Eardasaurus powelli: A new Pliosaurid from England's Middle Jurassic Oxford Clay Formation.

The earliest known Pliosaurid Plesiosaurians date from rocks of the Earliest Jurassic. Long-snouted forms showing adaptations to for a specialist piscivoran diet appearing by the end of the Early Jurassic. Classical 'pliosauromorph' forms with large bodies, short necks, and heads which form a high proportion of the total body-length, appearing by the Middle Jurassic, and reaching sizes of 10-12 m by the Late Jurassic. This bodyform then remained essentially unchanged until the group disappeared in the early Late Cretaceous.

One of the most important deposits for the study of this group is the Oxford Clay Formation of England, which has been studied since the nineteenth century, and has produced a large and diverse assemblage of Plesiosaurs, with at least five valid described species: Simolestes vorax, Liopleurodon ferox, Peloneustes philarchus, 'Pliosaurus' andrewsi, and Marmornectes candrewi (a sixth, Pachycostasaurus dawni, is problematic, since it was described from a juvenile specimen that could potentially belong to several of the other species). Many of these are known from multiple specimens, notably Peloneustes philarchus, of which 21 examples have been found.

Many of these specimens, as well as other spectacular fossils from the same formation, were collected from pits which primarily extracted clay for the brick-making industry. The heyday of this industry was in the second half of the nineteenth century, when the brothers Charles and Alfred Leeds collected numerous Plesiosaur (and other) specimens from the clay pits around Peterborough in Cambridgeshire, including the holotypes of Simolestes vorax and 'Pliosaurus' andrewsi. The brick-making industry has declined greatly since this time, with a subsequent decline in the amount of activity at clay pits, and therefore the number of fossils recovered from them, but spectacular new finds are still reported from time to time, with the most recently described Oxford Clay Plisiosaur, Marmornectes candrewi, having been recovered from a clay pit in Bedfordshire in 1998.

In a paper published in the journal Acta Palaeontologica Polonica on 23 May 2022, Hilary Ketchum of the Oxford University Museum of Natural History, and Roger Benson of the Department of Earth Sciences at the University of Oxford, describe a new species of Pliosaurid from the Peterborough Member of the Oxford Formation, collected from the former ARC Cassington gravel pit near Yarnton, Oxfordshire.

The new Pliosaur is named Eardasaurus powelli, where 'Eardasaurus' is a combination of the  Old English 'eard', meaning 'native soil or dwelling', from which the village name Yarnton was derived, and '-saurus' the Greek for Lizard, commonly used as a suffix for large Mesozoic Animals, while 'powelli' honours Philip Powell, former Assistant Curator at the Oxford University Museum of Natural History, who took part in the excavation of the specimen from which the species is described in 1994, and carried out preparation work on its skull and postcranial skeleton.

The species is described from a single specimen, OUMNH PAL-J.2247, which was discovered during the construction of a deep silt pond. This specimen was partially embedded in six concretions, which enclosed the posterior two-thirds of the cranium, parts of the vertebral series, and the hindlimb.

Holotype of the Pliosaurid Plesiosaur Eardasaurus powelli (OUMNH PAL-J.2247) from the Middle Jurassic of Yarnton, Oxfordshire, UK. Photograph of the specimen on display in Oxford University Museum of Natural History. Skeleton laid out as discovered, with the exception of the left hindlimb (highlighted in black), which was originally disarticulated. An artist’s reconstruction of Eardasaurus powelli  is partially visible in the top right-hand side of the image. Ketchum & Benson (2022).

Specimen OUMNH PAL-J.2247  measures approximately 4.7 m long from the tip of the snout to the end of the (incomplete) tail, as preserved, and includes the cranium, lower jaw, four scleral ossicles, two hyoids, more than 40 teeth and tooth fragments (including both disarticulated and in situ teeth), atlas-axis complex, 57 postaxial vertebrae (comprising 18 cervicals, 3 pectorals, 24 dorsals, 4 sacrals, and 8 caudals, along with disarticulated neural arches, neural spines, ribs, and chevrons), and 11 gastralia. The preserved appendicular skeleton includes the distal end of the right humerus plus a partial left forelimb discovered in articulation, which includes the radius, ulna, proximal and distal carpals, and 17 phalanges. There is a partial left hindlimb compri sing the femur, proximal and distal tarsals. In total 40 complete phalanges, plus six partial phalanges were found disarticulated and cannot confidently be assigned to any particular limb. Of the limb girdles, only the interclavicle and a clavicle are preserved.

Eardasaurus powelli is a Longirostrine Pliosaurid with a high number (35-40) of alveoli on its maxilla, a jugal with fluted ornamentation on its orbital margin, a step-like contact between the jugal and the squamosal, a 'lacrimal' bone formed by the neomorphic ossification in the anteroventral orbit margin (and not homologous to the lacrimal of other Tetrapods) which is dorsoventrally slender with a posterior rod-like projection.

Eardasaurus powelli also has a pattern of enamel ridges on its larger (mesial) teeth, something also seen in Peloneustes philarchus, but absent in other Pliosaurids from the Oxford Clay. It also has five to six premaxillary teeth, a  prominent mediolateral constriction of the rostrum at the premaxilla–maxilla suture, a diastema (gap) between premaxillary and maxillary dentitions, a  maxilla excluded from contact with the medial margin of external naris by an anterior extension of the frontal, a proportionally elongate posterior interpterygoid vacuities compared to other Middle Jurassic Pliosaurids, a mediolaterally expanded mandibular symphysis, nine pairs of dentary teeth adjacent to the mandibular symphysis, a  splenial which encloses the posterior margin of the anterior opening of Meckel’s canal, and a coronoid exposed on the lateral surface of the mandible, a strongly convex medial expansion of the surangular in dorsal view.

Holotype of the Pliosaurid Pleasiosaur Eardasaurus powelli (OUMNH PAL-J.2247) from the Middle Jurassic of Yarnton, Oxfordshire, UK. Cranium in dorsal view. Photograph (A₁), interpretive drawing (A₂), light grey, broken bone; mid grey filler; dark grey, matrix. Ketchum & Benson (2022).

A phylogenetic analysis carried out by Ketchum and Benson recovered Eardasaurus powelli as an early-diverging Thalassophonean Pliosaurid, forming the sister taxon to the derived group comprising 'Pliosaurus' andrewsi, Simolestes vorax, Liopleurodon ferox, Pliosaurus spp., and Brachaucheninae.

Phylogenetic topology for Pliosauridae, focussing on Early–Middle Jurassic representatives, based on Bayesian Mkv analysis. Numbers indicate posterior support for nodes demonstrating strong support for many aspects, but weaker support for relationships among Peloneustes philarchus, Anguanax zignoi, and Eardasaurus powelli, which are tentatively recovered as grade leading to more derived Pliosaurids. Ketchum & Benson (2022).

Eardasaurus powelli has a pattern of deep ridges on its teeth which would have formed additional deep cutting surfaces in life. Such ridges are ecologically significant, as they are typically associated with macropradatory behaviour (i.e. attacking large prey). Such ridges are found in a range of taxa, although they are rare (but not unknown) in Pliosaurids, although Ketchum & Benson suggest that this may be due to under-reporting rather than a true absence.

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Arminisaurus schuberti: A new species of Pliosaur from the Early Jurassic of North Rhine-Westphalia, Germany.

The Plesiosaurs were Mesozoic marine reptiles that arose in the Late Triassic or Early Jurassic and persisted till the Late Cretaceous. They were related to modern lizards and snakes, but were fully aquatic, the largest species reaching 15 m in length. All species seem to have been strict carnivores, and at least one species gave birth to live young. Plesiosaurs are thought to have been fully aquatic from their first appearance; having evolved from Nothosaurs, a group of semi-aquatic marine Reptiles. The Plesiosaurs are divided into two groups, the short-necked Pliosaurs and the long-necked Elasmosaurs.

In a paper published in the journal Alcheringa on 15 September 2017, Sven Sachs of the Naturkunde-Museum Bielefeld, and Benjamin Kear of the Museum of Evolution at Uppsala University, describe a new species of Pliosaur from the Early Jurassic Amaltheenton Formation of Bielefeld in North Rhine-Westphalia, northwest Germany.

The new species is named Arminisaurus schuberti, where 'Arminisaurus' honours Arminius, a chieftan of the Germanic Cherusci people, who defeated three Roman legions under Publius Quinctilius Varus at the Battle of the Teutoburg Forest in 9 AD, and 'schuberti' honours Siegfried Schubert, who obtained the specimen from which the species is described from the Beukenhorst-II industrial clay pit in the Bielefeld. The species is named from a fragmentary specimen comprising the posterior section of the right mandibular ramus with the surangular, angular, prearticular and articular, eight isolated teeth and other dental fragments, ten cervical vertebrae, an incomplete pectoral vertebra, at least seven dorsal vertebrae, seven caudal vertebrae and various cervical-, dorsal-, possible sacral-caudal- and gastral ribs, as well as components of what may be the clavicle and interclavicle, together with the complete right and partial left scapula, a propodial, epipodial, six mesopodials and 19 phalanges abd other indeterminate bone fragments.

Arminisaurus schuberti, dorsal vertebra in (A) anterior and (B) lateral view. Dorsal neural spine in anterior view (C). Caudal vertebra in (D) articular, (E) lateral, (F) dorsal and (G) ventral views. Dorsal rib (H), caudal rib or hemapophysis (I), gastral rib (J) and ?sacral rib (K). Scale bars are 30 mm. Abbreviations: con, concavity; hf, hemapophyseal facet; nc, neural canal; ns, neural spine; rf, rib facet; tp, transverse process. Sachs & Kear (2017).

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Stenorhynchosaurus munozi: A new species of Pliosaur from the Early Cretaceous of Columbia.

The Pliosaurs were Mesozoic Marine Reptiles related to modern Lizards and Snakes, but were fully aquatic, the largest species reaching 15 m in length. Plesiosaurs are thought to have been fully aquatic from their first appearance; they arose in the Late Triassic or Early Jurassic and persisted till the Late Cretaceous, though there are gaps in their fossil record; periods where they are poorly known, but must have existed as they left decendents. One such period is the Early Cretaceous, from when very few Pliosaurs are known. One site known to produce Pliosaurs from this time is at Villa de Leiva in the Colombian Andes, from where one species is known has been described and a second well preserved specimen is known.

In a paper published in the journal Revista de la Academia Colombia de Ciencias Exactas, Físicas y Naturales on 5 June 2016, María Eurídice Páramo-Fonseca of the Departamento de Geociencias at the Universidad Nacional de Colombia, Marcela Gómez-Pérez and Leslie Noé of the Departamento de Geociencias at the Universidad de los Andes, and Fernando Etayo-Serna of the Servicio Geológico Colombiano formerly describe the second Villa de Leiva Pliosaur specimen as a new species.

The specimen is named Stenorhynchosaurus munozi, where 'Stenorhynchosaurus' means 'narrow snouted Lizard' and 'munozi' honours Jorge Muñoz, who discovered the specimen on his land, and donatd it to the Museo Geológico José Royo y Gómez of the Servicio Geológico Colombiano. Stenorhynchosaurus munozi is a short-necked Pliosaurid Plesiosaur (as oposed to a lomg-necked Plesiosaurid Pliosaur). The specimen is well preserved, lacking only the tip of the snout, part of the front left paddle, the entire hind right paddle and tail, and with part of the cranium slightly crushed.

Stenorhynchosaurus munozi. General view of the specimen in dorsal view. Photography in the field and interpretation of the skeleton. Páramo-Fonseca et al. (2016).

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A Pliosaur from the Jurassic Coast of Dorset. The Pliosaurs were Mesozoic marine reptiles that arose in the Late Triassic or Early Jurassic and persisted till the Late Cretaceous. They were related to modern lizards and snakes, but were fully aquatic, the largest species reaching 15 m in length. All species seem to have been strict carnivores, and at least one species gave birth to live young. Plesiosaurs are thought to have been fully aquatic from their...

An Early Jurassic Pliosaur from Normandy. The Pliosaurs were Mesozoic marine reptiles that arose in the Late Triassic or Early Jurassic and persisted till the Late Cretaceous. They were...

A Pregnant Plesiosaur.                                 The plesiosaurs were a group of marine reptiles...

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A Pliosaur from the Jurassic Coast of Dorset.

The Pliosaurs were Mesozoic marine reptiles that arose in the Late Triassic or Early Jurassic and persisted till the Late Cretaceous. They were related to modern lizards and snakes, but were fully aquatic, the largest species reaching 15 m in length. All species seem to have been strict carnivores, and at least one species gave birth to live young. Plesiosaurs are thought to have been fully aquatic from their first appearance; they are thought to have evolved from Nothosaurs, a group of semi-aquatic marine Reptiles. The term Sauropterygians is used to include the Nothosaurs and the Pliosuars, plus the Pachypleurosaurs; Lizard-like aquatic Reptiles. The Sauropterygians are considered to be the sister group of the Squamates - Snakes and Lizards.

In a paper published in the journal PLoS One on 31 May 2013, a team of scientists led by Roger Benson of the Department of Earth Sciences of the University of Oxford describe a new species of Pliosaur from the Late Jurassic of the Dorset coast in southern England.

The new species is named Pliosaurus kevani, after Kevan Sheehan of Osmington Mills in Dorset, who collected the specimen in pieces from fallen blocks on the foreshore at Osmington over a period of eight years. The assembled specimen is a nearly complete skull 1995 mm in length and 730 mm across, the cranium comprising 57% of the skull length, and the snout the remainder.

Cranium of Pliosaurus kevani in dorsal view, photograph (A) and line drawing (B). Dark grey tone represents broken bone surface, mid grey represents matrix, and light grey represents tooth or artificial restoration. Abbreviations: bat, basal tuber; en, external naris; exoc-opis, exoccipital opisthotic; fr, frontal; jug, jugal; lac, ‘lacrimal’; mx, maxilla; pal, palatine; par parietal; pmx, premaxilla; po, postorbital; pofr, postfrontal; prfr, prefrontal; pt, pterygoid; rug, rugose eminence; soc (l), left portion of supraoccipital; soc (r), right portion of supraoccipital; sq, squamosal. 

Scale bar equals 500 mm. 

Benson et al. (2013).



Cranium of Pliosaurus kevani in ventral view. In line drawing (B) dark grey tone represents broken bone 

surface, mid grey represents matrix, and light grey represents tooth or artificial restoration. Abbreviations: bat, basal tuber; cfps, cultriform process of 

the parasphenoid; ecto, ectopterygoid; exoc-opis, exoccipital-opisthotic; in, internal naris; jug, jugal; mx, maxilla; mx19, 19th maxillary alveolus; occ, 

occipital condyle; pal, palatine; pal-pt, palatine-pterygoid contact; palf, palatal fenestra; par, parietal; pmx, premaxilla; ps, parasphenoid; pt, pterygoid; 

soc (l), left portion of supraoccipital; sof, suborbital fenestra; sq, squamosal; vom, vomer; vom-pt, vomer pterygoid contact. Scale bar equals 500 mm. 

Benson et al. (2013).

Pliosaurus kevani is a Late Jurassic Pliosaur dated to the Rasenia cymodoce biozone of the Lower Kimmeridgian, making it between 155.7 and 150.8 million years old. It is large for a Pliosaur of this age, though fragmentary material from specimens thought to be of similar size has been found previously. Pliosaurs appear to have grown in size steadily from the appearance of the group until the Early Cretaceous, with later Cretaceous members of the group growing slightly smaller again. The largest Early Cretaceous Pliosaurs exceeded 2360 mm in skull length, with some fragmentary material from animals estimated to be far larger.

Reconstruction of the skull of Pliosaurus kevani in right lateral (A), dorsal (B), and ventral (C) views. Abbreviations: ang, angular; art, articular; den, dentary; en, external naris; exoc-opis, exoccipital-opisthotic; in, internal naris; jug, jugal; fr, frontal; lac, ‘lacrimal’; mx, maxilla; occ, occipital condyle; pal, palatine; palp, palpebral; par, parietal; pifor, pineal foramen; pmx, premaxilla; po, postorbital; pofr, postfrontal; prfr, prefrontal; proo, prootic; ps, parasphenoid; pt, pterygoid; sa, surangular; soc, supraoccipital; sq, squamosal; vom, vomer. Total skull length is approximately 2 meters. Benson et al. (2013).

The location where Pliosaurus kevani was recovered. Scale bar is 500 m. Benson et al. (2013).

See also New species of Placodont from the Middle Triassic of the Netherlands, A Plesiosaur from the Early Jurassic of Portugal, An Early Jurassic Pliosaur from Normandy, A Pregnant Plesiosaur and The Weymouth Pliosaur.

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An Early Jurassic Pliosaur from Normandy.

The Pliosaurs were Mesozoic marine reptiles that arose in the Late Triassic or Early Jurassic and persisted till the Late Cretaceous. They were related to modern lizards and snakes, but were fully aquatic, the largest species reaching 15 m in length. All species seem to have been strict carnivores, and at least one species gave birth to live young.

A forthcoming paper in the journal Acta Palaeontologica Polonica by Peggy Vincent of the Département Histoire de la Terre at the Muséum National d’Histoire Naturelle and the Staatliches Museum für Naturkunde, Nathalie Bardet, also of the Département Histoire de la Terre at the Muséum National d’Histoire Naturelle and Emanuela Mattioli of the Laboratoire de Géologie de Lyon at Université Lyon describes the discovery of a new Pliosaur from the Early Jurassic of Normandy.

The new Pliosaur has been identified from a partial skull and several vertebrae from the Pliensbachian (an Early Jurassic stage; roughly 183.0-189.6 million years ago) Roche-Blain Quarry, at Fresney-le-Puceux, near Laize-la-Ville, south of Caen. The skull is elongated and narrow, at about 470 mm. It does not closely resemble any previously known Pliosaur, and has been named as Cryonectes neustriacus, Cryonectes meaning cold swimmer (the Pliensbachian is thought to have been quite cool) and neustriacus meaning from Neustrie, a Frankish kingdom that covered much of northern France.

Ventral view of the skull of Cryonectes neustriacus. From Vincent et al. (2012).

See also A Pachycormiform Fish from the Lower Jurassic Posidonia Shale, A Pregnant Plesiosaur, The Weymouth Pliosaur and Reptiles on Sciency Thoughts YouTube.

A Pregnant Plesiosaur.

The plesiosaurs were a group of marine reptiles that appeared in the Middle Triassic, about 230 million years ago and went extinct in the KT extinction at the end of the Cretaceous, 65 million years ago. They are thought to have evolved from Nothosaurs, a group of semi-aquatic marine reptiles. The plesiosaurs are thought to have been fully aquatic from the outset. The term sauropterygians is used to include the nothosaurs and the plesiosuars, plus the pachypleurosaurs; lizard-like aquatic reptiles. The sauropterygians are thought to be related to the squamates - snakes and lizards.

A reconstruction of Pistosuarus, generally considered to be the earliest plesiosaur. It does not appear to be well suited to life on land.

The plesiosaurs are split into two taxonomic groups, the plesiosaurs proper and the pliosaurs (plus a few early species of uncertain affinities). The pliosuars were aquatic reptiles with short necks, elongated heads and powerful jaws, with many conical teeth (ideal for seizing large prey). They ranged from 4 m to 25 m in length and appeared in the Late Triassic, persisting till the end of the Cretaceous.

Reconstruction of a pliosaur attacking a mosasaur (large Mesozoic marine lizard) by paleo-artist Dan Varner.

The plesiosaurs proper are divided into five families, the Elasmosaurs, the Plesiosuarids, the Polycotylids, the Cimoliasaurs, and the Cryptoclids.

The elasmosaurs appeared in the Late Triassic; they had very elongate necks and small heads. The earliest species were about 3 m long, but some later species reached 14 m in length.

Reconstruction of Elasmosaurus by artist Doug Henderson.

The plesiosaurids currently include the single genus Plesiosaurus, the genus after which the whole group has been named. Since almost all plesiosaurs have started in this group then been moved out it is quite likely that this group will be further revised. Plesiosaurus was a long-necked, small headed form, though not as extreme as the Elasmosaurs. It is from the Lower Jurassic.

Reconstruction of Plesiosaurus by artist Adam Stuart Smith.

The polycotylids are a Cretaceous group with long snouts and short necks, superficially resembling the pliosaurs.

Reconstruction of Polycotylus by illustrator Carl Buell.

The cimoliasuars are probably an artificial group. The group includes a number of incomplete skeletons of plesiosaurs from the Jurassic and Cretaceous, as well as one (dubious) Palaeogene specimen. Cimoliasaurs tend to have intermediate neck and snout lengths.

The cryptoclidids are a group of medium sized plesiosaurs with long necks and broad, flat heads. They ranged from the Middle Jurassic to the end of the Cretaceous.

A reconstruction of Cryptoclidus, by palaeo-artist Alain Bénéteau.

A paper in the 12 August 2011 edition of the journal Science Robin O'Keefe of the Department of Biology at Marshall University and Luis Chiappe of the Natural History Museum of Los Angeles County describes for the first time a specimen of a plesiosaur which is apparently pregnant. If correct this settles a long standing dilemma for plesiosaur specialists. Plesiosaurs are clearly not not well adapted to land dwelling, so scientists had long suspected that they might be able to reproduce without venturing onto land. However no evidence of this had ever been found (unlike in ichthyosaurs, where the phenomenon is well documented), and not all reptiles have the potential to bear live young.

All crocodiles, most turtles and some birds and squamates (snakes and lizards) have temperature-dependent sex determination. This system uses an outside factor, temperature, to determine sex; above a certain temperature embryos will develop as one sex, bellow it as the other. This works fine for an egg-laying reptile, particularly one with a large brood size where there will be a temperature difference within the nest, but a large marine reptile is very likely to maintain a constant body temperature, which would result in all embryos developing as the same sex - not a good survival strategy.

Mammals, birds and most squamates use chromosomal sex determination. Under this system a species has sex two chromosomes. One chromosome is present in all individuals, the other only in individuals of one sex. Thus mammals have X and Y chromosomes; females have two X chromosomes males an X and a Y. Everyone inherits an X chromosome from their mother, and either an X or a Y chromosome from their father. All mammals develop as females, unless they have a Y chromosome.

This works well for mammals; the Y chromosome leads to the production of hormones that modify a potentially female animal to become male, but not so well for birds. Birds have sex chromosomes referred to as Z and W. A bird with two Z chromosomes in male, one with a Z and a W is female. In birds the presence of a W chromosome leads to the production of hormones that turn a potentially male individual female. This prevents the emergence of live births in birds; a baby bird developing inside its mother would be exposed to female hormones and develop as a female regardless of its chromosomes.

The sauropterygans (nothosaurs and plesiosaurs) are thought to be closely related the squamates, where chromosomal sex determination is the commonest method of sex determination, so it would not be surprising if this was the case in plesiosaurs.

In 2009 a paper in the Zoological Journal of the Linnean Society detailed a long-term study of sex-determination in squamates by Martina Pokorná and Lukáš Kratochvíl of the Department of Ecology at Charles University in Prague, which strongly indicated that the ancestral state in squamates was temperature dependent sex-determination, and that chromosomal sex determination has evolved several times within the group. Both the XY and ZW systems of sex determination are present within the squamates, and are likely to have evolved separately from a non-chromosomal system. This implies that the common ancestor of the sauropterygans and squamates used a temperature dependent sex determination system; the most that can be said is that the groups clearly had the potential to develop chromosomal sex determination.

The pregnant specimen described by O'Keefe and Chiappe (LACM 129639) was discovered in Kansas in the 1980s, and has been in the collection of the Natural History Museum of Los Angeles County ever since. It is not immediately obvious that this is a pregnant specimen; the fetus is not intact could potentially be the last meal of the adult rather than its young, though the pregnancy theory is supported by the absence of more common food material such as belemnites (Mesozoic molluscs) etc.

LACM 129369.

In addition LACM 129369 is a Polycotylus latippinis from the very end of the Cretaceous. P. latippinis is a highly derived species, not thought to be ancestral to any other form of plesiosaur, so it cannot be used to directly infer that other species bore live young. It would clearly have been useful to a plesiosaur, and it is considered likely that the ability arose in a nothosaur ancestor of the plesiosaurs. However this remains just as much a theory as it did before the re-examination of specimen LACM 129369.

A reconstruction of Polycotylus as a live-birthing animal, by science illustrator Stephanie Abramowicz.

See also The Weymouth Pliosaur and Reptiles on Sciency Thoughts YouTube.

The Weymouth Pliosaur.

On the eighth of this month (July 2011) celebrated naturalist and broadcaster David Attenborough unveiled Dorset County Museum's newest attraction, the 2.4 m long fossilized skull of a Jurassic pliosaur from the coast of Weymouth Bay. The first parts of the skull were uncovered by a landslip in 2003, and found by amateur palaeontologist Kevin Sheehan, who collected the pieces of the skull one at a time over the next three years.

It is estimated the complete animal would have been about eighteen meters long, and the museum suspect that it may represent a new species of pliosaur, though it has not yet been formally described, and will not be until further studies are completed. The museum has made the skull the centerpiece of a display with the title 'The World's Biggest Bite'. Palaeontologist Hans Sues, of the Smithsonian National Museum of Natural History in Washington DC, in an e-mail to National Geographic Magazine, suggests that this may be premature, as pliosaurs are large animals and newer, larger specimens are not a surprise. He also questions the evidence for this claim, which has not been presented in any formal scientific literature. This seems a little churlish, as a scientific display for tourists is not a serious scientific statement, and the term 'World's Biggest Bite' does not actually mean very much - claiming the animal had the largest jaws or the hardest bite would mean more.

Weymouth Bay forms part of the Jurassic Coast, a 150 km stretch of coast running from Budleigh Salterton in Devon to Wareham in Devon, along which 185 million years of Triassic and Jurassic history are exposed. The Jurassic Coast was the first site in the UK to be granted World Heritage Site status by UNESCO. The Weymouth Pliosaur is about 155 million years old, making it Oxfordian or Kimmeridgian in age. The Oxfordian and Kimmeridgian are 'stages', subdivisions of the Jurassic 5.5 million and 4.9 million years long respectively. These were periods of extreme global warming, in which Britain was more or less completely covered by warm, tropical seas, and marine reptiles grew to extra-ordinary sizes.

The pliosaurs were a group of large plesiosaurs with elongated, powerful jaws, and short necks. The plesiosaurs were a highly successful group of Mesozoic marine reptiles, which evolved from lizard-like ancestors in the early Triassic. They had large powerful bodies, flipper-like limbs and short tails. They were not closely related to the dinosaurs (scientists are uncertain which group of reptiles the plesiosaurs are most closely related to, due to their highly derived bodies), but like them flourished throughout the Mesozoic, going extinct abruptly at the end of the Cretaceous.

See also The Ashdown Maniraptoran.