Classification

Sauropterygia > Eosauropterygia > Eusauropterygia > Pistosauroidea > Plesiosauria >

Pliosauroidea > Pliosauridae

Synonyms: 'Stretosaurus' but maybe not! (Noe, pers. comm. 2003)

Species:

L. ferox Sauvage, 1873 (Type species)

Material

Known from various more or less complete skeletons. However, the holotype is only a single tooth.

Distribution

Type locality: Callovian, Oxford Clay, Peterborough, England. Also known from Bedfordshire (UK), Cambridgeshire (UK), France (near Boulogne) and possibly Chile.

Images

Title image at top of page: a photograph of a skeleton (approx. 4.5 metres long) of L. ferox in the Tubingen Museum. The rear of the skull is fabricated, From Martill and Naish (2000)

Three close up shots of the Liopleurodon mount in Tubingen, Germany. All used by kind courtecy of Markus Felix Bühler (many thanks 'Sordes').

Life restoration of Liopleurodon ferox (original artwork by Adam S. Smith)

Liopleurodon ferox skull in outline in lateral view and posterior view, as reconstructed by Noe et al (2003). Abbreviations: en, external naris; or, orbit; tf, temporal fenestra; pr, prootic; s, supraoccipital; eo, exoccipital-episthotic; ep, epipterygoid; bs, basisphenoid; bo basioccipital; qpt, quadrate pterygoid flange.

L. pachydeirus (Seeley, 1869)

Material

Holotype = associated cervical vertebrae

Distribution

Oxford Clay, Great Gransden, UK

Species notes: Differs from L. ferox in features of the teeth and cervical vertebrae: enamel ridges closely packed on inner surface and 6-7 evenly spaced ridges on outer surface, cervical vertebrae with faint ventral keel (Tarlo, 1960).

L. rossicus (Novozhilov, 1948)

Material

most of a skull and pectoral girdle

Distribution

Middle Volgian (Dorsoplanites panderi Zone), Buinsk Mine Oil Shales, Ibresi Disatrict, right bank of river Volga, Autonomous republic of Chuvashia, Russia.

Images

Reconstruction of the skull of L. rossicus (from Novozhilov, 1948). May not in fact belong to Liopleurodon. Abbreviations: Pmx, premaxilla; Mx, maxilla; Na, nasal; Prf Prefrontal, La, lachrimal; Fr, frontal, Pof, postfrontal; PoO, postorbital; Jug, jugal, Pa, parietal; Sq, squamosal.

L. macromerus (Phillips) (1871?)

Material

most of a skull and pectoral girdle

Distribution

Middle Volgian (Dorsoplanites panderi Zone), Buinsk Mine Oil Shales, Ibresi Disatrict, right bank of river Volga, Autonomous republic of Chuvashia, Russia.

Discussion

Diagnosis- Liopleurodon differs from Pliosaurus in the following characters: mandibular symphysis relatively short (5-7 teeth), each ramus (jaw) contains 25-28 teeth, fewer longitudinal ridges on outer surface of teeth than on inner surface, long epipodials. The teeth of callovian species (L. ferox) are circular in cross section, but become trihedral in later Kimmeridgian species (L. rossicus, L. macromerus). A similar trend occurs in the closely related genus Pliosaurus. The interelationships of Jurassic pliosaurus are still poorly understood and the species macromerus, included by some authors in Pliosaurus, may resolve to be a distict genus.

Toys

Liopleurodon links -best on the web

http://www.abc.net.au/dinosaurs/fact_files/sea/liopleurodon.htm and http://www.bbc.co.uk/science/seamonsters/factfiles/liopleurodon.shtml for the best animated restoration of Liopleurodon to date, whether you believe the alternating fore-hind flipper theory or not.

http://www.plesiosaur.com/liopleurodon.htm on how big Liopleurodon really was.

http://plesiosaur.com/taxonomy/pliosauridae.htm an exhaustive list of all material pertaining to Liopleurodon

http://www.saurierausstellung.de/saurier/fileadmin/gfx/inhalte/liopleurodon_rossicus.jpg nice picture of Liopleurodon rossicus' skull

SPECIAL FEATURE -

modified from a short undergraduate project undertaken at the University of Portsmouth (2001):

Liopleurodon skull from the Oxford Clay of England

Location and stratigraphy

Middle Jurassic Oxford Clay, Middle Callovian stage. This genus is known from the UK: Bedfordshire, Cambridgeshire, Peterborough, France (near Boulogne) and possibly Chile. Two species of Liopleurodon are known from the Oxford Clay, L. ferox and the rarer L. pachydeirus. Generally Liopleurodon has a relatively frequent abundance (Martill 1994).

Description

General

The whole specimen is 106cm long and 58cm wide. The skull has been preserved ventral side up, exposing both of the dentary rami and the right hand side of the most anterior part of the skull consisting of premaxilla, maxilla (both with associated alveoli and teeth), several loose teeth, rib fragments and a number of vertebrae. The rear of the cranium is also exposed in places (text-figs 1, 2 and 3). The specimen also yields an array of invertebrate fossils: ammonites, gastropods and dis-articulated bivalves.

TEXT-FIG 1. Photographs of the specimen with ruler for scale. a) Taken from above exhibiting the ventral surface. Note the large mandibular symphysis and range of alveoli. The largest rib is at the top of the shot. b) Lateral view. Anterior is to the left of the shot.

TEXT-FIG 2 (left) Annotated illustration of the fossil in ventral view.

TEXT-FIG 3 (right) Annotated illustration of the fossil in right lateral view.

Cranium

The total length of cranium exposed is 59 cm. The right maxilla and premaxilla are mostly exposed and the whole of the broadly undulating ventral margin can be traced. In lateral view it is deepest immediately posterior of the maxilla-premaxilla suture. The maxilla it is elongate and gently curves inwards (medially) towards the anterior. It meets the premaxilla along a poorly defined suture, which runs down from the dorsal to the ventral surface at an inclination of 45 degrees to the long axis of the skull. The right premaxilla joins with the right maxilla (unexposed/absent) to form a symphysis. The maxilla-premaxilla complex bears 21 spherical alveoli, 15 of which are completely exposed exhibiting varying diameters (Table 1). It is possible to observe the curved lower margin of the orbit. Matrix obscures the other bones of the cranium but it is possible to make tentative identifications of the poorly exposed bones (text-fig 2)

Text-fig 4. Reconstruction of the skull as it would have been before fossilization.

Table 1 Alveoli diameter

Dentary

Both rami are exposed in this specimen although dislocated and with transverse fractures in many places (Text-fig 2). The right ramus is almost totally exposed and is 70cm long. The left ramus is partially exposed revealing only 21cm of the entire length. The dentary is elongate with slight variations in width along the length of each ramus. The well exposed ramus is thickest at the symphysis 12cm from the anterior tip where it measures 10cm thick. At the very tip it tapers to a rounded point. At the anterior three alveoli are exposed in transverse cross section, due to damage of the bone (due to damage during excavation). They are filled with dark gray matrix.

Teeth

There are 7 caniniform teeth in the specimen, 4 are loose in the surrounding matrix. No whole teeth are exposed but one large fragment is 19 mm long. The estimated total length of this tooth is 25mm (without root). This is small in comparison with isolated teeth which have been discovered up to 45cm in length (with root) (Martill pers. comm. 2001). Of the teeth present only 2 are complete enough to show detail. The crowns are conical, slightly curved with fluted keels and distinct ribbing. Some individual ribs are continuous from the tooth tip to the base of the tooth where it meets the root while other ribs are not. The root is exposed in the tooth residing in the 2^nd alveoli. It is extremely smooth and also appears to curve slightly. It forms the thickest part of the tooth.

Vertebrae

There are 5 disarticulated and distorted vertebrae clustered together at the posterior end of the specimen. They are small (in comparison to the skull) with an average maximum span of 3cm.

Ribs

Two rib segments are present, the one closest to the dentary is 15cm long with a maximum width of 14mm .The end furthest away from the dentary is slightly splayed, this is the proximal part of the rib. The second rib segment is 9 cm long. A deep furrow runs down the length of each segment giving a figure of eight appearance in transverse cross-section.

Other Features

The surface of the bone varies in texture. It is distinctly rough in some places (especially on the maxilla), smooth or striated in others (the dentary is especially highly variable in texture). The selection of fossil invertebrates immediately indicates a marine environment and can also give an indication of the exact age of the specimen. Most of the invertebrates are either poorly preserved or poorly exposed so classification is difficult. One distinct ammonite however can be identified as the genus Kosmoceras and the single row of lateral tubercules makes it likely to be K. jason. The biozone of this species represents the lower part of the Middle Callovian stage. The dental pattern of the premaxilla-maxilla exhibits a generally constant diameter of alveolus at the posterior of the jaw with only a 4mm range of variability. Larger diameters form two peaks, both towards the anterior. The most anterior peak represents the symphysis while the second peak lies just posterior to the symphysis. The larger alveoli housed the largest teeth, which would in life all occur at the anterior end of the jaws. The fact that pliosaurs have deep-rooted teeth is an attribute evident even though many of the teeth in this specimen are dislodged or missing. The evidence comes from the deeply set, high rimmed alveoli and also from the exposed tooth root which is thick with no thinning, thus indicating penetration into the maxilla to a considerable depth. The textured bone surface may be representative of a juvenile pliosaur, not fully grown. Certainly, this genus is known from much larger specimens in some cases with skulls up to three meters in length (Martill 1991). Pliosaurs have indeterminate growth i.e. no upper limit (Martill pers. comm. 2001), so completely fully formed bone in pliosaurs should not be expected. However, the poorly defined sutures indicate an individual of considerable age. Alternatively the grooves and ridges may have held capillaries for supplying blood to sensitive tissue around the mouth. Pliosaurs are classified at species level predominantly on the dental ornamentation and it is on this basis that this specimen can be designated as L. ferox. Widely spaced tooth ridges with relatively deep furrows and staggered lengths justify this decision.The reconstructed skull appears elongate with a large orbit and antorbital fenestra (Text-fig 4). The data obtained from this study has implications for feeding and senses in pliosauroids.

Acknowledgments

Thanks go to the following people for their help and advice throughout the course of this project: Dr Dave Martill, Dr Mike Barker, Lorna Steele and Bob Loveridge from the University of Portsmouth. Also Lloyd Runham, Simon Clabby and Matt Round.

Page last updated June 2007. Adam Stuart Smith.