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Our knowledge of marine reptiles of the Callovian age (Middle Jurassic) is majorly based on the collections from the Oxford Clay Formation of England, which yielded a diverse marine reptile fauna of plesiosaurians, ichthyosaurians, and thalattosuchians. However, outside of Western Europe, marine reptile remains of this age are poorly known. Here, we survey marine reptiles from the Callovian stage of European Russia. The fossils collected over more than a century from 28 localities are largely represented by isolated bones and teeth, although partial skeletons are also known. In addition to the previously described rhomaleosaurid and metriorhynchids, we identify pliosaurids of the genera Liopleurodon and Simolestes; cryptoclidid plesiosaurians, including Cryptoclidus eurymerus, Muraenosaurus sp., and cf. Tricleidus, and ophthalmosaurid ichthyosaurians, including the iconic Ophthalmosaurus icenicus. These findings expand the ranges of several Callovian marine reptile taxa far to the Eastern Europe, and support the exchange of marine reptile faunas between Western and Eastern European seas in the middle to late Callovian. However, some specimens from the lower Callovian of European Russia show differences from typical representatives of the middle Callovian Oxford Clay fauna, possibly representing the earlier stages of evolution of some of these marine reptiles not yet recorded in Western Europe or elsewhere. [ABSTRACT FROM AUTHOR]

Four isolated cervical vertebrae from the Kimmeridge Clay Formation (Upper Jurassic, Kimmeridgian) of Abingdon, Oxfordshire, England are identified as from a pliosaurid plesiosaurian sauropterygian on account of their shortness relative to width and height, their near platycoelous nature and the location of tall rib facets on the centrum body. They are noteworthy for their size, with a maximum width of 269 mm, maximum height of 222 mm and maximum length of 103 mm. Simple scaling and comparisons with cervical vertebrae of Mid Jurassic pliosaurs Peloneustes and Liopleurodon , and the Early Cretaceous Stenorhynchosaurus and Sachicasaurus suggest a total body length of between ~ 9.8 m and 14.4 m for the Abingdon Kimmeridge Clay pliosaur. Likely the true length was towards the higher end of this range. A genus and species cannot be confidently determined on the basis of the described material, but they likely belong to Pliosaurus sp. or a similar animal, for which a precise neck length is not known. We estimate a neck length of 0.77 m for Pliosaurus ? brachyspondylus based on the average cervical lengths provided for specimen CAMSM J.35991. [ABSTRACT FROM AUTHOR]

A recently prepared fragment of the anterior end of a snout comprising occluded upper and lower jaws of a juvenile individual of Stenorhynchosaurus munozi Páramo-Fonseca et al., 2016 (Plesiosauria, Pliosauridae) is described herein. The specimen was found in the 1990s at Sutamarchán (Boyacá, Colombia), in Barremian beds of the Arcillolitas abigarradas Member of the Paja Formation. Its description provides hitherto unknown valuable morphological information on the species: dorsal anterior extension of the vomer, five premaxillary teeth (not four as was previously suggested), and anteriorly directed orientation of the first premaxillary alveolus (procumbent). New observations made on previously studied material corroborated the existence of procumbent anterior premaxillary teeth in the species. The presence of this trait highlights the close relationship of S. munozi with other early-diverging brachauchenines from the Lower Cretaceous of Russia. [ABSTRACT FROM AUTHOR]

We describe the anatomy of a new longirostrine pliosaurid, Eardasaurus powelli gen. et sp. nov., based on a substantially complete skeleton from the Middle Jurassic Oxford Clay Formation of Oxfordshire, UK. The specimen brings the number of pliosaurid genera known from the Oxford Clay Formation up to a minimum of six, contributing to our understanding of the most taxonomically rich pliosaurid assemblage. The teeth of Eardasaurus powelli gen. et sp. nov. have “carina-like” apicobasal enamel ridges, previously only identified in Liopleurodon ferox among Middle Jurassic pliosaurids, and which may be more widespread among early pliosaurids than has been recognised. Our phylogenetic analysis shows that Eardasaurus powelli gen. et sp. nov. is nested within Middle Jurassic thalassophonean pliosaurids, slightly more derived than Peloneustes philarchus, as sister to a group comprising “Pliosaurus” andrewsi, Simolestes vorax, Liopleurodon ferox, Pliosaurus spp. and brachauchenines.

Marine reptiles from the Upper Jurassic of Central Europe are rare and often fragmentary, which hinders their precise taxonomic identification and their placement in a palaeobiogeographic context. Recent fieldwork in the Kimmeridgian of Krzyżanowice, Poland, a locality known from turtle remains originally discovered in the 1960s, has reportedly provided additional fossils thought to indicate the presence of a more diverse marine reptile assemblage, including giant pliosaurids, plesiosauroids, and thalattosuchians. Based on its taxonomic composition, the marine tetrapod fauna from Krzyżanowice was argued to represent part of the “Matyja-Wierzbowski Line”—a newly proposed palaeobiogeographic belt comprising faunal components transitional between those of the Boreal and Mediterranean marine provinces. Here, we provide a detailed re-description of the marine reptile material from Krzyżanowice and reassess its taxonomy. The turtle remains are proposed to represent a “plesiochelyid” thalassochelydian (Craspedochelys? sp.) and the plesiosauroid vertebral centrum likely belongs to a cryptoclidid. However, qualitative assessment and quantitative analysis of the jaws originally referred to the colossal pliosaurid Pliosaurus clearly demonstrate a metriorhynchid thalattosuchian affinity. Furthermore, these metriorhynchid jaws were likely found at a different, currently indeterminate, locality. A tooth crown previously identified as belonging to the thalattosuchian Machimosaurus is here considered to represent an indeterminate vertebrate. The revised taxonomy of the marine reptiles from Krzyżanowice, as well as the uncertain provenance of the metriorhynchid specimen reported from the locality, cast doubt on the palaeobiogeographic significance of the assemblage.

We describe the anatomy of a new longirostrine pliosaurid, Eardasaurus powelli gen. et sp. nov., based on a substantially complete skeleton from the Middle Jurassic Oxford Clay Formation of Oxfordshire, UK. The specimen brings the number of pliosaurid genera known from the Oxford Clay Formation up to a minimum of six, contributing to our understanding of the most taxonomically rich pliosaurid assemblage. The teeth of Eardasaurus powelli gen. et sp. nov. have "carina-like" apicobasal enamel ridges, previously only identified in Liopleurodon ferox among Middle Jurassic pliosaurids, and which may be more widespread among early pliosaurids than has been recognised. Our phylogenetic analysis shows that Eardasaurus powelli gen. et sp. nov. is nested within Middle Jurassic thalassophonean pliosaurids, slightly more derived than Peloneustes philarchus, as sister to a group comprising "Pliosaurus" andrewsi, Simolestes vorax, Liopleurodon ferox, Pliosaurus spp. and brachauchenines. [ABSTRACT FROM AUTHOR]

Ischyrodon meriani is an obscure pliosaurid taxon established upon an exceptionally large tooth crown of a probable Callovian (Middle Jurassic) age that originates from Wölflinswil, Canton of Aargau, Switzerland. Despite being known for almost two centuries, the specimen remains poorly researched. Historically, I. meriani has been associated, or even considered conspecific, with Pliosaurus macromerus and Liopleurodon ferox. However, neither of the two hypotheses have been tested through detailed comparisons or using modern quantitative methods. Here, we redescribe the type of Ischyrodon meriani, illustrate it, and compare to teeth of thalassophonean pliosaurids, with special focus on Jurassic representatives of the clade. Multivariate analyses show close similarities to L. ferox but comparable structures to those of I. meriani, including a distinctive pattern of the apicobasal ridges, are also observable in some mid-Cretaceous brachauchenines from the 'Polyptychodon' assemblage of East and South East England. While it is likely that I. meriani represents a Liopleurodonlike taxon, or is indeed conspecific with L. ferox, which would make I. meriani the proper name for the species, any such taxonomic considerations are hindered by the fragmentary nature of the type specimens of both these taxa as well as limited knowledge of the dental variability within and between individual jaws of L. ferox. Currently, I. meriani is best treated as a nomen dubium. Finally, we discuss the potential implications of I. meriani being conspecific with L. ferox, and additionally provide a commentary on the taxonomic status of Liopleurodon. [ABSTRACT FROM AUTHOR]

Ischyrodon meriani is an obscure pliosaurid taxon established upon an exceptionally large tooth crown of a probable Callovian (Middle Jurassic) age that originates from Wölflinswil, Canton of Aargau, Switzerland. Despite being known for almost two centuries, the specimen remains poorly researched. Historically, I. meriani has been associated, or even considered conspecific, with Pliosaurus macromerus and Liopleurodon ferox. However, neither of the two hypotheses have been tested through detailed comparisons or using modern quantitative methods. Here, we redescribe the type of Ischyrodon meriani, illustrate it, and compare to teeth of thalassophonean pliosaurids, with special focus on Jurassic representatives of the clade. Multivariate analyses show close similarities to L. ferox but comparable structures to those of I. meriani, including a distinctive pattern of the apicobasal ridges, are also observable in some mid-Cretaceous brachauchenines from the ‘Polyptychodon’ assemblage of East and South East England. While it is likely that I. meriani represents a Liopleurodon-like taxon, or is indeed conspecific with L. ferox, which would make I. meriani the proper name for the species, any such taxonomic considerations are hindered by the fragmentary nature of the type specimens of both these taxa as well as limited knowledge of the dental variability within and between individual jaws of L. ferox. Currently, I. meriani is best treated as a nomen dubium. Finally, we discuss the potential implications of I. meriani being conspecific with L. ferox, and additionally provide a commentary on the taxonomic status of Liopleurodon.

Pliosaurids were the dominant macropredators in aquatic environments at least since the Middle Jurassic until their extinction in the early Late Cretaceous. Until very recently, the Cretaceous record of Pliosauridae has been poor and difficult to interpret from the taxonomic and phylogenetic perspective. Despite that the knowledge of Cretaceous pliosaurids improved in recent years, numerous aspects of their evolutionary history still remain only poorly known. Here, we report the first pliosaurid material from Venezuela. The taxon is most likely earliest Cenomanian in age, thus representing the youngest occurrence of Pliosauridae from South America. The Venezuelan taxon is based on a well-preserved tooth crown whose morphology and outer enamel structural elements appear to resemble especially those observable in the giant pliosaurid Sachicasaurus vitae from the Lower Cretaceous of Colombia. The new discovery extends the pliosaurid record on the continent by more than 10 million years and likely marks the southernmost Upper Cretaceous occurrence of Pliosauridae, worldwide. We also briefly discuss the affinities of the enigmatic Venezuelan elasmosaurid Alzadasaurus tropicus and highlight similarities to elasmosaurids from the Western Interior Seaway. [ABSTRACT FROM AUTHOR]

Marine reptiles from the Upper Jurassic of Central Europe are rare and often fragmentary, which hinders their precise taxonomic identification and their placement in a palaeobiogeographic context. Recent fieldwork in the Kimmeridgian of Krzyżanowice, Poland, a locality known from turtle remains originally discovered in the 1960s, has reportedly provided additional fossils thought to indicate the presence of a more diverse marine reptile assemblage, including giant pliosaurids, plesiosauroids, and thalattosuchians. Based on its taxonomic composition, the marine tetrapod fauna from Krzyżanowice was argued to represent part of the "Matyja-Wierzbowski Line"--a newly proposed palaeobiogeographic belt comprising faunal components transitional between those of the Boreal and Mediterranean marine provinces. Here, we provide a detailed re-description of the marine reptile material from Krzyżanowice and reassess its taxonomy. The turtle remains are proposed to represent a "plesiochelyid" thalassochelydian (Craspedochelys? sp.) and the plesiosauroid vertebral centrum likely belongs to a cryptoclidid. However, qualitative assessment and quantitative analysis of the jaws originally referred to the colossal pliosaurid Pliosaurus clearly demonstrate a metriorhynchid thalattosuchian affinity. Furthermore, these metriorhynchid jaws were likely found at a different, currently indeterminate, locality. A tooth crown previously identified as belonging to the thalattosuchian Machimosaurus is here considered to represent an indeterminate vertebrate. The revised taxonomy of the marine reptiles from Krzyżanowice, as well as the uncertain provenance of the metriorhynchid specimen reported from the locality, cast doubt on the palaeobiogeographic significance of the assemblage. [ABSTRACT FROM AUTHOR]

A new fossil MP111209-1 found in the Barremian beds of Sáchica, a town near Villa de Leiva representing the more complete skeleton found in the region is described here. After a detailed study of its morphological characteristics, it is evident that the new specimen represents a new genus and species of brachauchenine pliosaurid from Central Colombia that we named Sachicasaurus vitae gen. et sp. nov. Sachicasaurus is a large brachauchenine (almost 10 m in length) characterized by the following combination of characters: skull exceeding two meters in length, transverse constriction in the rostrum, caniniform teeth present, pineal foramen in a very advanced position, palatines separated in the midline by the pterygoids, very short mandibular symphysis (bearing four teeth positions), reduced number of mandibular teeth (less than 20), slender hyoid bones, 12 cervical vertebrae, cervical centra showing ventral foramina, single rib facet in all cervical centra, at least 40 pre-caudal vertebrae, and ilium with a long posterior projection. Although it is difficult to clearly establish the phylogenetic position of Sachicasaurus viate within Brachaucheninae due to its combination of primitive and derived features, the morphological comparisons and the cladistic analysis show an evident phylogenetic proximity of Sachicasaurus to the Aptian-Albian genus Kronosaurus.

Here, we describe part of a large-bodied macrophagous plesiosaur jaw from the lower Bajocian (Middle Jurassic) Passwang Formation near Arisdorf in the Basel-Land canton of Switzerland. The specimen preserves the posterior glenoid extremity of the right mandibular ramus comprising the surangular, angular, articular, and probably the prearticular. Notable character states include a transversely expanded surangular that incorporates a prominent medial ridge adjacent to the glenoid and a shallow dorsal fossa, together with a conspicuous trough extending across the lateral surfaces of both the surangular and angular; there is also a basally broad and medially deflected retroarticular process. Collectively, these features suggest affinities with Middle–Late Jurassic pliosaurids, as well as some coeval rhomaleosaurids. Based on such comparisons, we estimate that the Passwang Formation mandible was approximately 1.5 m long when complete, and thus approaches the size range of the largest-known pliosaurids. This discovery supplements the sparse record of diagnostic pliosaurid-like remains from Switzerland and contributes to the currently incomplete knowledge of pre-Callovian Middle Jurassic plesiosaurs globally. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A new pliosaurid specimen found in the Barremian beds of Sáchica, a town near Villa de Leiva, representing the more complete skeleton found in the region is described here. After a detailed study of its morphological characteristics, it is evident that the new specimen represents a new genus and species of brachauchenine pliosaurid from Central Colombia that we name Sachicasaurus vitae gen. et sp. nov. Sachicasaurus is a large derived brachauchenine (almost 10 m in length) characterized by two autopomorphic characters: a very short mandibular symphysis ending at the mid length of the fourth mandibular alveoli and reduced number of mandibular teeth (17-18). It is also distinguished by the following combination of characters: skull exceeding two meters in length, lateral expansion of the maxilla posterior to the premaxilla-maxilla suture, presence of caniniform teeth, dental sequence showing only two noncontiguous largest teeth (D4, Mx1), pineal foramen in a very anterior position, vomer bifurcated posteriorly, palatines separated in the midline by the pterygoids, slender hyoid bones, 12 cervical vertebrae, cervical centra without dorsal but with ventral foramina, single rib facet in all cervical centra, at least 37 pre-sacral vertebrae, and ilium with a long posterior projection. The morphological comparisons and the cladistic analysis show the new specimen as a derived brachauchenine with evident phylogenetic proximity to the Colombian species "Kronosaurus" boyacensis from the upper Aptian, suggesting that they could belong to the same genus. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Pliosauridae is a globally distributed clade of aquatic predatory amniotes whose fossil record spans from the Lower Jurassic to the Upper Cretaceous. However, the knowledge of pliosaurid interrelationships remains limited. In part, this is a consequence of a few key taxa awaiting detailed reassessment. Among them, the taxon Polyptychodon is of special importance. It was established on isolated teeth from the mid-Cretaceous strata of East and South East England and subsequently associated with numerous finds of near-cosmopolitan distribution. Here the taxon is reassessed based on the original dental material from England, with special focus on a large collection of late Albian material from the Cambridge Greensand near Cambridge. The dental material is reviewed here from historical and stratigraphic perspective, described in detail, and discussed in terms of its diagnostic nature. The considerable morphological variability observed in the teeth attributed to Polyptychodon, together with a wide stratigraphic range of the ascribed material, possibly exceeding 35 Ma (early Aptian to ?middle Santonian), suggests that the taxon is based on a multispecies assemblage, possibly incorporating members of different plesiosaur clades. Due to the absence of any autapomorphic characters or unique character combinations in the original material, Polyptychodon interruptus, the type species of Polyptychodon, is considered nomen dubium. From a global perspective, Polyptychodon is viewed as a wastebasket taxon whose material originating from different localities should be reconsidered separately.

Dental morphology and patterns of tooth replacement in representatives of the clade Pliosauridae (Reptilia, Sauropterygia) are evaluated in detail. The jaws of one basal (Thalassiodracon hawkinsii) and two derived species (Pliosaurus carpenteri, Pliosaurus kevani) were visualized by μCT scans, and the ontogenetic patterns, or ‘movement paths’, of replacement teeth could be mapped. Other specimens (Peloneustes philarchus and Pliosaurus westbuyensis) with well-preserved jaws containing functional and replacement teeth in situ were also examined directly, and waves of tooth replacement could be inferred from the degree of in situ tooth development and the fusion between functional and replacement alveoli. The analysis revealed symmetrical tooth eruption over the medial axis throughout the length of the jaw in the basal pliosaurid Thalassiodracon. By contrast, symmetrical tooth eruption patterns occur only along the anterior sections of the jaws of derived pliosaurids. In Pliosaurus, replacement schedules differ in the anterior and posterior portions of the jaws and appear to correlate with differences in tooth morphology and symmetrical replacement. The anterior teeth exhibit longer replacement cycle periods and symmetrical replacement, while shorter cycle periods and asymmetry are seen posteriorly. A longer period suggests slower replacement and is characteristic of large, specialized caniniform teeth in the longer snouted Late Jurassic taxa. Smaller posterior teeth have a shorter period and therefore a faster replacement cycle. The transition from long to short replacement period over the length of the jaw is thought to account for the loss of symmetry. This differentiation could relate to differential tooth function and a type of heterodonty. We therefore propose a new model of pliosaurid tooth replacement patterns and present it in a phylogenetic context.

During the Middle and Late Jurassic, pliosaurid plesiosaurs evolved gigantic body size and a series of craniodental adaptations that have been linked to the occupation of an apex predator niche. Cretaceous pliosaurids (i.e. Brachaucheninae) depart from this morphology, being slightly smaller and lacking the macrophagous adaptations seen in earlier forms. However, the fossil record of Early Cretaceous pliosaurids is poor, concealing the evolution and ecological diversity of the group. Here, we report a new pliosaurid from the Late Hauterivian (Early Cretaceous) of Russia. Phylogenetic analyses using reduced consensus methods recover it as the basalmost brachauchenine. This pliosaurid is smaller than other derived pliosaurids, has tooth alveoli clustered in pairs and possesses trihedral teeth with complex serrated carinae. Maximum-likelihood ancestral state reconstruction suggests early brachauchenines retained trihedral teeth from their ancestors, but modified this feature in a unique way, convergent with macrophagous archosaurs or sphenacodontoids. Our findings indicate that Early Cretaceous marine reptile teeth with serrated carinae cannot be unequivocally assigned to metriorhynchoid crocodylomorphs. Furthermore, they extend the known diversity of dental adaptations seen in Sauropterygia, the longest lived clade of marine tetrapods.

The fossil record of metriorhynchids and plesiosaurians from the Rosso Ammonitico Veronese Formation (RAVFm, Middle–Upper Jurassic, Italy) is represented by elements collected between the eighteenth and twentieth centuries. All the metriorhynchid material is referred to the genusNeptunidraco. The first RAVFm plesiosaurian material was collected in the nineteenth century and referred toPlesiosaurus: elements are here described and interpreted as a chimerical association of crocodylomorph and plesiosaurian bones, providing the first co-occurrence of these clades in the RAVFm. The second plesiosaurian is the associated skeleton that we refer toAnguanax zignoigen. et sp. nov. Bayesian phylogenetic analysis confirms the basal geosaurine affinities ofNeptunidracoresulted by parsimony analysis. Using both methods,Anguanaxwas recovered as a basal pliosaurid, sister group of the clade includingMarmornectesand Thalassophonea. Bayesian inference methods indicate that both Italian lineages diverged from other known lineages between 176 and 171 Mya, also showing divergence rates significantly higher than any other representative of their respective clades. We suggest a phase of rapid evolutionary adaptation to deeper marine environments in the ancestors of the Rosso Ammonitico Veronese reptiles as a response to the latest Liassic regressive regime in Northern Tethys. [ABSTRACT FROM PUBLISHER]

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 atlasense Buchy, 2005) and the Polycotylidae (Thililua longicollis, Bardet, Suberbiola & Jalil, 2003a; Manemergus angirostris Buchy, 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 to Brachauchenius lucasi Williston (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 of Polyptychodon Owen, 1841 is also provided. [ABSTRACT FROM AUTHOR]

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Plesiosauria is a clade of medium to large bodied marine reptiles with a cosmopolitan distribution ranging from the latest Triassic to the end of the Cretaceous. In Europe, the fossil record of Plesiosauria is mainly known from the Northern latitudes, whereas it is much rarer from the Southern and Mediterranean areas. Here, we report the first articulated skeleton of an Italian plesiosaurian, from the Callovian--Oxfordian deposits of the Rosso Ammonitico Veronese Formation of Kaberlaba (Veneto). The specimen is referred to Pliosauridae based on the large size of the skull, compared to the appendicular skeleton, the presence of the lacrimal, and a distinct anterolateral projection of the prefrontal into the orbital margin. Mandibular and vertebral symplesiomorphies support the placement of the Italian taxon among the "gracile-lonirostrine grade" of basal pliosaurids. The Kaberlaba plesiosaurian represents the second reptile clade recovered from the Rosso Ammonitico Veronese Formation, after Thalattosuchia. [ABSTRACT FROM AUTHOR]

Pliosaurs were among the largest predators in Mesozoic seas, and yet their functional anatomy and feeding biomechanics are poorly understood. A new, well-preserved pliosaur from the Kimmeridgian of Weymouth Bay ( UK) revealed cranial adaptations related to feeding. Digital modelling of computed tomography scans allowed reconstruction of missing, distorted regions of the skull and of the adductor musculature, which indicated high bite forces. Size-corrected beam theory modelling showed that the snout was poorly optimised against bending and torsional stresses compared with other aquatic and terrestrial predators, suggesting that pliosaurs did not twist or shake their prey during feeding and that seizing was better performed with post-symphyseal bites. Finite element analysis identified biting-induced stress patterns in both the rostrum and lower jaws, highlighting weak areas in the rostral maxillary-premaxillary contact and the caudal mandibular symphysis. A comparatively weak skull coupled with musculature that was able to produce high forces, is explained as a trade-off between agility, hydrodynamics and strength. In the Kimmeridgian ecosystem, we conclude that Late Jurassic pliosaurs were generalist predators at the top of the food chain, able to prey on reptiles and fishes up to half their own length. [ABSTRACT FROM AUTHOR]

Complete plesiosaur skeletons are relatively abundant in the Lower Jurassic of England and Germany, but are exceptional in France. A new specimen from Normandy (northern France), including incomplete skull, palate and mandible with several associated vertebrae, is here described and its pliosauroid affinities are discussed. Comparison of this new specimen with other plesiosaurians indicates that it belongs to a new genus and species: Cryonectes neustriacus. This new plesiosaurian taxon represents one of the most complete pliosaurids reported from the Pliensbachian, a stage that has yielded very few diagnostic plesiosaurian remains. Our preliminary phylogenetic analysis places Cryonectes in a basal position among Pliosauridae, and suggests that the radiation of this clade occurred several millions of years earlier than previously thought. This new taxon contributes to our understanding of Early Jurassic plesiosaur diversity. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

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 toBrachauchenius lucasiwas based solely upon the skull (dorsal surface) and left lower jaw (lateral view) because the specimen was embedded in a plaster mount. The history ofB. lucasiis 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 withB. 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 (posterior vomers not masked by medial alar extensions of the palatines, caudal vomerian fenestrae positioned further posterior, long slit-like anterior pteryoid vacuity present). Furthermore, FHSM VP-321 possesses double-headed cervical ribs, a feature previously unknown in Cretaceous pliosaurids. This combination of characters merits separation of the Eulert pliosaurid and a referred specimen to a new taxon,Megacephalosaurus eulerti. The type and paratype skulls ofM. eulertiare 1.5 m and 1.75 m in length, respectively, and thus 50% and 75% larger than the known 1-m-long skulls ofB. lucasi, suggesting thatM. eulertimay attain larger size thanB. lucasi. [ABSTRACT FROM PUBLISHER]

Complete skulls of giant marine reptiles of the Late Jurassic are rare, and so the discovery of the 1.8-m-long skull of a pliosaur from the Kimmeridge Clay Formation (Kimmeridgian) of Westbury, Wiltshire, UK, is an important find. The specimen shows most of the cranial and mandibular anatomy, as well as a series of pathological conditions. It was previously referred to Pliosaurus brachyspondylus, but it can be referred reliably only to the genus Pliosaurus, because species within the genus are currently in need of review. The new specimen, together with another from the same locality, also referred to P. brachyspondylus, will be crucial in that systematic revision, and it is likely that the genus Pliosaurus will be found to include several genera. The two Westbury Pliosaurus specimens share many features, including the form of the teeth, but marked differences in the snout and parietal crest suggest sexual dimorphism; the present specimen is probably female. The large size of the animal, the extent of sutural fusion and the pathologies suggest this is an ageing individual. An erosive arthrotic condition of the articular glenoids led to prolonged jaw misalignment, generating a suite of associated bone and dental pathologies. Further damage to the jaw joint may have been the cause of death. [ABSTRACT FROM AUTHOR]

Peloneustes philarchus is the most abundant pliosaurid from the Peterborough Member of the Oxford Clay Formation (Callovian) of the UK. It is a valid taxon possessing a unique character combination, including a single autapomorphy: the interdentary symphysis is raised dorsally on a narrow platform. Twenty-one specimens can be positively referred to P. philarchus. However, other specimens previously referred to Peloneustes, from the Peterborough Member near Peterborough, and the lower Oxfordian strata of Marquise, northern France, represent distinct, unnamed taxa. The skull of P. philarchus is described in detail, including new information from an uncrushed, three-dimensionally preserved specimen and a specimen with a well-preserved palate. Well-preserved material clearly indicates that P. philarchus lacked nasals, but possessed a lacrimal. A previously unrecognised 'palpebral' forms part of the dorsal orbit margin adjacent to the prefrontal. The number of maxillary (30-31) and dentary (36-44) alveoli, the number of dentary alveoli adjacent to the mandibular symphysis (13-15), the number of foramina on the frontal and jugal, the breadth of the parasphenoid, breadth of the anterior (narial) process of the palatine and the presence of a lappet of the angular that extends onto the posterodorsal surface of the retroarticular process vary among individuals but are not considered sufficient to justify the recognition of new taxa. The presence of an open palpebral-prefrontal suture, the size of the ventral midline tubercle of the basioccipital and the presence of an anterior interpterygoid vacuity seem to vary with body size. [ABSTRACT FROM AUTHOR]

The exquisitely preserved holotype of the pliosaur ' Rhomaleosaurus' victor (SMNS 12478) is described from the Toarcian Posidonien-Schiefer (Upper Lias, Lower Jurassic) of Holzmaden (Baden-Württemberg), Germany. The specimen presents a novel combination of synapomorphies and unique morphometric proportions separating it from Rhomaleosaurus sensu stricto and warranting the erection of a new genus, Meyerasaurus gen. nov . Historically, the name 'Thaumatosaurus' has been interchangeable with Rhomaleosaurus and is frequently associated with SMNS 12478 in the literature. However, this is an invalid taxon and cannot be reinstated. The anatomy of Meyerasaurus victor is compared in detail with other pliosaurs, and its taxonomic affinity is reviewed. M. victor belongs to the family Rhomaleosauridae and shares several anatomical characters with Rhomaleosaurus including a short and robust premaxillary rostrum (length-to-width ratio c. 1.0), parallel premaxilla-maxilla sutures anterior to the nares, vomers contacting the maxillae posterior to the internal nares, and c. 28 cervical vertebrae minus the atlas-axis. The known geographical distribution of Rhomaleosaurus, which previously extended across the German and English palaeobiogeographical zones, is reduced to the English zone as a consequence of the referral of SMNS 12478 to a new genus. This is significant because it contributes to an ongoing trend of increasing generic separation between the German and English zones, while increasing the generic diversity within the German zone itself. [ABSTRACT FROM AUTHOR]

A new pliosaurid, Gallardosaurus iturraldei gen nov. et sp. nov., was found in the Viñales area, western Cuba, in sediments of the Jagua Formation, middle–late Oxfordian. This new taxon is characterized by: wide participation of the premaxilla in the outer margin of the external naris; frontal not participating in the orbital margin; postorbital in contact with the jugal and squamosal; presence of anterior pterygoid vacuity; cultriform process of parasphenoid convex and exposed in palatal view; pterygoid flanges high; jaw articulation low relative to tooth row; trihedral teeth in cross-section and with smooth ridges at least in the labial face. A phylogenetic analysis suggests that Gallardosaurus forms a clade with Peloneustes, the most common pliosaurid genus occurring in the Oxford Clay. The Caribbean Seaway was, at least since the Oxfordian, a corridor that permitted the interchange for marine biota between Western Tethys and Eastern Pacific realms. Among vertebrates, bony fish and long-necked plesiosaurs prevailed. However, marine pleurodiran turtles, metriorhynchid crocodilians, ophthalmosaurian ichthyosaurs, and pliosaurids ( G. iturraldei gen. nov. et sp. nov.) have also been found, as well as at least two species of pterosaurs, and one camarasaurian dinosaur. Among these reptiles there were off-shore pelagic forms such as the ichthyosaurs and metriorhynchids, together with the pliosaurid G. iturraldei gen. nov. et sp. nov.; other taxa were presumably less pelagic, such as the pleurodiran turtles and the cryptoclidid plesiosauroids. Gallardosaurus iturraldei gen. nov. et sp. nov. would have played the role of an active predator taking advantage of nectonic fish recorded in the area. [ABSTRACT FROM AUTHOR]

A partial skeleton of a plesiosaur (Reptilia: Sauropterygia) from the Hiccles Cove Formation (Middle Jurassic: Callovian) of Melville Island, Canadian Arctic Archipelago, is the first marine reptile fossil with well-preserved skull from the Canadian Arctic and represents a new genus and species of Rhomaleosauridae (Borealonectes russelli). The Rhomaleosauridae are a problematic group, and a review of the current status of included taxa is given prior to the description of the Canadian material. The holotype and only known specimen of the new species consists of the skull, anterior cervicals, and right forelimb. The new taxon is characterized by the large prefrontal and the configuration of the postorbital bar in which the postfrontal is excluded from the supratemporal fenestra; these are potentially unique features among rhomaleosaurids. It exhibits a combination of primitive and derived characteristics that are variable among rhomaleosaurids, such as the absence of the dorsomedian foramen and anterior pterygoid vacuity on the palate, and the presence of straight shaft of humerus. The occurrence of this specimen suggests a global distribution of rhomaleosaurids, and it is also significant as one of the few Jurassic plesiosaurs known from North America. [ABSTRACT FROM AUTHOR]

A partial skeleton tentatively referred to the Lower Cretaceous pliosauroid genus Leptocleidus is described from predominantly Aptian (Lower Cretaceous) opal-bearing deposits of the Bulldog Shale near Andamooka in South Australia. Small size coupled with incomplete fusion of the basicranial elements, vertebral centra, neural arches and cervical ribs, and incomplete ossification of the articular surfaces on the propodials and distal limb bones, indicate that the specimen was at an early stage in its ontogeny. Comparison with more mature specimens attributed to Leptocleidus spp. highlights several growth-related differences, particularly a marked disparity in proportions of the humerus and femur relative to the estimated maximum body length. Changes in the cranial skeleton during growth are harder to document because of the fragmentary nature of the skull. Nevertheless, fusion of some cranial sutures and well-developed cranial joint surfaces suggest that extensive ossification may have taken place in parts of the skull during early ontogeny. The potential implications of these findings for feeding, locomotion, and behavior in juvenile plesiosaurs are discussed. [ABSTRACT FROM AUTHOR]

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. [Copyright &y& Elsevier]

Pliosaurid plesiosaurs were among the largest predators of Mesozoic marine ecosystems attaining giant sizes up to 10–11 m in length, near a quarter of which could be constituted by a massive head. The known Late Cretaceous pliosaurids are comparatively smaller than the stratigraphically older taxa and lack a suite of macropredaceous features, demonstrating a somewhat decline of the group members towards their extinction in the Turonian. However, the early Late Cretaceous (Cenomanian) record of pliosaurids is scarce and mostly represented by isolated teeth, thus hampering the recognition of diversity and disparity of pliosaurids in this time interval. Here we describe a very large isolated cervical centrum (19 cm in maximum diameter) belonging to a brachauchenine pliosaurid. The comparison with other pliosaurids indicates that the centrum belonged to one of the largest known pliosaurids, comparable in size to Kronosaurus queenslandicus, ' Kronosaurus ' boyacensis and Sachicasaurus vitae from the Aptian–Albian of Australia and Barremian–Aptian of Colombia. This finding indicates that gigantic pliosaurids were also present in the Cenomanian. Thus, the previously inferred decrease in size of pliosaurids in the Late Cretaceous is likely a result of sampling bias, and, if present, it happened not earlier than in the late Cenomanian–Turonian, right before the extinction of the group. [ABSTRACT FROM AUTHOR]