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Plesiosaur

2007 Schools Wikipedia Selection. Related subjects: Dinosaurs

   iPlesiosaur

                    Fossil range: Jurassic to Cretaceous

                Scientific classification

   Kingdom:    Animalia
   Phylum:     Chordata
   Class:      Reptilia
   Superorder: Sauropterygia
   Order:      Plesiosauria
   Suborder:   Plesiosauroidea
               Gray, 1825

                                  Families

   Cimoliasauridae
   Cryptoclididae
   Elasmosauridae
   Plesiosauridae
   Polycotylidae

   Plesiosaurs ( IPA /ˈplisɪəˌsɔɹ/) ( 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". 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.

   The first plesiosaur skeletons were found in England by Mary Anning, in
   the early 1800s. A virtually complete plesiosaur skeleton was 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.

   It is occasionally claimed that plesiosaurs are not extinct, although
   the evidence for this belief is generally not accepted in the
   scientific world. The modern 'sightings' that are occasionally reported
   are usually explained either as basking shark carcasses or as hoaxes.

Description

   Cryptoclidus reconstruction in Oxford University Museum of Natural
   History
   Enlarge
   Cryptoclidus reconstruction in Oxford University Museum of Natural
   History

   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.

Behaviour

   Plesiosaur paddle in the Charmouth Heritage Coast Centre.
   Enlarge
   Plesiosaur paddle in the Charmouth Heritage Coast Centre.

   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 (they could not), gravity
   would have tipped their body forward and kept most of the heavy neck in
   the water.

Taxonomy

   The classification of plesiosaurs has varied over time; the following
   represents one current version (see O'Keefe 2001)
     * Superorder SAUROPTERYGIA
          + Order PLESIOSAURIA
               o Suborder Pliosauroidea
               o Suborder Plesiosauroidea
                    # Family Plesiosauridae
                    # (Unranked) Euplesiosauria
                         @ Family Elasmosauridae
                         @ Superfamily Cryptoclidoidea
                              - Family Cryptoclididae
                              - (Unranked) Tricleidia
                                   = Tricleidus
                                   = Family Cimoliasauridae
                                   = Family Polycotylidae

In fiction

   The plesiosaur is popular among children and cryptozoologists,
   appearing in a number of children's books and several films. It fought
   an icthyosaur in Jules Verne's novel Journey to the Centre of the
   Earth. 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). There are
   also unsubstantiated rumors across the Internet that a plesiosaur may
   be featured in the upcoming film Jurassic Park IV.

   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 a
   Megalodon 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 fuelled 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 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.

   However, these arguments have all been opposed by Robert Rines, who
   said that "animals can adapt" and that "some reptiles can stay in water
   for a long time". "Many sightings tell of "horns" or "ears", which may
   be nostrils. If it(the monster) breathes regularly, it could breathe
   without being noticed".

   While no definitive claims have been made about the biology of the
   plesiosaurs, most scientific evidence points to the fact that dinosuars
   (which were contemporaries and distant relatives of plesiosaurs) were
   warm-blooded . This should not be an indication of the thermophysiology
   of the plesiosaurs, however -- modern reptiles, which are also "distant
   relatives" of dinosaurs, are most assuredly cold-blooded.

   There are some theories of how plesiosaurs may have surfaced to breathe
   but supporters of the notion of surviving plesiosaurs say that
   plesiosaurs may have lifted only their nostrils above the surface to
   breathe. Some artist's impressions of plesiosaurs support this.

   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).

   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 but the bones were later determined to be those of a whale.

   On November 2nd, 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 it's 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.

   However, there is no evidence that the monster is of that exact species
   and over time the neck muscles could have become stronger.
   Additionally, the monster is sometimes seen as only humps and the neck
   isn't always seen.

Trivia

     * The Transformers character Magmatron turns into a Plesiosaur.
     * Plesiosaurus is one of the prehistoric creatures mentioned in Jules
       Verne's " Journey to the Centre of the Earth", in which it fights
       an Ichthyosaur in the Central Sea. See also this webpage regarding
       the early descriptions of plesiosaurs in science and literature.
     * The first elasmosaur was found in Kansas

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   with only minor checks and changes (see www.wikipedia.org for details
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