From Wikipedia, the free encyclopedia

This article or section includes a list of references or external links, but its sources remain unclear because it lacks in-text citations. You can improve this article by introducing more precise citations.

Plesiosaur Fossil range: Early Jurassic - Late Cretaceous
Artist's reconstruction of Plesiosaurus.
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Superorder: Sauropterygia Order: Plesiosauria Suborder: Plesiosauroidea Gray, 1825
Families
Cimoliasauridae Cryptoclididae Elasmosauridae Plesiosauridae Polycotylidae

Plesiosaurs (pronounced /ˈpliːsɪəˌsɔr/) (Greek: plesios meaning 'near' or 'close to' and sauros meaning 'lizard') were carnivorous aquatic (mostly marine) reptiles. After their discovery, they were somewhat fancifully said to have resembled "a snake threaded through the shell of a turtle", although they had no shell. The common name 'plesiosaur' is applied both to the 'true' plesiosaurs (Suborder Plesiosauroidea) and to the larger taxonomic rank of Plesiosauria, which includes both long-necked (elasmosaurs) and short-necked (polycotylid) forms. Short-necked, large-headed plesiosaurs are more properly called pliosaurs. There were many species of plesiosaurs and not all of them were as large as Liopleurodon, Kronosaurus or Elasmosaurus.

Plesiosaurs (sensu Plesiosauroidea) first appeared at the very start of the Jurassic Period and thrived until the K-T extinction, at the end of the Cretaceous Period. While they were Mesozoic reptiles that lived at the same time as dinosaurs, they were not dinosaurs.

Contents 1 History of discovery 2 Description 3 Behaviour 4 Taxonomy 5 In popular culture 5.1 Alleged living plesiosaurs 6 See also 7 References 8 External links

The first plesiosaur skeletons were found in England by Mary Anning, in the early 1800s, and were amongst the first fossil vertebrates to be described by science. Many have been found, some of them virtually complete, and new discoveries are made frequently. One of the finest specimens was found in 2002 on the coast of Somerset (UK) by someone fishing from the shore. This specimen, called the Collard specimen after its finder, will be on display in Taunton museum in 2007. Another, less complete skeleton was also found in 2002, in the cliffs at Filey, Yorkshire, England, by an amateur palaeontologist. The preserved skeleton will be displayed at Scarborough's new Rotunda Museum, from 2007.

Many museums all over the world contain plesiosaur specimens. Notable among them is the collection of plesiosaurs in the Natural History Museum, London, which are on display in the marine reptiles gallery. Several historically important specimens can be found there, including the partial skeleton from Nottinghamshire reported by Stukely in 1719 which is the earliest written record of any marine reptile. Others specimens include those purchased from Thomas Hawkins in the early 19th century.

Historic specimens such as these are on display in several museums in the UK, including New Walk Museum, Leicester, The Yorkshire Museum, The Sedgwick Museum in Cambridge, Manchester Museum, Warwick Museum, Bristol Museum and the Dorset Museum. A historic specimen which has recently been prepared as part of a scientific study was put on display in Lincoln Museum in 2005. Peterborough Museum holds an excellent collection of plesiosaur material from the Oxford Clay brick pits in the surrounding area, most of which has been collected relatively recently. The most complete known specimen of the long-necked plesiosaur Cryptoclidus, excavated in the 1980s can be seen there.

Typical plesiosaurs had a broad body and a short tail. They retained their ancestral two pairs of limbs, which evolved into large flippers. Plesiosaurs evolved from earlier, similar forms such as pistosaurs or very early, longer-necked pliosaurs. There are a number of families of plesiosaurs, which retain the same general appearance and are distinguished by various specific details. These include the Plesiosauridae, unspecialised types which are limited to the Early Jurassic period; Cryptoclididae, (e.g. Cryptoclidus), with a medium-long neck and somewhat stocky build; Elasmosauridae, with very long, inflexible necks and tiny heads; and the Cimoliasauridae, a poorly known group of small Cretaceous forms. According to traditional classifications, all plesiosaurs have a small head and long neck but, in recent classifications, one short-necked and large-headed Cretaceous group, the Polycotylidae, are included under the Plesiosauroidea, rather than under the traditional Pliosauroidea.

Unlike their Pliosaurian cousins, Plesiosaurs (with the exception of the Polycotylidae) were probably relatively slow swimmers. It is likely that they cruised slowly below the surface of the water, using their long flexible neck to move their head into position to snap up unwary fish or cephalopods. Their unique, four-flippered swimming adaptation may have given them exceptional maneuverability, so that they could swiftly rotate their bodies as an aid to catching their prey.

Contrary to many reconstructions of plesiosaurs, it would have been impossible for them to lift their head and long neck above the surface, in the 'swan-like' pose that is often shown. Even if they had been able to bend their necks upward to that degree (which they could not), gravity would have tipped their body forward and kept most of the heavy neck in the water.

The classification of plesiosaurs has varied over time; the following represents one current version (see O'Keefe 2001)

• Superorder SAUROPTERYGIA
  • Order PLESIOSAURIA
    • Suborder Pliosauroidea
    • Suborder Plesiosauroidea(Gray, 1825) Welles, 1943 sensu O'Keefe, 2001
      • Plesiopterys O'Keefe, 2004
      • Family Plesiosauridae Gray, 1825 sensu O'Keefe, 2001
        • Attenborosaurus Bakker, 1993
        • Plesiosaurus De la Beche & Conybeare, 1821
      • (Unranked) Euplesiosauria O'Keefe, 2001
        •  ? Sthenarosaurus Watson, 1911 (nomen dubium)
        •  ? Eretmosaurus Seeley, 1874
        •  ? Leurospondylus Brown, 1913
        • Superfamily Cryptoclidoidea Williston, 1925 sensu O'Keefe, 2001
          • Family Cryptoclididae Williston, 1925 sensu O'Keefe, 2001
            •  ? Tatenectes O’Keefe & Wahl, 2003
            •  ? Colymbosaurus Seeley, 1874
            • Cryptocleidus Seeley, 1892
            • Muraenosaurus Seeley, 1874
            • Pantosaurus Marsh, 1891
            • Vinialesaurus Gasparini, Bardet & Iturralde-Vinent, 2002
          • (Unranked) Tricleidia O'Keefe, 2001
            • Family Tricledidae Nova
              • Tricleidus Andrews, 1909
            • Family Cimoliasauridae Delair, 1959 sensu O'Keefe, 2001
              •  ? Aristonectes Cabrea, 1941
              • Kaiwhekea Cruickshank & Fordyce, 2002
              • Kimmerosaurus Brown, 1981
              • Cimoliasaurus Leidy, 1851 (nomen dubium)
            • Family Polycotylidae Williston, 1909 sensu O'Keefe, 2001
              •  ? Edgarosaurus Druckenmiller, 2002
              •  ? Georgiasaurus Otschev, 1978
              • Polycotylus Cope, 1869
              • Dolichorhynchops Willison, 1903
              • Trinacromerum Cragin, 1888
              • Sulcusuchus Gasparini & Spalletti, 1990
              • Thililua Bardet, Pereda Suberbiola & Jalil, 2003
            • Family Elasmosauridae Cope, 1869 sensu Bardet, Godefroit & Sciau, 1999
              •  ? Morenosaurus Welles, 1943
              • Occitanosaurus Bardet, Godefroit & Sciau, 1999
              • Microcleidus Watson, 1911
            • Family Elasmosauridae Cope, 1869 sensu O'Keefe, 2001
              •  ? Futabasaurus Sato, Hasegawa & Manabe, 2006
              •  ? Orophosaurus Cope, 1887 (nomen dubium)
              •  ? Woolungasaurus Persson, 1960
              •  ? Ogmodirus Williston & Moodie, 1913 (nomen dubium)
              •  ? Fresnosaurus Welles, 1943
              •  ? Piptomerus Cope, 1887 (nomen vanum)
              •  ? Goniosaurus Meyer, 1860
              •  ? Mauisaurus Hector, 1874
              •  ? Aphrosaurus Welles, 1943
              •  ? Hydrotherosaurus Welles, 1943
              •  ? Hydralmosaurus Welles, 1943
              •  ? Terminonatator Sato, 2003
              •  ? Turangisaurus Wiffen & Moisley, 1986
              •  ? Thalassomedon Welles, 1943
              • Elasmosaurus Cope, 1869
              • Brancasaurus Wegner, 1914
              • Callawayasaurus Carpenter, 1999
              • Libonectes Carpenter, 1997
              • Styxosaurus Welles, 1943

The plesiosaur is popular among children and cryptozoologists, appearing in a number of children's books and several films, including an icthyosaur in Jules Verne's novel Journey to the Center of the Earth. However, in Verne's story it is described as being much larger than it was in reality, and shown as having a shell like a turtle. In the bizarre 1899 short story "The Monster of Lake LaMetrie", a man's brain was put into the body of a plesiosaur.

It has appeared in films about lake monsters, including Magic in the Water (1995), and movies about the Loch Ness Monster, such as Loch Ness (1996). In both films, the creature primarily serves as a symbol of a lost, child-like sense of wonder. The plesiosaur is also present in the Japanese Jaws-inspired movie Legend of the Dinosaurs (1983).

Contrary to reports, the long-necked, sharp-toothed creature in the classic film King Kong (1933), which flips a raft full of rescuers on their way to save Fay Wray and then munches on the swimmers, is not a plesiosaur. Despite striking a profile in the mist very similar to the famous 'Surgeon's Photo' of the Loch Ness Monster, it then chases the routed heroes onto dry land, where it is clearly intended to be a sauropod, like Brontosaurus (now Apatosaurus). However, Kong later battles a serpent-like creature in a cave, which possesses four flippers and resembles a plesiosaur but acts more like some kind of giant snake. But it has been rumored to be a Tanystropheus, a long necked prehistoric reptile which swam in the ocean, catching fish, much like plesiosaurs.

In Steve Alten's novel The Trench, a climatic scene at the end has a Megalodon fighting with several deep sea reptiles, similar to Pliosaurs, identified as Kronosaurs.

This article does not cite any references or sources. (February 2007) Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed.

Main articles: sea monster, lake monster, and Loch Ness Monster

Lake or sea monster sightings are occasionally explained by cryptozoologists as plesiosaurs^{[citation needed]}. While the survival of a small, unrecorded breeding colony of plesiosaurs for the 65,000,000 years since their apparent extinction is highly unlikely, the discovery of real and even more ancient living fossils such as the Coelacanth and of previously unknown but enormous deep-sea animals such as the giant squid, have fueled imaginations.

The 1977 discovery of a carcass with flippers and what appeared to be a long neck and head, by the Japanese fishing trawler Zuiyo Maru, off New Zealand, created a plesiosaur craze in Japan. Members of a blue-ribbon panel of eminent marine scientists in Japan reviewed the discovery. Professor Yoshinori Imaizumi, of the National Science Museum of Japan, said, "It's not a fish, whale, or any other mammal." However, the general consensus amongst scientists today is that it was a decayed basking shark. The long neck described may be attributed to the loss of the lower jaw (a favorite of scavengers).[1]

The Loch Ness Monster has been reported to resemble a plesiosaur. Arguments against the plesiosaur theory include the fact that the lake is too cold for a cold-blooded animal to survive easily, that air-breathing animals like plesiosaurs would be easily spotted when they surface to breathe, that the lake is too small to support a breeding colony and that the loch itself formed only 10,000 years ago during the last ice age.

The National Museums of Scotland confirmed that vertebrae discovered on the shores of Loch Ness, in 2003, belong to a plesiosaur, although there are some questions about whether the fossils were planted (BBC News, July 16, 2003).

Beached carcasses that prove controversial or hard to identify, a phenomenon known as globsters, have fueled the debate about living plesiosaurs. It was reported in The Star (Malaysia) on April 8, 2006, that fishermen discovered bones resembling that of a Plesiosaur near Sabah, Malaysia. The creature was speculated to have died only a month before. A team of researchers from Universiti Malaysia Sabah investigated the specimen but the bones were later determined to be those of a whale.

On November 2, 2006, Leslie Noè of the Sedgwick Museum in Cambridge, UK, announced research which casts further doubt on a plesiosaur inhabiting Loch Ness. While many sightings of the monster include reports of it lifting its head out of the water, including the Spurling photo, Noè's study of fossilized vertebrae of a Muraenosaurus concluded this articulation would not be possible. Instead, he found that the neck evolved to point downwards allowing the plesiosaur to feed on soft-shelled animals living on the sea floor. [2]

Another creature closely resembling a plesiosaur has been reported to exist in Lake Khaiyr in Eastern Siberia. However, due to the extreme remoteness of the location and the fear of volcanic activity, the lake is rarely visited by scientists or tourists and consequently there have been few sightings.

• Australian plesiosaurs

See also Mike Everhart's "Marine Reptile References" and scans of "Early papers on North American plesiosaurs" on the Oceans of Kansas Paleontology website.

• Fox News: Possibly Complete Plesiosaur Skeleton Found in Arctic
• The Plesiosaur Site. Richard Forrest.
• The Plesiosaur Directory. Adam Stuart Smith.
• Plesiosaur FAQ's. Raymond Thaddeus C. Ancog.
• Oceans of Kansas Paleontology. Mike Everhart.
• Where the elasmosaurs roam: Separating fact from fiction. Mike Everhart.
• The history of the description of a plesiosaur as a "snake drawn through the shell of a turtle. Mike Everhart and other contributors.
• "Plesiosaur fossil found in Bridgwater Bay". Somersert Museums County Service. (best known fossil)
• "Fossil hunters turn up 50-ton monster of prehistoric deep". Allan Hall and Mark Henderson. Times Online, December 30, 2002. (Monster of Aramberri)
• "A Jurassic fossil discovered in Loch Ness by a Scots pensioner could be the original Loch Ness monster, according to Nessie enthusiasts". BBC News, July 16, 2003. (Loch Ness, possible hoax)
• "Sea-monster or shark? an analysis of a supposed plesiosaur carcass netted in 1977". Glen J. Kuban.
• "A Plesiosaur? Here is the other side of the story. It looks like one to me.". Internet reference to article.
• Triassic reptiles had live young.
• Bridgwater Bay juvenile plesiosaur
• The Filey (Yorkshire) Plesiosaur 2002 (part 1)
• The Filey (Yorkshire) Plesiosaur 2002 (part 2)
• - Plesiosaur in Nebraska - NET Television
• Antarctic Researchers to Discuss Difficult Recovery of Unique Juvenile Plesiosaur Fossil, from the National Science Foundation, December 6, 2006.