorian England. It was so-named ("near lizard") by William Conybeare, to indicate that it was more like a normal reptile than Ichthyosaurus, which had been found in the same rock strata just a few years previously.


Plesiosaurus with a human to scale.
Cast of Plesiosaurus guilielmiiperatoris fossil with reconstructed parts

Plesiosaurus was a fairly typical member of its order, and measured around 3 to 5 metres (10 to 16 ft) in total length. The snout was short, but the mouth was able to open very wide, and the jaws were provided with a series of conical teeth in sockets, much like those of the living gavial. The neck was long and slender, but this seems to have been rather stiff, because the vertebrae are nearly flat-ended, which indicates that it could not have been bent in the swan-fashion represented in many old restorations. The other vertebrae are similarly almost flat-ended and firmly united, and there is no sacrum. The ribs are single-headed, and in the middle of the trunk, between the supports of the paired limbs, they meet a dense plastron of abdominal ribs. The short tail was straight and tapered rapidly.

The pectoral and pelvic girdles which supported the paired limbs are greatly expanded, the pectoral arch being similar to the corresponding bones of turtles.

The limbs were elongated paddles, with five complete digits, although each consists of a very large number of phalanges. Some traces of skin discovered suggest that it was smooth, not scaly.


Plesiosaurus dolichodeirus

Plesiosaurus fed on belemnites, fish and other prey. Its U-shaped jaw and sharp teeth would have been like a fish trap. It propelled itself by the paddles, the tail being too short to be of much use. Its neck could have been used as a rudder when navigating during a chase.

It is unknown if Plesiosaurus laid eggs on land like sea turtles or give live birth in the water like sea snakes. The young might have lived in estuaries before going in the open ocean.


At one time, Plesiosaurus was a wastebasket taxon used to describe any Mesozoic plesiosaur of generally similar appearance. More recently there has been a number of revisions in sauropterygian taxonomy, and many species previously included here have been moved to other genera and families. Only two species are unambiguiously recognised.

  • Plesiosaurus dolichodeirus is the type species, known from the Lower Lias (Sinemurian) of Lyme Regis, which was about three metres long. Other plesiosaurs from the same formation measure between five to six metres in length.
  • Plesiosaurus guilelmiimperatoris is known from a large almost complete skeleton from the Upper Lias (Toarcian) of Württemberg. 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.

In popular culture

Life restoration of a pair of Plesiosaurus dolichodeirus


  • Richard Owen, Fossil Reptili of the Liassic Formations, pt iii. (Monogr. Palaeont. Soc., 1865)

External links

This article incorporates text from the Encyclopædia Britannica, Eleventh Edition, a publication now in the public domain.


1911 encyclopedia

Up to date as of January 14, 2010
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From LoveToKnow 1911

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Up to date as of January 23, 2010

From Wikispecies

Plesiosaurus dolichodeirus


Main Page
Cladus: Eukaryota
Supergroup: Unikonta
Cladus: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Reptilia
Subclassis: Diapsida
Infraclassis: Lepidosauromorpha
Superordo: †Sauropterygia
Ordo: Plesiosauria
Familia: Plesiosauridae
Genus: Plesiosaurus
Species: P. dolichodeirus - P. guilelmiimperatoris


Plesiosaurus de La Beche & Conybeare, 1821


  • Richard Owen, Fossil Reptili of the Liassic Formations, pt III. (Monogr. Palaeont. Soc., 1865)

Vernacular names

한국어: 플레시오사우루스
日本語: プレシオサウルス
Polski: Plezjozaur
中文: 蛇頸龍

Simple English

Fossil range: Lower Jurassic
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Sauropterygia
Order: Plesiosauria
Suborder: Plesiosauroidea
Family: Plesiosauridae
Gray, 1825
Genus: Plesiosaurus
Conybeare, 1821

P. dolichodirus
P. guilelmiimperatoris
? P. brachypterygius (jr. synon.?)
? P. tournemirensis (jr. synon.?)

Plesiosaurus was a large fossil marine reptile, discovered by Mary Anning in 1820-21. The one she discovered on the 'Jurassic Coast' of Lyme Regis, England, was missing its skull. In 1823 she found another one, this time complete with its skull. The name Plesiosaurus was given by the Rev. William Conybeare.

Plesiosaurus was a prehistoric marine animal. It was a predator, living mostly on fish. It would swim through schools of fish and use its long neck and sharp teeth to snap them up.

Illustration of one of Anning's finds: Plesiosaurus macrocephalus


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