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Pliosauroidea is an
extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English ter ...
of plesiosaurs, known from the earliest
Jurassic The Jurassic ( ) is a geologic period and stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately Mya. The Jurassic constitutes the middle period of ...
to early Late
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
. They are best known for the subclade
Thalassophonea Thalassophonea is an extinct clade of pliosaurids from the Middle Jurassic to the early Late Cretaceous ( Callovian to Turonian) of Australia, Europe, North America and South America. ''Thalassophonea'' was erected by Roger Benson and Patrick ...
, which contained
crocodile Crocodiles (family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to include all extant me ...
-like short-necked forms with large heads and massive toothed jaws, commonly known as pliosaurs. More primitive non-thalassophonean pliosauroids resembled pleisiosaurs in possessing relatively long necks and smaller heads. They originally included only members of the family Pliosauridae, of the order
Plesiosauria The Plesiosauria (; Greek: πλησίος, ''plesios'', meaning "near to" and ''sauros'', meaning "lizard") or plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared ...
, 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 Flipper may refer to: Common meanings *Flipper (anatomy), a forelimb of an aquatic animal, useful for steering and/or propulsion in water *Alternate name for a swimfin, footwear that boosts human swimming efficiency * Flipper (cricket), a type of ...
compared to the fore flippers, the opposite of the plesiosaurs. They were
carnivorous A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...
and their long and powerful jaws carried many sharp, conical teeth. Pliosaurs range from 4 to 15 metres and more in length. Their prey may have included
fish Fish are Aquatic animal, aquatic, craniate, gill-bearing animals that lack Limb (anatomy), limbs with Digit (anatomy), digits. Included in this definition are the living hagfish, lampreys, and Chondrichthyes, cartilaginous and bony fish as we ...
, sharks,
ichthyosaur Ichthyosaurs (Ancient Greek for "fish lizard" – and ) are large extinct marine reptiles. Ichthyosaurs belong to the order known as Ichthyosauria or Ichthyopterygia ('fish flippers' – a designation introduced by Sir Richard Owen in 1842, alt ...
s,
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s and other plesiosaurs. The largest known species are ''
Kronosaurus ''Kronosaurus'' ( ; meaning "lizard of Kronos") is a potentially dubious genus of extinct short-necked pliosaur. With an estimated length of , it was among the largest pliosaurs, and is named after the leader of the Greek Titans, Kronos. It ...
'' and '' Pliosaurus macromerus''; other well known genera include ''
Rhomaleosaurus ''Rhomaleosaurus'' (meaning "strong lizard") is an extinct genus of Early Jurassic (Toarcian age, about 183 to 175.6 million years ago) rhomaleosaurid pliosauroid known from Northamptonshire and from Yorkshire of the United Kingdom. It was ...
'', '' Peloneustes'', and '' Macroplata''.Low resolusion pdfHigh resolusion pdf
/ref> Fossil specimens have been found in
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,
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
,
China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...
,
Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
,
North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
and
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
. Many very early (from the
Early Jurassic The Early Jurassic Epoch (geology), Epoch (in chronostratigraphy corresponding to the Lower Jurassic series (stratigraphy), Series) is the earliest of three epochs of the Jurassic Period. The Early Jurassic starts immediately after the Triassic-J ...
and possibly Latest
Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...
, i.e.
Rhaetian The Rhaetian is the latest age of the Triassic Period (in geochronology) or the uppermost stage of the Triassic System (in chronostratigraphy). It was preceded by the Norian and succeeded by the Hettangian (the lowermost stage or earliest a ...
) primitive pliosauroids were very like plesiosauroids in appearance and, indeed, used to be included in the family
Plesiosauridae The Plesiosauridae are a monophyletic group of plesiosaurs.Ketchum, H. F., and Benson, R. B. J., 2010. "Global interrelationships of Plesiosauria (Reptilia, Sauropterygia) and the pivotal role of taxon sampling in determining the outcome of phylo ...
.


Name

Pliosauroidea was named by Welles in 1943. It is adapted from the name of the genus ''
Pliosaurus ''Pliosaurus'' (meaning 'more lizard') is an extinct genus of thalassophonean pliosaurid known from the Kimmeridgian and Tithonian stages (Late Jurassic) of Europe and South America. Their diet would have included fish, cephalopods, and marine ...
'', which is derived from the
Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...
(), meaning "more/closely", and () meaning "lizard"; it therefore means "more saurian". The name ''Pliosaurus'' was coined in 1841 by
Richard Owen Sir Richard Owen (20 July 1804 – 18 December 1892) was an English biologist, comparative anatomist and paleontologist. Owen is generally considered to have been an outstanding naturalist with a remarkable gift for interpreting fossils. Ow ...
, who believed that it represented a link between plesiosauroids and
crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period (Cenomanian stage) and are the closest livin ...
s (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 Rhomaleosauridae is a family of plesiosaurs from the Earliest Jurassic to the latest Middle Jurassic (Hettangian to Callovian stages) of Europe, North America, South America and possibly Asia. Most rhomaleosaurids are known from England, many ...
*** '' Archaeonectrus'' *** '' Borealonectes'' ***? '' Bishanopliosaurus'' *** '' Eurycleidus'' *** '' Macroplata'' *** '' Maresaurus'' *** ''
Rhomaleosaurus ''Rhomaleosaurus'' (meaning "strong lizard") is an extinct genus of Early Jurassic (Toarcian age, about 183 to 175.6 million years ago) rhomaleosaurid pliosauroid known from Northamptonshire and from Yorkshire of the United Kingdom. It was ...
'' *** '' Meyerasaurus'' *** '' Sthenarosaurus'' ***? '' Yuzhoupliosaurus'' **Family Pliosauridae *** '' Anguanax'' *** '' Attenborosaurus'' *** '' Gallardosaurus'' *** '' Hauffiosaurus'' *** '' Marmornectes'' *** '' Megalneusaurus'' *** ''
Liopleurodon ''Liopleurodon'' (; meaning 'smooth-sided teeth') is an extinct genus of large, carnivorous marine reptile belonging to the Thalassophonea, a clade of short-necked pliosaurid plesiosaurs. ''Liopleurodon'' lived from the Callovian Stage of the M ...
'' *** '' Eardasaurus'' *** '' Pachycostasaurus'' *** '' Peloneustes'' *** ''
Pliosaurus ''Pliosaurus'' (meaning 'more lizard') is an extinct genus of thalassophonean pliosaurid known from the Kimmeridgian and Tithonian stages (Late Jurassic) of Europe and South America. Their diet would have included fish, cephalopods, and marine ...
'' *** '' Rhaeticosaurus'' *** ''
Simolestes ''Simolestes'' (meaning "hearkening thief") is an extinct pliosaurid genus that lived in the Middle to Late Jurassic. The type specimen, BMNH R. 3319 is an almost complete but crushed skeleton diagnostic to ''Simolestes vorax'', dating back to ...
'' *** '' Thalassiodracon'' ***Subfamily
Brachaucheninae Thalassophonea is an extinct clade of pliosaurids from the Middle Jurassic to the early Late Cretaceous (Callovian to Turonian) of Australia, Europe, North America and South America. ''Thalassophonea'' was erected by Roger Benson and Pat ...
**** ''
Brachauchenius ''Brachauchenius'' (meaning 'short neck') is an extinct genus of pliosaurid that lived in North America (United States) and Morocco during the Late Cretaceous. History The type species, ''Brachauchenius lucasi'', lived in the Western Inland ...
'' **** ''
Kronosaurus ''Kronosaurus'' ( ; meaning "lizard of Kronos") is a potentially dubious genus of extinct short-necked pliosaur. With an estimated length of , it was among the largest pliosaurs, and is named after the leader of the Greek Titans, Kronos. It ...
'' **** '' Makhaira'' **** ''
Megacephalosaurus ''Megacephalosaurus'' (; "great-headed lizard") is an extinct genus of short-necked pliosaur that inhabited the Western Interior Seaway of North America about 94 to 93 million years ago during the Turonian stage of the Late Cretaceous, containin ...
'' **** ''
Polyptychodon ''Polyptychodon'' (meaning 'shaped fin tooth') is a genus of pliosaurid found in Middle-Late Cretaceous marine deposits in southern England, France and Argentina. It has been considered a ''nomen dubium'' in a 2016 review. History of discovery ...
'' **** '' Sachicasaurus'' **** '' Monquirasaurus'' **** '' Stenorhynchosaurus'' **** ''
Luskhan ''Luskhan'' (meaning "water spirit chief") is an extinct genus of brachauchenine pliosaur from the Cretaceous of Russia. The type and only species is ''Luskhan itilensis'', named by Valentin Fischer and colleagues in 2017 from a well-preserv ...
''


Phylogeny

Pliosauroidea is a stem-based taxon that was defined by Welles as "all taxa more closely related to '' Pliosaurus brachydeirus'' than to ''
Plesiosaurus dolichodeirus ''Plesiosaurus'' (Greek: ' ('), near to + ' ('), lizard) is a genus of extinct, large marine sauropterygian reptile that lived during the Early Jurassic. It is known by nearly complete skeletons from the Lias of England. It is distinguishable ...
''". 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 A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
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 Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
. 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 In the geologic timescale, the Kimmeridgian is an age in the Late Jurassic Epoch and a stage in the Upper Jurassic Series. It spans the time between 157.3 ± 1.0 Ma and 152.1 ± 0.9 Ma (million years ago). The Kimmeridgian follows the Oxford ...
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 Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
by Hahnel. The remains originally contained part of a rostrum with teeth (now lost). In August 2006, palaeontologists of the
University of Oslo The University of Oslo ( no, Universitetet i Oslo; la, Universitas Osloensis) is a public research university located in Oslo, Norway. It is the highest ranked and oldest university in Norway. It is consistently ranked among the top universit ...
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 ''Pliosaurus'' (meaning 'more lizard') is an extinct genus of thalassophonean pliosaurid known from the Kimmeridgian and Tithonian stages (Late Jurassic) of Europe and South America. Their diet would have included fish, cephalopods, and marine ...
''. In the summer of 2008, the fossil remains of the huge pliosaur were dug up from the permafrost on
Svalbard Svalbard ( , ), also known as Spitsbergen, or Spitzbergen, is a Norwegian archipelago in the Arctic Ocean. North of mainland Europe, it is about midway between the northern coast of Norway and the North Pole. The islands of the group rang ...
, a Norwegian island close to the
North Pole The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where the Earth's axis of rotation meets its surface. It is called the True North Pole to distinguish from the Ma ...
. The excavation of the find is documented in the 2009
History History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as well ...
television special
Predator X ''Pliosaurus'' (meaning 'more lizard') is an extinct genus of thalassophonean pliosaurid known from the Kimmeridgian and Tithonian stages (Late Jurassic) of Europe and South America. Their diet would have included fish, cephalopods, and marin ...
. On 26 October 2009, palaeontologists reported the discovery of potentially the largest pliosauroid yet found. Found in cliffs near Weymouth,
Dorset Dorset ( ; archaically: Dorsetshire , ) is a county in South West England on the English Channel coast. The ceremonial county comprises the unitary authority areas of Bournemouth, Christchurch and Poole and Dorset. Covering an area of , ...
, on Britain's
Jurassic Coast The Jurassic Coast is a World Heritage Site on the English Channel coast of southern England. It stretches from Exmouth in East Devon to Studland Bay in Dorset, a distance of about , and was inscribed on the World Heritage List in mid-Decembe ...
, the fossil had a skull length of . 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''.


References


External links


The Plesiosaur Directory - pliosaur page

Large pliosaur from the Jurassic Coast, Dorset - BBC News

Dorset pliosaur skull after conservation - video. BBC July 2011


{{Taxonbar, from=Q843192 Plesiosaurs Hettangian first appearances Cenomanian extinctions