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Pliosauroidea

Extinct clade of reptiles

Summary

Extinct clade of reptiles

Pliosauroidea is an extinct clade of plesiosaurs, known from the latest Triassic to early Late Cretaceous. They are best known for the subclade Thalassophonea, which contained crocodile-like short-necked forms with large heads and massive toothed jaws, commonly known as pliosaurs. More primitive non-thalassophonean pliosauroids resembled plesiosaurs in possessing relatively long necks and smaller heads. They originally included only members of the family Pliosauridae, of the order Plesiosauria, but several other genera and families are now also included, the number and details of which vary according to the classification used.

The distinguishing characteristics are a short neck and an elongated head, with larger hind flippers compared to the fore flippers, the opposite of the plesiosaurs. They were carnivorous and their long and powerful jaws carried many sharp, conical teeth. Pliosaurs range from 4 to 10 meters or more in length. Their prey may have included fish, sharks, ichthyosaurs, dinosaurs and other plesiosaurs.

The largest known species are Kronosaurus and Pliosaurus macromerus; other well known genera include Rhomaleosaurus, Peloneustes, and Macroplata. Fossil specimens have been found in Africa, Australia, China, Europe, North America and South America.

Many very early (from the Early Jurassic and possibly Latest Triassic, i.e. Rhaetian) primitive pliosauroids were very like plesiosauroids in appearance and, indeed, used to be included in the family Plesiosauridae.

Name

Pliosauroidea was named by Welles in 1943. It is adapted from the name of the genus Pliosaurus, which is derived from the Greek πλειων (grc), meaning "more/closely", and σαυρος (grc) meaning "lizard"; it therefore means "more saurian". The name Pliosaurus was coined in 1841 by Richard Owen, who believed that it represented a link between plesiosauroids and crocodilians (considered a type of "saurian"), particularly due to their crocodile-like teeth.

Classification

Taxonomy

The taxonomy presented here is mainly based on the plesiosaur cladistic analysis proposed by Hilary F. Ketchum and Roger B. J. Benson, 2011 unless otherwise noted.

Suborder Pliosauroidea
- Eurysaurus?
- Sinopliosaurus?
- Family Rhomaleosauridae
  - Archaeonectrus
  - Bishanopliosaurus?
  - Borealonectes
  - Eurycleidus
  - Macroplata
  - Maresaurus
  - Meyerasaurus
  - Rhomaleosaurus
  - Sthenarosaurus
  - Yuzhoupliosaurus?
- Family Pliosauridae
  - Anguanax
  - Attenborosaurus
  - Eardasaurus
  - Gallardosaurus
  - Hauffiosaurus
  - Liopleurodon
  - Marmornectes
  - Megalneusaurus
  - Pachycostasaurus
  - Peloneustes
  - Pliosaurus
  - Rhaeticosaurus
  - Simolestes
  - Thalassiodracon
  - Subfamily Brachaucheninae
    - Brachauchenius
    - Kronosaurus
    - Luskhan
    - Makhaira
    - Megacephalosaurus
    - Monquirasaurus
    - Polyptychodon
    - Sachicasaurus
    - Stenorhynchosaurus

Phylogeny

Cast of ''"Plesiosaurus" macrocephalus'' found by Mary Anning, [[Muséum national d'histoire naturelle]], Paris

Pliosauroidea is a stem-based taxon that was defined by Welles as "all taxa more closely related to Pliosaurus brachydeirus than to Plesiosaurus dolichodeirus". Pliosauridae and Rhomaleosauridae are stem-based taxa too. Pliosauridae is defined as "all taxa more closely related to Pliosaurus brachydeirus than to Leptocleidus superstes, Polycotylus latipinnis or Meyerasaurus victor". Rhomaleosauridae is defined as "all taxa more closely related to Meyerasaurus victor than to Leptocleidus superstes, Pliosaurus brachydeirus or Polycotylus latipinnis". The cladogram below follows a 2011 analysis by paleontologists Hilary F. Ketchum and Roger B. J. Benson, and reduced to genera only.

Large pliosauroids

In 2002, the discovery of a very large pliosauroid was announced in Mexico. This pliosauroid came to be known as the "Monster of Aramberri". Although widely reported as such, it does not belong to the genus Liopleurodon. The remains of this animal, consisting of a partial vertebral column, were dated to the Kimmeridgian of the La Caja Formation. The fossils were found much earlier, in 1985, by a geology student and were at first erroneously attributed to a theropod dinosaur by Hahnel.Hahnel W. (1988) "Hallazgo de restos de dinosaurio en Aramberri, N.L., Mexico", Actas Fac. Cienc. Tierra UANL Linares, 3, 245–250. The remains originally contained part of a rostrum with teeth (now lost).

In August 2006, palaeontologists of the University of Oslo discovered the first remains of a pliosaur on Norwegian soil. The remains were described as "very well preserved, as well as being unique in their completeness". The large animal was determined to be a new species of Pliosaurus. The excavation of the find is documented in the 2009 History television special Predator X.

On 26 October 2009, palaeontologists reported the discovery of potentially the largest pliosauroid yet found. Found in cliffs near Weymouth, Dorset, on Britain's Jurassic Coast, the fossil had a skull length of 6 ft. Palaeontologist Richard Forrest told the BBC: "I had heard rumours that something big was turning up. But seeing this thing in the flesh, so to speak, is just jaw dropping. It is simply enormous." It was determined that the specimen belonged to a new species that scientists named Pliosaurus kevani.

In December 2023, the recent discovery of a pliosaur skull on the Dorset coast was described as "one of the most complete specimens of its type ever discovered". The discovery and research of the skull was covered in the PBS documentary Attenborough and the Jurassic Sea Monster hosted by David Attenborough.

References

[http://www.zoomdinosaurs.com/subjects/dinosaurs/glossary/indexp3.shtml#Pliosaur zoom dinosaurs]
[http://news.bbc.co.uk/2/hi/science/nature/7264856.stm Sea reptile is biggest on record]. BBC News, February 27, 2008.
(2012-12-02 }} [http://www.geologi.no/data/f/0/21/02/6_2401_0/NJG_2_3_2012_13_Knutsen_etal_Pr.pdf High resolusion pdf]{{dead link). "A new species of Pliosaurus (Sauropterygia: Plesiosauria) from the Middle Volgian of central Spitsbergen, Norway". Norwegian Journal of Geology.
Hilary F. Ketchum and Roger B. J. Benson. (2011). "A new pliosaurid (Sauropterygia, Plesiosauria) from the Oxford Clay Formation (Middle Jurassic, Callovian) of England: evidence for a gracile, longirostrine grade of Early-Middle Jurassic pliosaurids". Special Papers in Palaeontology.
Sato, Tamaki. (2008). "A new Jurassic pliosaur from Melville Island, Canadian Arctic Archipelago". Canadian Journal of Earth Sciences.
Adam S. Smith and Gareth J. Dyke. (2008). "The skull of the giant predatory pliosaur ''Rhomaleosaurus cramptoni'': implications for plesiosaur phylogenetics". Naturwissenschaften.
Gasparini, Zulma. (2009). "A New Oxfordian Pliosaurid (Plesiosauria, Pliosauridae) in the Caribbean Seaway". Palaeontology.
(2010). "Global interrelationships of Plesiosauria (Reptilia, Sauropterygia) and the pivotal role of taxon sampling in determining the outcome of phylogenetic analyses". Biological Reviews of the Cambridge Philosophical Society.
(2013). "A new Cretaceous Pliosaurid (Reptilia, Plesiosauria) from the Carlile Shale (middle Turonian) of Russell County, Kansas". Journal of Vertebrate Paleontology.
"The Plesiosaur Site - Liopleurodon".
M.-C. Buchy, E. Frey, W. Stinnesbeck, J.-G. Lopez-Oliva (2003) "First occurrence of a gigantic pliosaurid plesiosaur in the late Jurassic (Kimmeridgian) of Mexico", Bull. Soc. geol. Fr., 174(3), pp. 271–278
In the summer of 2008, the fossil remains of the huge pliosaur were dug up from the permafrost on [[Svalbard]], a Norwegian island close to the [[North Pole]].[https://web.archive.org/web/20090319022055/http://www.foxnews.com/story/0,2933,509484,00.html?sPage=fnc/scitech/evolution Fox News: Predator X Was Most Fearsome Animal to Swim Oceans]
Morelle, Rebecca. (27 October 2009). "Colossal 'sea monster' unearthed". BBC News.
Benson, Roger J. B.. (2013-05-13). "A Giant Pliosaurid Skull from the Late Jurassic of England". PLOS ONE.
(2023-12-10). "Pliosaur discovery: Huge sea monster emerges from Dorset cliffs". BBC News.
(24 January 2024). "Attenborough and the Jurassic Sea Monster". [[PBS]].

Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

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