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Plesiosaurs (IPA ) (Greek: plesios, near to + sauros, lizard) were large, carnivorous aquatic reptiles. They are somewhat fancifully said to have resembled "a turtle with a snake threaded through its body", though they lacked a shell. The name "Plesiosaur" is applied both to the "true" plesiosaurs (Suborder Plesiosauroidea) and to the larger taxonomic rank of Plesiosauria, which includes both long-necked and short-necked forms. Short necked Plesiosaurs are more properly called pliosaurs.

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. Despite being large Mesozoic reptiles, they were not a type of dinosaur.

It is occasionally claimed that plesiosaurs are not extinct, although the scientific evidence for this belief is disputed; the modern sightings that are occasionally reported are usually explained as basking shark carcasses or hoaxes.

Description

The typical plesiosaur 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 plesiosaur, which retain the 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 flexible 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.

Behaviour

Unlike their Pliosaurian cousins, Plesiosaurs (with the exception of the Polycotylidae) were probably slow swimmers and not very streamlined. It is thought that they cruised slowly near the surface of the water, darting their head to snap up unwary fish or cephalopods, using their long flexible neck. Their unique, four-flippered swimming adaptation may have given them exceptional maneouvurability, so that they could swiftly rotate their bodies as an aid to catching their prey.

Taxonomy

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

In fiction

The plesiosaur is popular among children and cryptozoologists, and appears in a number of children's books, and several films. 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 the 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. In Steve Alten's novel The Trench, a climatic scene at the end has Angel fighting with several deep sea reptiles similar to Pliosaurs - identified as Kronosaurs.

Alleged living plesiosaurs

Lake or sea monster sightings are occasionally explained as plesiosaurs. While the survival of a small, unrecorded breeding colony of plesiosaurs for the 65,000,000 years (with respect to evolution) since their apparent extinction is 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 Japanese National Science Museum said, "It's not a fish, whale, or any other mammal." Others argued that it was actually a decayed basking shark, but Professor Toshio Kasuya said, "If it were a shark, the spine would be smaller, and the neck itself is too long as shown in the picture. I think we can exclude the fish theory." *

The Loch Ness Monster is 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 easily survive, 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, though there are some questions about whether the fossils were planted (BBC News, July 16, 2003).

It was reported in The Star (Malaysia) on April 8th, 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. However, the bones were later determined to be that of a whale.

Trivia

External links

References

  • Lingham-Soliar, T., 1995: in Phil. Trans. Roy. Soc. Lond. 347: 155-180
  • Cicimurri, D., and M. Everhart, 2001: in Trans. Kansas. Acad. Sci. 104: 129-143
  • O'Keefe, F. R., 2001: A cladistic analysis and taxonomic revision of the Plesiosauria (Reptilia: Sauropterygia); Acta Zool. Fennica 213: 1-63
  • White, T., 1935: in Occasional Papers Boston Soc. Nat. Hist. 8: 219-228
  • Hampe, O., 1992: Courier Forsch.-Inst. Senckenberg 145: 1-32
  • Ellis, R. 2003: Sea Dragons' (Kansas University Press)
  • ( ), 1997: in Reports of the National Center for Science Education, 17.3 (May/June 1997) pp 16–28.
  • Everhart, M.J. 2005. "Where the Elasmosaurs roamed," Chapter 7 in "Oceans of Kansas: A Natural History of the Western Interior Sea," Indiana University Press, Bloomington, 322 p.
  • Everhart, M.J. 2005. "Gastroliths associated with plesiosaur remains in the Sharon Springs Member (Late Cretaceous) of the Pierre Shale, Western Kansas" (on-line, updated from article in Kansas Acad. Sci. Trans. 103(1-2):58-69)

Sauropterygia

Plesiosaor | Плезиозаври | Plesiosaure | Plesiosaurus | Plesiosaurier | Plesiosauria | Plésiosaure | Plesiosaurus | Plesiosauria | פלסיוזאוריה | Plesiosauria | プレシオサウルス | Svaneøgler | Plezjozaury | Plesiossauro | Plesiosaurier

 

This article is licensed under the GNU Free Documentation License. It uses material from the "Plesiosaur".

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