Plesiosaur
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{{Taxobox
| color = pink
| name = Plesiosaur
| status = Conservation status: Fossil
| image = Plesiosaur-illustration.png
| regnum = Animalia
| phylum = Chordata
| classis = Reptilia
| superordo = Sauropterygia
| ordo = Plesiosauria
| ordo_authority = de Blainville, 1835
| subdivision_ranks = Families
| subdivision =
Cryptoclididae
Elasmosauridae
Plesiosauridae
Pliosauridae
}}
Plesiosaurs (IPA Template: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.
They first appeared in the late Triassic 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.
Contents |
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 the earlier nothosaurs, who had a more crocodile-like body; major types of plesiosaur are primarily distinguished by head and neck size.
As a group, the plesiosaurs were the largest aquatic animals of their time, and even the smallest were about 2 m (6.5 ft) long. They grew to be considerably larger than the largest giant crocodiles, and were bigger than their successors, the mosasaurs. However, their predecessors as rulers of the sea, the dolphin-like ichthyosaurs, are known to have reached 23 m in length, and the modern whale shark (18 m), sperm whale (20 m), and especially the blue whale (30 m) are known from considerably larger specimens.
The anteriorly placed internal nostrils have palatal grooves to channel water, the flow of which would be maintained by hydrodynamic pressure over the posteriorly placed external nares during locomotion. During its passage through the nasal ducts, the water would have been 'tasted' by olfactory epithelia.
Mary Anning (1799 - 1847) was famous for her Plesiosaur discoveries at Lyme Regis in Dorset, UK. She is credited with the first Plesiosaur find (Plesiosaurus dolichodeirus), which has become the 'type fossil' (genoholotype). This region of Britain is now a World Heritage Site, dubbed the Jurassic Coast.
Behaviour
Plesiosaurs have been discovered with fossils of belemnites (squid-like animals), and ammonites (giant nautilus-like molluscs) associated with their stomachs. They had powerful jaws, probably strong enough to bite through the hard shells of their prey. The bony fish (Osteichthyes), started to spread in the Jurassic, and were likely prey as well. Recent evidence seems to indicate that some plesiosaurs may have, in fact, been bottom feeders.[1]
It has been theorized that smaller plesiosaurs may have crawled up on a beach to lay their eggs, like the modern leatherback turtle, but it is now clear plesiosaurs gave birth to live young.
Another curiosity is their four-flippered design. No modern animals have this swimming adaptation, so there is considerable speculation about what kind of stroke they used. While the short-necked pliosaurs may have been fast swimmers, the long-necked varieties were built more for maneuverability than for speed. Skeletons have also been discovered with gastroliths in their stomachs, probably to help with buoyancy.
Recent discoveries
In 2002, the "Monster of Aramberri" was announced to the press. Discovered in 1982 at the village of Aramberri, in the Mexican state of Nuevo León, it was originally classified as a dinosaur. The specimen is actually a very large plesiosaur, possibly reaching 15 m (50 ft) in length. The media published exaggerated reports claiming it was 25 m (80 ft) long, and weighed up to 150,000 kg, which made it the largest predator of all time. This error was perpetuated in BBC's documentary series Walking with Dinosaurs, which also prematurely classified it as a Liopleurodon ferox.
In 2004, what appears to be a 100 percent intact juvenile plesiosaur was discovered at Bridgwater Bay National Nature Reserve in the United Kingdom, by a local fisherman. The fossil measures 1.5 m (5 ft) in length, and may be related to the Rhomaleosaurus. It is probably the best preserved specimen of a plesiosaur ever
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.
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 posesses 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
Main articles: sea monster, lake monster, Loch Ness Monster
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 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." [2]
The Loch Ness Monster is sometimes reported to resemble a plesiosaur, but just as frequently bears little or no resemblance to one. 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. Template:Fact
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 had died only a month before. A team of researchers from Universiti Malaysia Sabah was currently investigating the specimen. However, the bones were later determined to be that of a whale.
Plesiosaurus is one of the Pre-historic creatures mentioned in Jules Verne's "Journey to the Center of the Earth" were it fights an Ichthyosaur in the Central Sea.
Trivia
- The Transformers character Magmatron turns into a Plesiosaur.
External links
- The Plesiosaur Site. Richard Forrest.
- The Plesiosaur Directory. Adam Stuart Smith.
- Plesiosaur FAQ's. Raymond Thaddeus C. Ancog.
- Oceans of Kansas Paleontology. Mike Everhart.
- "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.
- Plesiosaur or Basking Shark? You decide.. Creationist research on the issue.
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, R., 2001: 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.bg:Плезиозаври
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