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Megacephalosaurus eulerti is a large macropredatory plesiosaur representing one of the last members of the diverse pliosaurid clade Brachaucheninae. The taxon was established upon a nearly complete skull including the mandible and fragments of the postcranial skeleton originating from the lower middle Turonian (Upper Cretaceous) of Kansas, USA. Owing to its age, reasonable completeness and its state of preservation, M. eulerti bears important anatomical details regarding the last brachauchenines. Here we assess the dentition of the taxon, compare the teeth to those of other thalassophonean pliosaurids and comment on the utility of these results for inferences of the phylogenetic relationships of the last brachauchenines. Additionally, we provide remarks on the cranial anatomy of M. eulerti, revise character scores of this taxon used in current phylogenetic studies and address the phylogenetic relationships within Brachaucheninae. Parsimony analyses, aimed to test different character sampling and tree-search strategy, inferred only a single unambiguous synapomorphy uniting a clade formed by mid- to Late Cretaceous brachauchenines: presence of subcircular rather than subtrihedral/trihedral cross-sectional shape of the teeth. Still, the last brachauchenines (Brachauchenius and Megacephalosaurus) can be roughly characterized by a switch from anisodont to subisodont dentition and reduction of their tooth count. Nevertheless, the overall knowledge of the origin, phylogenetic relationships and distinguishability of brachauchenine pliosaurids remains poor and represents a subject for further extensive studies and modifications in taxon and character sampling.

Brachauchenine pliosaurids were a cosmopolitan clade of macropredatory plesiosaurs that are considered to represent the only pliosaurid lineage that survived the faunal turnover of marine amniotes during the Jurassic- Cretaceous transition. However, the European record of the Early to early Late Cretaceous brachauchenines is largely limited to isolated tooth crowns, most of which have been attributed to the classic Cretaceous taxon Polyptychodon. Nevertheless, the original material of P. interruptus, the type species of Polyptychodon, was recently reappraised and found undiagnostic. Here, we describe a collection of twelve pliosaurid teeth from the upper Albian-middle Cenomanian interval of the condensed, phosphorite-bearing Cretaceous succession at Annopol, Poland. Eleven of the studied tooth crowns, from the Albian and Cenomanian strata, fall within the range of the morphological variability observed in the original material of P. interruptus from the Cretaceous of England. One tooth crown from the middle Cenomanian is characterized by a gently subtrihedral cross-section. Similar morphology has so far been described only for pliosaurid teeth from the Late Jurassic and Early Cretaceous. Even though it remains impossible to precisely settle the taxonomic distinctions, the studied material is considered to be taxonomically heterogeneous.

This research presents the first pliosaur remains from the Upper Jurassic of the Atacama Desert, in northern Chile. Two specimens recovered from Oxfordian levels, are represented by a fragmentary mandibular ramus and by an associated humerus and femur, respectively. Previous to this research, the Jurassic South American pliosaur records were restricted to Tithonian endemic taxa from the Neuquen Province, in Argentina. The studied material represents the first of Oxfordian age known in Gondwana, adding to the scarce pliosaur records of Oxfordian age known worldwide.

Pliosaurid marine reptiles played important roles in marine food chains from the Middle Jurassic to the middle Cretaceous, frequently as apex predators. The evolution of pliosaurids during the later parts of the Early Cretaceous has recently been illuminated by discoveries from Russia (Hauterivian) and Colombia (Barremian). However, knowledge of pliosaurids representing the Jurassic–Cretaceous transition (late Tithonian – Valanginian), is still largely incomplete, especially during the earliest Cretaceous. As such, the effect on pliosaurids of hypothesized faunal turnover during the Jurassic–Cretaceous boundary interval is poorly understood. We report pliosaurid teeth from the upper Volgian (Tithonian, Upper Jurassic) of the Kheta river basin (Eastern Siberia, Russia), to the Berriasian and Valanginian (Lower Cretaceous) of the Volga region (European Russia). These assemblages have yielded a series of distinct tooth morphotypes, including the first reports of conical‐toothed pliosaurids from the latest Jurassic and earliest Cretaceous. This challenges the hypothesis that only one lineage of pliosaurids crossed the Jurassic–Cretaceous boundary. It appears that conical‐toothed pliosaurids co‐existed with their trihedral‐toothed relatives for at least 25 million years during the latest Jurassic and earliest Cretaceous. In fact, our quantitative analyses indicate that pliosaurids reached their maximal dental disparity during this interval, showing little evidence of turnover associated with the Jurassic–Cretaceous transition. Instead, disparity decreased later in the Early Cretaceous, with the disappearance of trihedral‐toothed forms in the Barremian.

During the Early–Late Cretaceous transition, marine ecosystems in Eurasia hosted a diverse set of large predatory reptiles that occupied various niches. However, most of our current knowledge of these animals is restricted to a small number of bonebed-like deposits. Little is known of the geographical and temporal extent of such associations. The middle Albian – middle Cenomanian phosphorite-bearing succession exposed at Annopol, Poland produces numerous ichthyosaurian and plesiosaurian fossils. These are mostly isolated skeletal elements (e.g. teeth, vertebrae), but disarticulated partial skeletons and an articulated, subvertically embedded ichthyosaur skull are also available. The following taxa are identified: ‘Platypterygius’ sp., cf. Ophthalmosaurinae, Ichthyosauria indet.,Polyptychodon interruptus, Pliosauridae indet., Elasmosauridae indet. and Plesiosauria indet. The large-sized ichthyosaur ‘Platypterygius’ and the pliosauridPolyptychodon interruptuspredominate within the upper Albian – middle Cenomanian deposits. The Annopol record, combined with data from England, France and western Russia, suggests that ‘Platypterygius’ andPolyptychodon interruptusformed a long-term, stable ecological sympatry in marine ecosystems of the European archipelago, at least during the Albian – middle Cenomanian. In addition, the marine reptile assemblage from Annopol is distinct from other Eurasian ecosystems in containing also elasmosaurids in its Albian portion.

Pliosaurus patagonicus sp. nov., from the middle Tithonian, Vaca Muerta Formation, Neuquén Province, Argentina, is described on an autapomorphic trait –i.e., the distance between the posterior functional alveolus and coronoid eminence (300 mm) equivalent to the last fourteen alveoli– and a unique combination of characters: short and robust mandibular symphysis with six pairs of functional alveoli; in lateral view the dorsoventral height is almost constant along the symphysis; low coronoid eminence and mandibular rami almost straight. As in other species of Pliosaurus genus the new taxon has trihedral teeth but the typical lateral expansion of the mandibular symphysis is missing. This new record reinforces the hypothesis of a trend toward the shortening of the mandibular symphysis observed in late Kimmeridgian–Tithonian species from the northern hemisphere. The presence of the macropredator Pliosaurus patagonicus sp. nov. in a protected marine environment close to the coast may be interpreted as the result of predatory and/or reproductive behaviors. Se describe una nueva especie de pliosáurido, Pliosaurus patagonicus sp. nov. del Titoniano medio de la Formación Vaca Muerta, Provincia de Neuquén, Argentina. La nueva especie se caracteriza por una autapomorfía, como es la distancia entre los últimos alvéolos posteriores y la eminencia coronoidea (300 mm) equivalente a los últimos catorce alvéolo, y la siguiente combinación de caracteres: sínfisis mandibular robusta y corta con seis alvéolos para dientes funcionales, altura de la sínfisis mandibular casi constante, eminencia coronoidea baja y ramas mandibulares casi rectas. Como en otras especies del género Pliosaurus, el nuevo taxón presenta dientes trihédricos pero el margen labial de la sínfisis carece de expansión lateral. Este registro refuerza la tendencia al acortamiento de la sínfisis mandibular observada en los Pliosaurus del hemisferio norte hacia el Kimmeridgiano–Titoniano. La presencia de un macrodepredador como Pliosaurus patagonicus sp. nov. en un ambiente marino protegido puede ser interpretada como consecuencia de un comportamiento predatorio y/o reproductivo. Fil: Brandoni, Zulma Nelida. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: O'gorman, Jose Patricio. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The Eulert pliosaurid remains (FHSM VP-321) housed at the Sternberg Museum of Natural History (Kansas, U.S.A.) include one of the world's best examples of a Cretaceous pliosaurid plesiosaur skull. The specimen's original assignment to Brachauchenius lucasi was based solely upon the skull (dorsal surface) and left lower jaw (lateral view) because the specimen was embedded in a plaster mount. The history of B. lucasi is similarly problematic, because the type and a referred skull were formerly visible only in ventral and dorsal views, respectively. Further preparation and comparison of these specimens reveal new data about the arrangement of cranial elements. The Eulert pliosaurid bears several distinct autapomorphies as compared with B. Lucasi, including cranial proportions (pretemporal length of palate longer, shorter temporal fenestrae), configuration of skull roof elements (frontals participate in premaxilla-parietal suture, suture occurs further forward), and configuration of the palate (poste...

The site of Goulmima (south Morocco) is well known for its rich marine fauna of Turonian age (Late Cretaceous). It has yielded a large variety of invertebrates but also of vertebrate taxa, represented by actinopterygians and marine reptiles including Plesiosauria (Sauropterygia) and Mosasauroidea (Squamata). The Plesiosauria are known so far by two major clades of Plesiosauroidea: the Elasmosauridae (Libonectes atlasenseBuchy, 2005) and the Polycotylidae (Thililua longicollis, Bardet, Suberbiola & Jalil, 2003a;Manemergus angirostrisBuchy, Metayer & Frey, 2005). Here we describe a new specimen of plesiosaur found in the same outcrop, differing from those previously cited and belonging to the other large plesiosaur clade, the Pliosauroidea. Comparison of this specimen with other Plesiosauria shows that it belongs toBrachauchenius lucasiWilliston (1903), a species previously known only from the Cenomanian–Turonian stages of the Western Interior Seaway of North America and in the upper Barremian succession of northern South America (Colombia). The description of this species on a contemporaneous site of North Africa significantly expands its palaeobiogeographic distribution. This discovery confirms the affinities between marine faunas of the Western Interior Seaway and those of North Africa at this time, and also permits a better understanding of the palaeobiology of the Goulmima outcrop. A discussion about the systematical status ofPolyptychodonOwen, 1841 is also provided.

An almost complete, three-dimensionally preserved plesiosaurian from the Hildoceras bifrons Zone of the Alum Shale Member (Whitby Limestone Formation; Lower Toarcian) of Yorkshire, UK, is described in detail. This represents a new species of Hauffiosaurus, H. tomistomimus, distinguished from H. zanoni (Harpoceras serpentinum Zone, Lower Toarcian, Germany) by the proportionally shorter neck and strongly concave preaxial margin of the tibia. It differs from H. longirostris (previously ‘Macroplata’ longirostris; Har. serpentinum Zone, Yorkshire) by the absence of prominent midline ridges on the dorsal surface of the premaxillae and ventral surface of the mandibular symphysis, and the absence of midline pterygoid contact ventral to the basioccipital. Several synapomorphies support a monophyletic Hauffiosaurus: broad longitudinal troughs occupy the dorsolateral surface of the maxilla and the posterior half of the lateral surface of the dentary; basicranial fontanelle bounded laterally by posterolaterally elongate projections of an undetermined ossification; and the neural arch contacts the rib facet in all postaxial cervical vertebrae. However, the systematic position of Hauffiosaurus, as a pliosauroid or basal plesiosauroid, remains uncertain. There is little evidence for geographic differentiation of Lower Toarcian plesiosaurian faunas in the United Kingdom and Germany as minor differences between abundant taxa may arise from temporal offset of fossils from these regions, and marked taxonomic differences are confined to rare taxa whose absence in one or other area may be attributable to incomplete sampling. Lack of consensus on the relationships of Lower Jurassic plesiosaurians requires further detailed description of Lower Jurassic taxa.

A partial pliosaur skull reveals anatomical features poorly known for Plesiosauria. The specimen lacks recorded contextual information, however preservational character and nannofossil analysis (earliest Turonian) suggests origination from the upper Greenhorn Limestone. The vomers bifurcate near their posterior termination, and are overlapped by long, slender extensions of the anterior pterygoids. The latter character has only recently been noted and may be variously developed in many if not all plesiosaurs. Large foramina commonly referred to as the ‘internal nares’ are formed at the juncture of the palatines, vomers, and maxillae. Configuration of the palatal elements differs in several ways from the only well established pliosaurid taxon of the North American Cretaceous, Brachauchenius. Particular differences include a more visibly elongate and lanceolate shape of the vomers, palatines which do not project as far anteriorly (similarly for the ‘internal nares’), and a squared posterior terminat...

Recent fieldwork in the Tropic Shale of southern Utah has resulted in the recovery of several specimens of short-necked plesiosaurs including both polycotylid plesiosauroids and pliosaurids. This report focuses on the former, whereas the latter are discussed in an accompanying paper. Although the Late Cretaceous Cenomanian/Turonian Stage boundary falls within the lower few meters of the Tropic Shale, all but one of the specimens were found in lower Turonian strata based on molluscan assemblages found in direct association with the skeletal material. The plesiosauroid family Polycotylidae is represented by at least three taxa: (1) the ‘typical’ late Cenomanian/early Turonian Trinacromerum; (2) Eopolycotylus rankini, gen. et sp. nov., a new genus and species that shares synapomorphies with the late Santonian/early Campanian Polycotylus latipinnus; and (3) Palmula quadratus, gen. et sp. nov., another new taxon that shares synapomorphies with unnamed taxa from the late Cenomanian of South Dakota and ...

Recent fieldwork in the Tropic Shale of southern Utah has resulted in the recovery of two new specimens of the short-necked pliosaurid Brachauchenius lucasi Williston, 1903. Both specimens were recovered in Lower Turonian strata a few meters above the Cenomanian-Turonian Stage boundary as determined from molluscan assemblages found in direct association, and both include skull material. The larger of the two also includes pectoral and pelvic elements previously unknown for this taxon. These specimens represent the first records of B. lucasi from the western margin of the Cretaceous Western Interior Seaway; previously recorded specimens were recovered in Kansas and Texas. The Cenomanian through middle Turonian temporal range of B. lucasi, in addition to its geographic range across the seaway, indicates that this taxon suffered few, if any, negative consequences as a result of global scale oceanographic events, including marine extinctions, that transpired during late Cenomanian-early Turonian time.

Marine reptile remains, represented by several fragmentary skeletons and isolated elements, are described from the Lower Cretaceous (Aptian) southern high latitude deposits (Doncaster Member, Wallumbilla Formation) of White Cliffs in southeastern Australia. The specimens are attributable to at least three families of plesiosaur (Elasmosauridae, Polycotylidae and Pliosauridae) and probably one family of ichthyosaur (Ophthalmosauridae). Polycotylid material from White Cliffs is amongst the oldest from anywhere in the world, and could point to an eastern Gondwanan origin for the group. Interestingly, the White Cliffs marine reptile fossils occur in association with palaeoclimatic indicators denoting seasonally very cold to near freezing conditions. This differs markedly from the climate regimes typically tolerated by modern aquatic reptiles but suggests that some Mesozoic taxa were able to cope with low temperature environments. Exactly what adaptations facilitated their survival is unknown. However, various strategies including elevated metabolic rates, rapid growth and/or seasonal migration/hibernation might have enabled their exploitation of cold water habitats along the southern coastal margin of the Australian Cretaceous epicontinental seaway.

‘Tarlo's Contention’, that a mandible possessing five to six large caniniform teeth characterizes Pliosaurus macromerus is explored and shown to rest on the assumption that only two morphologies of pliosaur mandibular symphysis exist in the Kimmeridge Clay Formation. A new taxon, Pliosaurus portentificus sp. nov., is described based on a third mandibular symphysial morphology from the Kimmeridge Clay near Ely, Cambridgeshire, UK. This specimen invalidates ‘Tarlo's Contention’, which was the basis for reassigning Stretosaurus macromerus (formerly Pliosaurus macromerus ) to the genus Liopleurodon . All material currently assigned to Liopleurodon macromerus should revert to the original combination of Pliosaurus macromerus Phillips, 1871 .

Marine reptile fossils are common in the Cretaceous epicontinental and continental-margin marine deposits of Australia but much of the material is sparsely documented. A review of current localities indicates that the majority of remains are known from the Aptian–Albian epicontinental marine units of the Eromanga Basin in Queensland, New South Wales and South Australia. Fragmentary specimens have also been recovered from Berriasian, Hauterivian–Barremian, Albian–Cenomanian, Cenomanian–Turonian and Maastrichtian marine deposits of Western Australia, Aptian or Albian continental margin rocks of the Northern Territory and Aptian–Albian freshwater sediments of New South Wales and Victoria. Interestingly, many of these deposits represent Cretaceous high latitude-polar environments and some include palaeoclimatic indicators suggesting very cold to near freezing conditions. As currently known, the Australian Cretaceous marine reptile fauna comprises one family of ichthyosaurs (Ophthalmosauridae), as many as five families of plesiosaur (Rhomaleosauridae, Pliosauridae, Polycotylidae, Elasmosauridae and possibly Cryptoclididae or Cimoliasauridae sensu Acta Zool. Fenn. 213 (2001)), one family of chelonioid sea turtle (Protostegidae) and indeterminate mosasaurids. Although few named Australian species may be regarded as valid, the stratigraphic distribution of taxa correlates well with that from elsewhere. Plesiosaurs and ichthyosaurs dominate Lower Cretaceous deposits with plesiosaurs showing a high taxonomic diversity (including the earliest known polycotylids), particularly in the Aptian. Albian faunas see the advent of chelonioid turtles with a corresponding reduction in plesiosaur diversity (through the loss of rhomaleosaurids) and a marked increase in the numbers of ichthyosaur remains. Upper Cretaceous units have produced only fragmentary specimens of primarily plesiosaurs and mosasaurs with ichthyosaurs limited to rocks of Cenomanian age.

The fragmentary remains of a plesiosaur have been collected from the Haida Formation (Albian, Lower Cretaceous) at Cumshewa Inlet, Queen Charlotte Islands, British Columbia. The specimen is identified as a member of the family Pliosauridae, based on tooth structure. This is the first record of a pliosaurid from the west coast of North America, and the first pliosaurid from the Lower Cretaceous of North America.

A new taxon of Cretaceous short-necked plesiosaur, Edgarosaurus muddi, gen. et sp. nov., is described. The specimen consists of a complete skull, 34 vertebrae including the entire series of 26 cervicale, and a nearly complete forelimb. The new taxon occurs in marine sediments of the Thermopolis Shale (late Albian), deposited during an early transgression of the Western Interior Seaway. The skull of Edgarosaurus is the oldest, and one of the best preserved plesiosaur specimens from the Cretaceous Western Interior of North America described to date. Edgarosarus differs from the morphologically and stratigraphically close short-necked taxon Plesiopleurodon wellesi in a number of cranial characters. In the absence of an established phylogenetic framework, the new plesiosaur is placed in the Polycotylidae, as recently defined by Carpenter in 1996. It is plesiomorphic with respect to other polycotylids in that it possesses a relatively robust and moderately elongated rostrum, a pineal foramen, caninifo...

A newly prepared plesiosaur skull collected by Thomas Hawkins (1810–1889) from the Lias quarries of Street, Somerset, England, provides important indications of character polarity within the Plesio...

Pliosaurids were a long-lived and cosmopolitan group of marine predators that spanned 110 million years and occupied the upper tiers of marine ecosystems from the Middle Jurassic until the early Late Cretaceous. A well-preserved giant pliosaurid skull from the Late Jurassic Kimmeridge Clay Formation of Dorset, United Kingdom, represents a new species, Pliosaurus kevani. This specimen is described in detail, and the taxonomy and systematics of Late Jurassic pliosaurids is revised. We name two additional new species, Pliosaurus carpenteri and Pliosaurus westburyensis, based on previously described relatively complete, well-preserved remains. Most or all Late Jurassic pliosaurids represent a globally distributed monophyletic group (the genus Pliosaurus, excluding ‘Pliosaurus’ andrewsi). Despite its high species diversity, and geographically widespread, temporally extensive occurrence, Pliosaurus shows relatively less morphological and ecological variation than is seen in earlier, multi-genus pliosaurid assemblages such as that of the Middle Jurassic Oxford Clay Formation. It also shows less ecological variation than the pliosaurid-like Cretaceous clade Polycotylidae. Species of Pliosaurus had robust skulls, large body sizes (with skull lengths of 1.7–2.1 metres), and trihedral or subtrihedral teeth suggesting macropredaceous habits. Our data support a trend of decreasing length of the mandibular symphysis through Late Jurassic time, as previously suggested. This may be correlated with increasing adaptation to feeding on large prey. Maximum body size of pliosaurids increased from their first appearance in the Early Jurassic until the Early Cretaceous (skull lengths up to 2360 mm). However, some reduction occurred before their final extinction in the early Late Cretaceous (skull lengths up to 1750 mm).

Incomplete reptile specimens from rocks of Piripauan-Haumurian age (Campanian-Maastrichtian), that represent the first records of elasmosaurs and pliosaurs from the North Island of New Zealand, are described. Present among the remains is the first elasmosaur cranial material (both adult and juvenile) known from New Zealand. This has been described as a new genus and species of elasmosaur, Tuarangisaurus keyesi. The first North Island record of Mauisaurus haasti is also described. Many specimens, only identifiable to Family, are described as they provide the first record of certain skeletal elements from New Zealand and good comparative material for future studies. The pliosaur remains, identifiable to Family only, provide better preserved material than has so far been known from the New Zealand fossil record.

If not having a sternum the Plesiosauria differ from the Crocodilia and from all the Lacertian orders of Reptiles. Serpents with limbs being as yet undiscovered, the only true Reptilia which admit of comparison with Plesiosaurs in the pectoral bones are the Chelonians. And even here, at first sight, the resemblance is not so evident as to command attention; for the shapes of the plastron-bones in embryonic Tortoises are more suggestive of the pectoral and pelvic girdles of Plesiosaurians than are the internal chelonian bones which support the limbs, since in Plesiosaurs these osteological elements are expanded shields which cover much of the abdominal surface. When, however, the embryonic pectoral arch of such a Chelonian as the Chelone mydas (fig. 1) is critically looked at, only unimportant osteological modification is needed to change its characters to those of a Plesiosaur. The chelonian coracoid bones ( c ) are rod-like; but their extension is entirely posterior to the articulation for the numeric: the bones approximate somewhat posteriorly, are somewhat concave on their outer margin, and terminate in cartilages of a shoe-shaped form, which are so extended inward that their toe-like terminations meet in the median line. Then, from the humeral articulation the two precoracoids ( pc ) extend inward towards the median line; they are inclined very slightly forward, and join either by their cartilages or intervening connective tissue. If, now, a line be drawn to join the median points of meeting of

We here describe the rostrum of a pliosaur from the Kimmeridgian of northeastern Mexico. The specimen comes from the Upper Jurassic La Casita Formation (Kimmeridgian - Tithonian) and represents one of the few Plesiosauria in the area. The internal anatomy of the specimen is partly visible through cross-sections, which reveal a hitherto undescribed rostral prolongation of a paired bone of the interorbital area, probably the parietal or frontal beneath the premaxillae. The specimen also provides new information on the morphology and function of the choanae. In light of these morphological data, the new pliosaur shows similarities both with the European Late Jurassic genus Pliosaurus and the Australian Early Cretaceous Kronosaurus.