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News: Underwater caves off Yucatan yield three old skeletons—remains date to 11,000 B.C.
http://www.edgarcayce.org/am/11,000b.c.yucata.html
 
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Plesiosaur

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Author Topic: Plesiosaur  (Read 3469 times)
Melody Stacker
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« on: October 09, 2007, 11:10:51 am »



Scientific classification
Kingdom: Animalia
 
Phylum: Chordata
 
Class: Sauropsida
 
Superorder: Sauropterygia
 
Order: Plesiosauria
 
Suborder: Plesiosauroidea
Gray, 1825
 
Families
Cimoliasauridae
Cryptoclididae
Elasmosauridae
Plesiosauridae
Polycotylidae

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Melody Stacker
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« Reply #1 on: October 09, 2007, 11:11:25 am »

Plesiosaurs (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.

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Melody Stacker
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« Reply #2 on: October 09, 2007, 11:13:30 am »



The first plesiosaur fossil, discovered by Mary Anning, 1821.
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Melody Stacker
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« Reply #3 on: October 09, 2007, 11:14:07 am »

History of discovery

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.

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Melody Stacker
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« Reply #4 on: October 09, 2007, 11:15:32 am »



Cryptoclidus reconstruction in Oxford University Museum of Natural History
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Melody Stacker
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« Reply #5 on: October 09, 2007, 11:16:32 am »

Description

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.

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Melody Stacker
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« Reply #6 on: October 09, 2007, 11:17:17 am »




Plesiosaur paddle in the Charmouth Heritage Coast Centre.
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Melody Stacker
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« Reply #7 on: October 09, 2007, 11:17:51 am »

Behaviour

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.

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Melody Stacker
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« Reply #8 on: October 09, 2007, 11:20:09 am »

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


•   Superorder SAUROPTERYGIA
o   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


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Melody Stacker
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« Reply #9 on: October 09, 2007, 11:21:07 am »



Attenborosaurus
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« Reply #10 on: October 09, 2007, 11:22:39 am »



Cryptocleidus
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Melody Stacker
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« Reply #11 on: October 09, 2007, 11:23:51 am »



Muraenosaurus
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Melody Stacker
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« Reply #12 on: October 09, 2007, 09:04:11 pm »



Dolichorhynchops
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Melody Stacker
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« Reply #13 on: October 09, 2007, 09:06:41 pm »



Thililua
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Melody Stacker
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« Reply #14 on: October 09, 2007, 09:07:50 pm »



Thalassomedon
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