Marine Reptiles

From one of the most complete Lower Cretaceous rock sequences in the world (in Villa de Leiva region, central Colombia), we describe a new genus and species of pliosaurid plesiosaur Stenorhynchosaurus munozi. Stenorhynchosaurus displays a series of features which differentiate it from all the other Cretaceous pliosaurid genera: the anterior of the vomer, in ventral view, posterior of the palatal premaxilla-maxilla suture, contacting the posterior palatal process of the premaxilla level with the third maxillary alveolus; rostrum narrow and elongated with straight sides in dorsal view; lacrimal forming the anterior border and greater part of the ventral border of the orbit and broadly borders the maxilla anteriorly; anterior interpterygoid vacuity present; internal nares located between vomer and maxilla at the level of 13 th-15 th maxillary alveoli; anterior of rostrum and mandible without lateral expansion or marked increase in size of the functional alveoli; penultimate premaxillary alveolus slightly larger than adjacent premaxillary alveoli; homodont maxillary functional alveoli, with fourth tooth positions very slightly enlarged with respect to the neighboring alveoli; homodont dentary dentition; and epipodials extremely short. Based on morphological analysis of phylogenetic characters, Stenorhynchosaurus most likely nests within the increasingly inclusive Pliosauridae and Pliosauroidea, however, as currently defined, firm inference for referral of Stenorhynchosaurus to Thalassophonea is much more problematic, but ultimately seems likely based on characters shared with Pliosaurus and Brachaucheninae. However, this uncertainty indicates Thalassophonea requires rigorous redefinition. As to whether Stenorhynchosaurus is a member of the currently exclusively Jurassic genus Pliosaurus, or the Cretaceous sub-family Brachaucheninae, remains equivocal.

Metriorhynchid thalattosuchians represent the most extreme archosaurian adaptation to the marine realm.
Metriorhynchids possess aquatic adaptations throughout the skeleton. These adaptations were so extensive that some have
suggested that they lost the ability to move on land, yet their evolutionary timing remains unresolved. The closest relatives of
the metriorhynchoids, the teleosauroids, lack these aquatic adaptations, and the earliest metriorhynchoids are known
exclusively from cranial material. Here I describe a partial skull with associated forelimb elements of a new marine
crocodylomorph, Zoneait nargorum, gen. et sp. nov., of Aalenian–Bajocian age from the Snowshoe Formation of east-central
Oregon. Phylogenetic analysis identifies Zoneait as the sister taxon to Metriorhynchidae. It possesses a derived skull with
orbits that are more laterally directed and prefrontals that are more expanded than in other basal metriorhynchoids. The
preserved forelimb elements are less derived. The humerus is elongate in comparison with that of other metriorhynchoids.
The ulna is slightly reduced in length and flattened but resembles the teleosauroid condition more so than the plate-like
element of metriorhynchids. This suggests that marine adaptations in metriorhynchoids were acquired in mosaic fashion, with
modifications of the skull preceding forelimb reduction, with this forelimb reduction occurring first in the zeugopodial
elements, prior to reduction of the humerus. This evolutionary timing has important implications for the transition from
nearshore ambush predation to pelagic open-marine predation in Thalattosuchia, suggesting that adaptations related to prey
detection and capture preceded the locomotor adaptations that allowed these organisms to fully invade the oceans.

The rostrum fragment of an ichthyosaur from Northland in New Zealand is described. The specimen appears to belong to the genus Platypterygius. It is the first Mesozoic marine vertebrate fossil reported from Northland and the first cranial element of a Cretaceous ichthyosaur from New Zealand. The fragment is, unfortunately, of uncertain provenance and could have come from the widespread Northland Allochthon (Early Cretaceous–Oligocene) or the allochthonous Houhora Complex (late Early Cretaceous) or Whatuwhiwhi Formation (latest Early to Late Cretaceous), perhaps by way of initial erivation from the Early Miocene Omapere Conglomerate.

The Early Jurassic ichthyosaur Ichthyosaurus displays a variety of bony features surrounding the external naris: a small triangular process on the lacrimal protruding into the external naris; a raised edge on the posterior portion of the naris formed by the lacrimal; or an arc-shaped bone at the posterior end of the naris. These features demarcate a circular, posterior region of the external naris. Similar features also occur in the narial region of other Early Jurassic taxa, including Temnodontosaurus, Leptonectes, Excalibosaurus, and Hauffiopteryx. Additionally, Leptonectes tenuirostris displays a protrusion or flange on the nasal that extends over the external naris. In the more derived ophthalmosaurid ichthyosaurs, bony structures around the naris are more pronounced. Large processes on the nasal almost separate the naris into two openings in Sveltonectes and Muiscasaurus. In other taxa (e.g., Simbirskiasaurus birjukovi, Arthropterygius thalassonotus) the naris is completely subdivided into two openings. A subdivided naris occurred in ophthalmosaurine ophthalmosaurids as early as the Oxfordian (Late Jurassic) in Baptanodon natans, as described here. Recent work interprets the complete partitioning of the naris as separate openings to accommodate the functions of air exchange and salt excretion. The bony structures seen in Early Jurassic taxa are probably precursors to the complete bony subdivision of the naris and might be related to the presence of nasal salt glands.

Pliosaurier gehören zu den größten Meeresreptilien, die je gelebt haben. Vom Mittleren Jura bis in die obere Unterkreide erreichten einige Gattungen gigantische Ausmaße und standen meist an der Spitze der Nahrungskette. In den letzten Jahren haben besonders zwei Pliosaurier-Funde das Interesse der Öffentlichkeit erregt. Einer davon ist als „Monster von Aramberri“ bekannt geworden. Es handelt sich dabei um ein unvollständiges Skelett aus dem Kimmeridgium von Mexiko, dessen fossile Überreste von Buchy et al. (2003) als nicht näher bestimmbarer Pliosauride beschrieben wurden. Das Tier erreichte vermutlich eine Gesamtlänge von 15 m. Der zweite populär gewordene Fund, gleichfalls ein unvollständiges Skelett, stammt aus dem Tithonium von Svalbard (Spitzbergen) und erhielt den Spitznamen „Predator X“. Das Exemplar wurde von Knutsen et al. (2012) als neue Art der Gattung Pliosaurus, Pliosaurus funkei beschrieben und erreichte vermutlich eine Länge von zwischen 10 und 13 m. Keiner der uns bekannten Funde von Pliosauriern mit Längen von mehr als 10 m ist vollständig. Meist werden lediglich fragmentarische Reste von Skeletten entdeckt, die oft auch eher schlecht erhalten sind.
Keywords: Pliosauridae, Liopleurodon, Pliosaurus giganteus, Thaumatosaurus, Jurassic, Germany

The most aggressive reptile is Crocodylus porosus (CPO), the saltwater crocodile. CPO can tolerate saline environments and typically found in brackish water around coastal areas. The study from Charles Darwin University stated the agonistic behaviour is actually hard-wired since the age of juveniles until adult and CPO shows the most agony compared to the other crocodilian. However, past studies are only conducted to determine the aggression of juveniles. Therefore, observation on the behaviour of captive CPO specifically for adults is needed and in Malaysia, the ethology of CPO is still lacking. This study determined: the characteristics of captive CPO and their housing environment in Tuaran Crocodile Farm; the value of stock density related to aggression of CPO through observation at daylight, night, during feeding, and non-feeding time; and, the courtship and egg-laying behaviour, with the preferred nesting site of CPO during their mating season. The agonistic behaviour of CPO was determined in past studies, as dawn and dusk is when the species shows most aggression with tail-wagging and side-head strike (TWSHS) as its common behaviour. By interviews towards farm crews in Tuaran Crocodile Farm, structure details of the housing environment were determined, and, the parameters of the water from the housing and the surrounding temperature were also obtained. A thorough observation, comprising daylight and night with feeding and non-feeding time, were also conducted. The courtship and egg-laying behaviours were observed with the preferences of CPO’s nesting site that were also profoundly explained. The behaviour observations were recorded in the data quantification according to the behaviour stated from past studies. The data obtained from the observations were then analysed using Morpurgo et al. method (1993) with rectification on data reliability using IBM SPSS Statistics 22. Findings of the study regarding the housing environment stated that it meets the requirement for sustainable captivity system of CPO with 20 ppt salinity and proper housing structure. The results reveal that captive CPO in Tuaran Crocodile Farm is most aggressive at daylight and specifically during feeding time with stock density related to aggression value equals to 8.06 events/min observed in a density 0.3 crocodiles/m2. Its most exhibited behaviour which is TWSHS and the additional of courtship and egg-laying behaviours were scientifically stated in the study. The findings here can be used for further explanation while studying the ethology of CPO specifically on students who are interested in marine reptiles as to conduct the real study in the wild is very difficult, time-consuming, and extremely dangerous.

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but...

Woolungasaurus glendowerensis erected by PERSSON, 1960, was based on an incomplete postcranial skeleton, comprising cervical, pectoral, dorsal and caudal vertebrae, an almost complete sacrum, as well as elements of the pectoral and pelvic girdles and of the fore and hind paddles. Following comparisons with specimens referable to all valid genera of the Elasmosauridae, this specimen and additional material is identified as belonging to the genus Styxosaurus. It is the earliest record of this genus and the first in the Southern Hemisphere.

Step back to a time when Australia's red centre was flooded by a vast shallow ocean, the Eromanga Sea.  While dinosaurs stalked the scattered islands that made up the Australian continent, giant marine reptiles rule teh waves.  Plesiosaurs and ichthyosaurs swam in an inland sea filled with schools of ammonites, pterosaurs flew overhead and giant carnivorous amphibians lurked in the rivers. 'Prehistoric Marine', the third in the Museum Victoria Nature series, is a guide to the fauna of the Eromanga Sea and its coasts during the Cretaceous period. This richly illustrated book brings to life yet another aspect of the fascinating world of Australia's prehistoric past.
Copies available from https://museumvictoria.com.au/about/mv-blog/sep-2015/prehistoric-marine-life-in-australias-inland-sea/

During the Late Jurassic, important palaeogeographic events occurred in Eurasia, North America and Gondwana. Continental rift, subduction and orogeny produced different levels of marine inundation of terrestrial systems, with rising sea level. Shallow epicontinental seaways started to separate North America from Eurasia, Gondwana, and also between segments of Gondwana itself. Tethys, the east-west seaway, expanded and at times covered large parts of the continental interior of Eurasia. The aperture of new seaways such as the Greenland-Norwegian seaway and the Mezen-Pechora strait system in the northern hemisphere; the Hispanic Corridor, between North and South America; and the Trans-Erythrean seaway (or South Africa/Rocas Verdes seaway) in the southern hemisphere allowed for intermittent interchange of invertebrate and marine vertebrate faunas.
During the past five years, the ichthyosaur fossil record has provided a way to describe new species so as to complement diagnoses of species that for a long time had been either synonymised or considered invalid. These taxonomic studies allow us now to understand the paleo-distribution of the ichthyosaurs around the world better as the relationships between the realms of the northern-southern hemisphere and boreal regions. The present report is a generic-level analysis of the dispersal routes of ichthyosaurs during the Late Jurassic compared with one of its top predators, Pliosaurus, and the palaeogeographic significance of high-latitude species such as Arthropterygius spp., Undorosaurs spp., Cryopterygius spp, Janusaurus and non-ubiquitous ichthyosaurs.

Se resumen los registros de ictiosaurios (Reptilia: Ichthyosauria) conocidos hasta la fecha en Chile. Los
hallazgos en el norte del país incluyen abundantes registros desde el Triásico tardío hasta el Jurásico
Medio, sin embargo, el material es hasta ahora fragmentario y poco diagnóstico, correspondiendo
en todos los casos a Ichthyosauria indet. Por otro lado, los hallazgos en el extremo sur del país han
proporcionado abundantes restos articulados, los que al presente permiten documentar la presencia del
género Platypterygius y de la familia Ophthalmosauridae. El conjunto de hallazgos en Chile cuenta
con el registro más antiguo del grupo en Sudamérica e incluye uno de los yacimientos con preservación
excepcional de ictiosaurios del Cretácico Inferior, representando un importante potencial para la
comprensión del grupo y su distribución durante dicho lapso.

Thalassomedon haningtoni is one of the most thoroughly documented elasmosaurids. The type specimen, a nearly complete skeleton representing an osteologically mature individual with a well preserved postcranium (but damaged skull) was found in Cenomanian strata of the Graneros Shale in Colorado, USA. The only comprehensive description of this specimen produced so far is that of Welles (1943); however, his interpretations are contentious and require substantial updating relative to subsequent elasmosaurid discoveries. A second
specimen of T. haningtoni is also known from the Cenomanian Graneros Shale of Nebraska, USA. This skeleton comprises a well preserved skull and articulated series of cervical, pectoral and a few dorsal vertebrae. Welles (1970) briefly mentioned the Nebraska T. haningtoni material in a newspaper article, and both Carpenter (1999) and Sato (2002) provided an interpretation of its skull. The osteologically immature elasmosaurid remains of Alzadasaurus riggsi, found likewise in Cenomanian strata of the Belle Fourche Formation in Montana, USA, was referred to T. haningtoni by Carpenter (1999); however, most of these remains are fragmentary and heavily distorted and they are insufficient for a confident diagnosis. It therefore cannot be referred to Thalassomedon with certainty and is best considered a nomen
dubium. Since Welles’ (1943) original documentation of T. haningtoni is flawed, and a detailed account of the Nebraska specimen has not yet emerged, we reassessed the material first-hand in order to interpret its character states and phylogenetic implications. The postcranial elements of both, the Colorado holotype and Nebraska specimen, are virtually undistorted, and reveal classical elasmosaurid traits, including a convex ventrolateral edge of the orbit, a ventral notch and longitudinal lateral ridge on the craniad cervicals, and transversely narrow cervical ribs (see Sachs & Kear, 2015). The teeth, which bear fine apicobasal enamel striations, are pristinely preserved in the Nebraska specimen. Salient cranial features include a prominent dorsomedian ridge on the premaxilla, ventromedian crest on the mandibular symphysis, dome-shaped parietals, and circular external nares. Moreover, the co-ossified
atlas-axis complex (which is better preserved in the Nebraska specimen), bears a prominent hypophyseal ridge, and the craniad cervical centra are amphicoelous. The interclavicle is also fused with the clavicles and bears a prominent midline keel, the propodials are of near equal length but the femur is more slender than the humerus. Finally, a prominent craniolateral cornu is present on the pubis whereas a pelvic bar is absent. In conclusion, the superb preservation of the Colorado holotype and referred Nebraska specimen of T. haningtoni establish a morphological benchmark for this taxon that will be applied for determination of the contentious phylogeny of elasmosaurids and their clade boundaries. Insights into biomechanics and palaeobiology of these quintessential Cretaceous plesiosaurians are also underway.

References

Carpenter, K. (1999) Revision of North American elasmosaurs from the Cretaceous of the Western Interior. Paludicola 2: 148–173.

Sachs, S. & Kear, B. P. (2015) Fossil Focus: Elasmosaurs. Palaeontology Online 5: 1–8.

Sato, T. (2002) Description of plesiosaurs (Reptilia: Sauropterygia) from the Bearpaw Formation (Campanian–Maastrichtian) and a phylogenetic analysis of the Elasmosauridae. Unpublished D. Phil. Thesis, University of Calgary.

Welles, S. P. (1943) Elasmosaurid plesiosaurs with a description of new material from California and Colorado. University of California Publications in Geological Sciences 13: 125–215.

Welles, S. P. (1970) The longest neck in the ocean. University of Nebraska News, Vol. 50, No. 9, 2 p.

The middle to late Berriasian Bückeberg Group of northwestern Germany has yielded a number of plesiosaurian fossils. These include Europe's most complete Lower Cretaceous plesiosaurian, Brancasaurus brancai, in the fine grained, argillaceous Isterberg Formation near Gronau in Westfalen. Recently a second taxon, Gronausaurus wegneri was identified from the same locality and stratum (Hampe 2013) A higher diversity in the Bückeberg Group plesiosaurian assemblage is indicated by pliosauromorph and other plesiosaurian vertebrae from strata in the upper part of the sequence (see e.g. Koken 1896; Hornung et al., 2013), and both vertebrae and rib components described as Plesiosaurus degenhardti, from sandstones of the more marginal Deister Formation near Obernkirchen, Lower Saxony (Koken 1896).
The only plesiosaurian cranial remains thus far documented from the Bückeberg Group were with the holotype specimens of B. brancai, and G. wegneri. These collectively characterize the classical "plesiosauromorph" morphology of a comparatively small head, long neck and slender conical teeth. Here we report on a newly discovered incomplete mandible representing a large-skulled, macrophagous plesiosaurian found within the coarse-grained nearshore facies from the Deister Formation of the Bückeberge range, probably near Obernkirchen. The more complete mandibular ramus of this specimen measures 315 mm. It also displays a terminal rosette-like procumbent tooth array in the symphyseal region, which is curiously reminiscent of Lower Jurassic rhomaleosaurids and the Middle Jurassic pliosaurid Simolestes vorax. The tooth rosette has a maximum diameter of 90 mm and comprises five large circular to ovoid alveoli and a smaller caudalmost alveolus. The most complete second alveolus on the left side measures 15 mm in labiolingual diameter. A prominent lateral concavity at the caudal end of the rosette probably accommodated a large caniniform tooth from the upper jaw. Comparison of the Deister Formation "pliosauromorph" mandible with those of Simolestes vorax suggests a maximum cranial length of about 600 mm. As is typical for the Deister Formation sandstones, the "pliosauromorph" jaw is preserved as a highly detailed, undeformed impression remaining after removal of the soft, clay-like replacement of the skeletal material. This preservation mode commonly preserves structures in 3D, including in this case details of the vascular canals, dental lamina foramina and caudomedial symphyseal articulation. As a method to obtain a positive representation of these specimens, classically artificial casts in gypsum or latex were prepared. We employed
photogrammetry to create a high-resolution 3D model, which then was inverted in order to generate a digital cast of the specimen. Although incomplete, the Deister Formation "pliosauromorph" provides new insights into the surprising diversity of the Bückeberg Group plesiosaurian assemblage, which occupied limnic to brackish epicontinental settings incorporating only temporary connections to the sea. The sauropterygians competed in their role as aquatic predators with an abundant crocodilian fauna.

References
Hampe, O. (2013) The forgotten remains of a leptocleidid plesiosaur (Sauropterygia: Plesiosauroidea) from the Early Cretaceous of Gronau (Münsterland, Westphalia, Germany). Paläontologische Zeitschrift 87: 473–491.

Hornung, J.J., Sachs, S. & Kear, B.P. (2013) Sauropterygian fossils from the predominantly limnic–brackish Bückeberg Formation (Berriasian–Early Valanginian, Early Cretaceous) of northwestern Germany – diversity, distribution, and palaeoecology. In: Reitner, J.,
Yang, Q., Wang, Y. & Reich, M. (eds) Palaeobiology and Geobiology of Fossil Lagerstätten through Earth History. Göttingen: Universitätsdrucke, 75.

Koken, E. (1896) Die Reptilien des norddeutschen Wealden – Nachtrag. Geologische und Palaeontologische Abhandlungen 7: 119–126.

From one of the most complete Lower Cretaceous rock sequences in the world (in Villa de Leiva region, central Colombia), we describe a new genus and species of pliosaurid plesiosaur Stenorhynchosaurus munozi. Stenorhynchosaurus displays a series of features which differentiate it from all the other Cretaceous pliosaurid genera: the anterior of the vomer, in ventral view, posterior of the palatal premaxilla-maxilla suture, contacting the posterior palatal process of the premaxilla level with the third maxillary alveolus; rostrum narrow and elongated with straight sides in dorsal view; lacrimal forming the anterior border and greater part of the ventral border of the orbit and broadly borders the maxilla anteriorly; anterior interpterygoid vacuity present; internal nares located between vomer and maxilla at the level of 13 th-15 th maxillary alveoli; anterior of rostrum and mandible without lateral expansion or marked increase in size of the functional alveoli; penultimate premaxillary alveolus slightly larger than adjacent premaxillary alveoli; homodont maxillary functional alveoli, with fourth tooth positions very slightly enlarged with respect to the neighboring alveoli; homodont dentary dentition; and epipodials extremely short. Based on morphological analysis of phylogenetic characters, Stenorhynchosaurus most likely nests within the increasingly inclusive Pliosauridae and Pliosauroidea, however, as currently defined, firm inference for referral of Stenorhynchosaurus to Thalassophonea is much more problematic, but ultimately seems likely based on characters shared with Pliosaurus and Brachaucheninae. However, this uncertainty indicates Thalassophonea requires rigorous redefinition. As to whether Stenorhynchosaurus is a member of the currently exclusively Jurassic genus Pliosaurus, or the Cretaceous sub-family Brachaucheninae, remains equivocal. Stenorhynchosaurus munozi, gen. et sp. nov. un pliosaurido nuevo del barremiano superior (Cretácico Inferior) de Villa de Leiva, Colombia, Suramérica Resumen Se describe un nuevo género y especie de pliosáurido, Stenorhynchosaurus munozi, procedente de una de las secuencias de rocas del Cretácico Inferior más completas del mundo (en la región de Villa de Leiva, centro de Colombia). Stenorhynchosaurus exhibe una serie de características que lo diferencian de los demás géneros de pliosáuridos cretácicos: extremo anterior del vómer en vista ventral en posición posterior a la sutura palatal premaxilar-maxilar, contactando al proceso palatal del premaxilar al nivel del tercer alveolo maxilar; rostro angosto y alargado con lados rectos en vista dorsal; lagrimal formando el borde anterior y gran parte del borde ventral de la órbita y limitando ampliamente el maxilar anteriormente; cavidad inter-pterigoidea presente; narinas internas ubicadas entre el vómer y el maxilar, al nivel de los alvéolos 13 y 15; parte anterior del rostro y de la mandíbula sin expansión lateral o incremento marcado en el tamaño de los alvéolos funcionales; penúltimo alvéolo premaxilar ligeramente más grande que los adyacentes; alvéolos funcionales maxilares homodontes, el cuarto apenas más grande que los adyacentes; dentición dentaria homodonte; y epipodios extremadamente cortos. Con base en un análisis de caracteres filogenéticos, Stenorhynchosaurus corresponde con mayor seguridad a los cada vez más incluyentes Pliosauridae and Pliosauroidea, mientras la inferencia para referir Stenorhynchosaurus a Thalassophonea es más problemática, pero finalmente parece probable basada en caracteres compartidos con Pliosaurus y Brachaucheninae. Esta incertidumbre indica que Thalassophonea require de una redefinición rigurosa. Decir si Stenorhynchosaurus es un miembro del género Pliosaurus, por ahora exclusivamente jurásico, o de la subfamilia Brachaucheninae, es equívoco. A new Barremian pliosaurid from Colombia 85 Rev. Acad. Colomb. Cienc. Ex. Fis. Nat. 40(154):84-103, enero-marzo de 2016

This paper examines the preservational peculjarities of an elasmosau d plesiosaur skull from the Low€r Crctaceous ofcentral Queensland, Australia. This skull, previously referred to the genus lloolungasaurus, transpires to b€ so grossly distorted that even its basic anatomy will require complete reappraisal. Here we present a brief clarification of the skull's original form and true orientation. Aside from being crushed and distorted, the Woolungasawus skull bears a series of large tooth-marks, evidenlly inflict€d by a predator. In their siz€ and spacing thes€ tooth-marks find their closest match in the dentition of the gianl sympat c pliosaur 1(:ronordurrs. These tooth-marks are the first direet evidence of pliosaur predation on an elasmosaur ; th€y carry interesting implications for current unde$tanding of pliosaur feeding behaviour.

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic–Cretaceous boundary (JCB), and one (resulting in total extinction) at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in ...

Metriorhynchids were a peculiar group of fully marine Mesozoic crocodylomorphs, some of which reached large body size and were probably apex predators. The estimation of their total body length in the past has proven problematic. Rigorous size estimation was provided using five complete metriorhynchid specimens, by means of regression equations derived from basicranial and femoral length against total body length. The use of the Alligator femoral regression equation as a proxy to estimate metriorhynchid total body length led to a slight underestimation, whereas cranial regression equations of extant genera resulted in an overestimation of body length. Therefore, the scaling of crania and femora to total body length of metriorhynchids is noticeably different from that of extant crocodylians, indicating that extant crocodylians are not ideal proxies for size reconstruction of extinct taxa that deviate from their semi-aquatic morphotype. The lack of a correlation between maximum, minimum, or the range of generic body lengths with species richness demonstrates that species diversification is driven by factors other than just variation in body size. Maximum likelihood modelling also found no evidence for directionality in body size evolution. However, niche partitioning in Metriorhynchidae is mediated not only by craniodental differentiation, as shown by previous studies, but also by body size variation.

Recent revision of the marine metriorhynchid crocodilians indicates that a partial skull previously assigned to the species Metriorhynchus superciliosus and newly discovered postcranial elements from the Kimmeridge Clay of Westbury, Wiltshire belong to a new species of metriorhynchid. This material is herein described and referred to a new species of the genus Dakosaurus, characterised by four apomorphies: the size and shape of the enlarged supratemporal fossae; relatively large teeth, and half the number in relatives; the robust and unornamented cranium; and the angle that the prefrontal makes with the long axis of the skull. In a new phylogenetic analysis, Dakosaurus carpenteri sp. nov. is the basal member of a clade containing also D. maximus and D. andiniensis: it is not so short-snouted and its teeth are not so few and large as in the other two species, but the new form illustrates the ecological transition among metriorhynchids from a piscivorous diet to high-order carnivory.

Mosasaurids (Mosasauridae) were specialized marine lizards that evolved and radiated in the Late Cretaceous. Their diversity peaked in the Maastrichtian, with the most diverse faunas known from Morocco. Here we describe a new species of mosasaurid from this fauna. Pluridens serpentis sp. nov.  is described based on two complete skulls and referred jaws. It is referred to Pluridens based on the elongate and robust jaws, small teeth, and specialized tooth implantation. Pluridens is referred to Halisaurinae based on the posteriorly expanded premaxilla, long premaxilla-maxilla suture, broad premaxillary facet on the maxilla, closed otic notch, and small, striated, hooked teeth. The orbits are reduced relative to other halisaurines while the snout is robust and flat with a broad, rounded tip. The jaws bear numerous small, hooked, snake-like teeth. Skulls imply lengths of 5-6 meters; referred material suggests lengths of ≥10 meters. Pluridens’ specialized morphology – especially the contrasting large size and small teeth - suggests a distinct feeding strategy. Small orbits imply that P. serpentis relied on nonvisual cues including touch and chemoreception during foraging, as in modern marine snakes. Numerous neurovascular foramina on the premaxillae are consistent with this idea. The small teeth suggest proportionately small prey. The dentary becomes massive and robust in the largest individuals, suggesting sexual selection and perhaps sexual dimorphism, with the mandibles possibly functioning for combat as in modern beaked whales and lizards. The new mosasaur emphasizes how Maastrichtian mosasaurids were characterized by high species richness, functional diversity of niches occupied, and a certain degree of endemism, i.e. geographic specialization. and  continued diversifying until the end of the Cretaceous, just prior to the K-Pg extinction.

Recent descriptions of new taxa and recognition of survivorship of Jurassic genera across the Jurassic-Cretaceous boundary bring the total number of Cretaceous ichthyosaur genera to eight. Taxa currently known from the Cretaceous include Ophthalmosaurus, Caypullisaurus, Aegirosaurus, Platypterygius, Maiaspondylus, Athabascasaurus, Sveltonectes, and Acamptonectes. This review summarizes the occurrence of all Cretaceous genera. A discussion of morphological diversity demonstrates the different, though overlapping, ecological niches occupied by the different taxa, while the comparison of phylogenetic hypotheses shows the problems inherent in understanding the evolutionary relationships between Cretaceous genera. The Late Jurassic radiation indicated in the competing phylogenetic hypotheses may correlate with the opening of the Atlantic Ocean or additional dispersal routes established by the breakup of Gondwana. Inclusion of the stratigraphically oldest Platypterygius species may aid in resolving these evolutionary relationships.

Cretaceous marine amniote fossils have been documented from Australia for more than 150 years, however, their global significance has only come to the fore in the last decade. This recognition is a product of accelerated research coupled with spectacular new discoveries from the Aptian–Albian epeiric sequences of the Eromanga Basin – especially the opal-bearing deposits of South Australia and vast lagerstätten exposures of central-northern Queensland. Novel fragmentary records have also surfaced in Cenomanian and Maastrichtian strata from Western Australia. The most notable advances include a proliferation of plesiosaurian taxa, as well as detailed characterization of the 'last surviving' ichthyosaurian Platypterygius, and some of the stratigraphically oldest protostegid sea turtles based on exceptionally preserved remains. Compositionally, the Australian assemblages provide a unique window into the otherwise poorly known Early Cretaceous marine amniote faunas of Gondwana. Their association with freezing high latitude palaeoenvironments is also extremely unusual, and evinces a climate change coincident diversity turnover incorporating the nascent radiation of lineages that went on to dominate later Mesozoic seas.

Polycotylids were a predominately Late Cretaceous radiation of large-skulled “pliosauromorphs” whose remains are found globally after a sudden appearance in the rock record at around the Aptian-Albian boundary. The stratigraphically oldest fragmentary polycotylid fossils occur in Aptian polar epeiric sediments of what is now southern Australia (Kear 2005). Cladistic topologies have additionally referred several coeval “pliosauromorph” taxa scored from associated or articulated skeletons: the early Aptian “Leptocleidus” clemai; and early Aptian–earliest Albian Umoonasaurus democyllus. Unfortunately, the osteology of these archetypal species has not been sufficiently documented, and indisputable polycotylids from sympatric strata have yet to be formally described. Moreover, the Gondwanan emergence of Polycotylidae has been contested by the recognition of early Albian remains from Boreal high-latitude deposits in North America (Druckenmiller & Russell 2009). To explore these palaeobiogeographical scenarios and provide a comprehensive appraisal of the Australian fossils, a sequence of S-DIVA, Bayesian Binary MCMC, and Lagrange optimization analyses were implemented across parsimony and Bayesian tree topologies derived from taxon-rich datasets of Plesiosauria. The results confirmed a Gondwanan polar dispersal deep within the polycotylid lineage, although seminal migrations amongst leptocleidians seem to have occurred from the northern hemisphere across the palaeo-Atlantic and Tethyan margin. Updated anatomical information for Australian polycotylids has further identified a new Gondwanan high-latitude taxon from the upper Albian Allaru Mudstone of Queensland. The unequivocal phylogenetic positioning of this specimen renders it amongst the most basal austral exemplars of the clade.

References

Druckenmiller, P.S. & Russell, A.P., (2009). Earliest North American occurrence of Polycotylidae (Sauropterygia: Plesiosauria) from the Lower Cretaceous (Albian) Clearwater Formation, Alberta, Canada. Journal of Paleontology 83: 981-989.

Kear, B.P., (2005) Marine reptiles from the Lower Cretaceous (Aptian) deposits of White Cliffs, southeastern Australia: implications of a high-latitude cold water assemblage. Cretaceous Research 26: 769-782.

Metriorhynchoid crocodylians represent the pinnacle of marine specialization within Archosauria. Not only were they a major component of the Middle Jurassic-Early Cretaceous marine ecosystems, but they provide further examples that extinct crocodilians did not all resemble their modern extant relatives. Here, we use a varied toolkit of techniques, including phylogenetic reconstruction, geometric morphometrics, diversity counts, discrete character disparity analysis, and biomechanical finite-element analysis (FEA), to examine the macroevolutionary history of this clade. All analyses demonstrate that this clade became more divergent, in terms of biodiversity, form, and function, up until the Jurassic-Cretaceous boundary, after which there is no evidence for recovery or further radiations. A clear evolutionary trend towards hypercarnivory in Dakosaurus is supported by phylogenetic character optimization, morphometrics, and FEA, which also support specialized piscivory within Rhacheosaurus and Cricosaurus. Within Metriorhynchoidea, there is a consistent trend towards increasing marine specialization, with the hypermarine Cricosaurus exhibiting numerous convergences with other Mesozoic marine reptiles (e.g. loss of the deltopectoral crest and retracted external nares). In addition, biomechanics, morphometrics, and characterdisparity analyses consistently distinguish the two newly erected metriorhynchid subfamilies. This study illustrates that together with phylogeny, quantitative assessment of diversity, form, and function help elucidate the macroevolutionary pattern of fossil clades.

The Lower Cretaceous (Aptian-Albian) southern high latitude deposits of Australia have yielded a diverse range of marine
reptile fossils. Ichthyosaurs and at least five distinct plesiosaur taxa have been recorded. Most of the current marine reptile specimens are derived from the predominantly Aptian Bulldog Shale and Wallumbilla Formation. These units, famous for producing opal, represent shallow epicontinental marine depositional environments. Fragmentary plesiosaur remains have also been recovered from high latitude non-marine deposits of the Wonthaggi, Eumeralla, and Griman Creek formations. These are Aptian to middle Albian in age, and comprise fine-grained fluviatile/estuarine sediments laid down in inland rift valleys and coastal flood plains near the Cretaceous southern polar circle. Estimates of palaeolatitude place most of southern Australia at around 60o to 80o S during the late Early Cretaceous. Sedimentary structures, fossils, isotope data, and climatic modeling indicate highly seasonal cool-cold conditions possibly with winter freezing. This contrasts markedly with climate regimes typically tolerated by modern aquatic reptiles, but suggests that some Mesozoic forms may have possessed adaptations to cope with low average water temperatures.

Marginal tooth crowns from the hypercarnivorous marine reptile Mosasaurus hoffmannii Mantell, 1829 are reported for the first time from the Late Cretaceous (Maastrichtian) phosphates of Morocco. Fossilized remains of this species are previously known from Campanian and Maastrichtian outcrops in Europe, North America, and western Asia at a paleolatitudinal belt of 30-45°N. New fossil material originates from the Upper Couche III layer of the Oulad Abdoun Basin, south of Oued Zem, Morocco. The discovery of M. hoffmannii in Morocco extends its paleobiogeographic range south to 25°N and into the southern margin of the Mediterranean Tethys.

In June 1977, the skeleton of a large sauropterygian marine reptile was discovered by local farmers in Vereda de Monquirá, Departamento de Boyacá, Colombia, South America. The skeleton was a large pliosaurid plesiosaur, almost complete and articulated, from the upper Aptian Arcillolitas Abrigarradas Member of the Paja Formation, which is now recognised as a Lower Cretaceous Gap (LCG) marine reptile Lagerst´'atte. The pliosaurid remains are preserved in situ, covered by the community run 'El Fósil' museum, and the skeleton has become iconic as 'The Fossil' of the Alto Ricaurte region. The scientific importance of the skeleton was recognised by its description as the holotype of a new species, Kronosaurus boyacensis. Examination of the skeleton of Kronosaurus boyacensis has revealed the need for a detailed re-description, which indicates erroneous original interpretation of various features, including: the positions of the cranial bones and openings; the location of the atlas-axis; and the interpretation of the dorsal vertebrae. Hence, we undertake a full re-description, and clarification of the morphology of the specimen. Interpretation of the taphonomic trajectory of the fossilized remains indicates collapse of the skeleton on the sea-floor, rapid burial without evidence of scavenging or epibionts, and partial preservation in early diagenetic concretions, which together permit reconstruction the original three-dimensional shape of the animal. Kronosaurus boyacensis is a remarkable specimen. It was the first of a growing number of newly described Lower Cretaceous pliosaurids from the LCG of Colombia. The holotype is an evolutionarily and palaeogeographically important Lower Cretaceous mega-predator, which highlights the importance of northern South America for the study of LCG pliosaurids. Kronosaurus boyacensis and its cohabiting marine reptiles are thereby critical to our understanding of Lower Cretaceous epicontinental seaways.

The ichthyosaur fossil record is interspersed by several hiatuses, notably during the Cretaceous. This hampers our understanding of the evolution and extinction of this group of marine reptiles during the last 50 million years of its history. Several Cretaceous ichthyosaur taxa named in the past have subsequently been dismissed and referred to the highly inclusive taxon Platypterygius, a trend that has created the impression of low Cretaceous ichthyosaur diversity. Here, we describe the cranial osteology, reassess the stratigraphic age, and evaluate the taxonomy and phylogenetic relationships of two Cretaceous ichthyosaurs from western Russia: Simbirskiasaurus birjukovi from the early Barremian and Pervushovisaurus bannovkensis from the middle Cenomanian, both formerly regarded as nomina dubia, and allocated to Platypterygius sp. and Platypterygius campylodon, respectively. We show that Simbirskiasaurus birjukovi and Pervushovisaurus bannovkensis are valid platypterygiine ophthalmosaurids, notably characterized by a peculiar narial aperture. The cranial anatomy and phylogenetic relationships of these taxa illuminate the evolution of narial aperture anatomy in Cretaceous ichthyosaurs, clarify the phylogenetic relationships among platypterygiines, and provide further arguments for a thorough revision of Platypterygius.

Background: Marine deposits from the Callovian of Europe have yielded numerous species of metriorhynchid crocodylomorphs. While common in English and French Formations, metriorhynchids are poorly known from the Iberian Peninsula. Twenty years ago an incomplete, but beautifully preserved, skull was discovered from the Middle Callovian of Spain. It is currently the oldest and best preserved metriorhynchid specimen from the Iberian Peninsula. Until now it has never been properly described and its taxonomic affinities remained obscure.

Bisher unbeschriebene Reste von marinen Tetrapoden aus dem Oberaalenium (Ludwigienton-Formation) und Oberbajocium (Parkinsonienton-Formation) von Bielefeld-Bethel werden vorgestellt. In beiden stratigraphischen Intervallen lassen sich Thalattosuchier, Ichthyosaurier und Plesiosaurier nachweisen. Dieser Befund zeigt das persistieren typischer unterjurassischer Faunenelemente tieferer Beckenbereiche in den Mitteljura hinein an, und ist von besonderem Wert, da sowohl aus dem Aalenium als auch aus dem Bajocium Mitteleuropas nur wenige Funde mariner Tetrapoden bekannt sind. Beide Faunen kamen unter transgressiven oder Hochstandsbedingungen zur Ablagerung.

Hitherto unpublished marine tetrapod remains from the Upper Aalenian (Ludwigienton-Formation) and Upper Bajocian (Parkinsonienton-Formation) of Bielefeld-Bethel are described. Both stratigraphic intervals contain remains of thalattosuchians, ichthyosaurians and plesiosaurians, which indicate the persistence of faunal assemblages similar to those from distal basinal settings of the Lower Jurassic into the Middle Jurassic. This is of special importance since marine tetrapod remains are generally rare in the Aalenian and Bajocian of Central Europe. The strata containing both assemblages were deposited under transgessive to highstand systems tract conditions.

Fossil reptiles from the Mesozoic are rarities in Nordrhein-Westfalen (western Germany), and the majority of specimens found are only fragmentarily preserved. The first report of a fossil reptile, parts of a mosasaur skeleton from the Upper Cretaceous (Cenoman) of Schöppingen, was published by W. von der Marck already in 1858. Another mosasaur from Halden (Senon) was described by Pompeckj (1910). Lommerzheim (1976) reported a nearly complete wing of an unidentified pterosaur from the Upper Cretaceous (Turon) of Dinslaken. The present repository of the poorly prepared remain is unknown. The Lower Cretaceous (Berriasian) clay-pit Gerdemann near Gronau yielded plesiosaurs, dinosaurs, and turtles. Wegner (1914) erected Brancasaurus brancai, an elasmosaurid plesiosaur represented by an almost complete skeleton and mentioned a second plesiosaur genus still to be described. Recently, two probably theropodan or crocodilian vertebrae (Sachs 1996) and a humerus of a nodosaurid (Sachs 1997) were reported. The most important finds of reptiles from Nordrhein-Westfalen have been excavated in the Lower Cretaceous (Aptium) near Nehden. Among the material are numerous remains of iguanodontids including a juvenile specimen, a possible hypsilophodont, an unidentified theropod, as weil as crocodilian and turtle remains (Norman et al. 1987). Wallücke is a rich locility in the Callovium. Michaelis et al. (1997) described plesiosaurs, an ichthyosaur, a marine crocodile, and two dinosaur genera (Lexovisaurus and Dryosaurus) from this locality, however, all designation are based on rather incomplete material. A large but incomplete ichthyosaur from the Early Jurassic (Toarcian) of Bielefeld was described by Hungerbühler & Sachs (1996) as Temnodontosaurus sp. A Middle Jurassic (Bathonian) specimen also from the Bielefeld area is too incomplete for proper identification, but could represent an ophthalmosaurid ichthyosaur (Sachs & Hungerbühler 1996).

The skull and associate cervical vertebrae of an elasmosaur from the Lower Cretaceous of northeastern Queensland are described as a new species of Tuarangisaurus, Tuarangisaurus australis. They represent the oldest record of that genus and the first secure outside New Zealand. A phylogenetic analysis based on 19 characters of the skull and cervical vertebrae is undertaken. One tree is presented, including all valid members of the Elasmosauridae for which sufficient cranial material is known. The results give an example for the interrelationship of the Elasmosauridae and show the probable position of Tuarangisaurus.

Fossils of Mesozoic vertebrates are rare in Scotland, particularly specimens of marine reptiles such as plesiosaurs and ichthyosaurs. We describe a suite of ichthyosaur fossils from the Early to Middle Jurassic of Skye, which to our knowledge are the first ichthyosaurs from Scotland to be described and figured in detail. These fossils span approximately 30 million years, from the Sinemurian to the Bathonian, and indicate that ichthyosaurs were a major component of Scottish marine faunas during this time. The specimens include isolated teeth that could represent the most northerly known occurrences of the widespread Sinemurian species Ichthyosaurus communis, a characteristic component of the famous Lyme Regis faunas of England, suggesting that such faunas were also present in Scotland during the Early Jurassic. An associated humerus and vertebrae from Toarcian-Bajocian-aged deposits are named as a new genus and species of basal neoichthyosaurian, Dearcmhara shawcrossi. The taxonomic affinities of this taxon, which comes from a critical but poorly sampled interval in the fossil record, suggest that non-ophthalmosaurid neoichthyosaurians dominated European assemblages around the Early-Middle Jurassic boundary, and were later replaced by ophthalmosaurids, whose radiation likely took place outside Europe. Many of these specimens were collected by amateurs and donated to museum collections, a cooperative relationship essential to the preservation of Scotland's fossil heritage.