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FHSM VP-5515 is a medium-sized russellosaurine mosasaur collected in the 1970s in Logan County, western Kansas, USA. A suite of cranial features are unique to this specimen at the species level. One is a conspicuous lack of a predental rostrum on the premaxilla, whose dentigerous portion is spatula shaped in dorsoventral aspect. Furthermore, the frontal of FHSM VP-5515 exhibits the following unique combination of features: (1) the median dorsal keel absent; (2) straight, long preorbital borders converging anteriorly at 30[degrees] from each other; and (3) supraorbital border thick and extensive, clearly separating the prefrontal and the postorbitofrontal above the orbit. The fifth character pertains to the uniquely square outline of the intramandibular joint surface of the splenial, resulting from a robust dorsomedial flange. Finally, hitherto unreported on any mosasaur jaws, a deep notch excavates the dorsal border of the articular immediately posterior to the glenoid fossa. Examination of preexisting Ectenosaurus specimens suggests that this articular notching diagnoses the genus. Based on the unique suite of characteristics including the articular notch, we consequently hypothesize the following for FHSM VP-5515: (1) it is most comparable with the enigmatic russellosaurine Ectenosaurus clidastoides (Merriam, 1894); and (2) it represents a new species of Ectenosaurus. Key words: Mosasauridae, Plioplatecarpinae, Ectenosaurus, new species, Late Cretaceous, Smoky Hill Chalk Member. FHSM VP-5515 est un mosasaure russellosaurine de taille moyenne preleve dans les annees 1970 dans le comte de Logan (ouest du Kansas, Etats-Unis). Un ensemble d'elements craniens n'est observe quechez cespecimen a l'echelle de l'espece. Parmi ces elements figure l'absence evidente d'un rostre predentaire sur le premaxillaire, dont la portion dentigere est en forme de spatule en vue dorsoventrale. L'os frontal de FHSM VP-5515 presente en outre la combinaison unique suivante d'elements: (1) l'absence d'une quille dorsale mediane, (2) des bordures preorbitales longues et droites conver-geant anterieurement a 30[degrees] l'unedel'autre et (3) une epaisse et vaste bordure supraorbitale separant clairement le prefrontal et le postorbitofrontal au-dessus de l'orbite. Le cinquieme caractere concerne la silhouette singulierement carree de la surface de l'articulation intramandibulaire du splenial, qui produit une collerette dorsomediale robuste. Enfin, une encoche profonde, jusqu'ici jamais documentee sur une machoire de mosasaure, creuse la bordure dorsale de l'articulaire immediatement derriere les fosses glenoides. L'examen de specimens preexistants d'Ectenosaurus donne a penser que cette encoche sur l'articulaire est diagnostique du genre. A la lumiere de l'ensemble singulier de caracteristiques incluant l'encoche de l'articulaire, nous postulons donc ce qui suit en ce qui concerne FHSM VP-5515: (1) il s'apparente le plus au russellosaurine enigmatique Ectenosaurus clidastoides (Merriam, 1894) et (2) il represente une nouvelle espece d'Ectenosaurus. Mots-cles: mosasaurides, plioplatecarpines, Ectenosaurus, nouvelle espece, Cretace tardif, membre crayeux de Smoky Hill., Introduction In 1967, Russell established a new plioplatecarpine genus, Ectenosaurus, to which he reassigned Platecarpus clidastoides Merriam, 1894. After more than 50 years since its establishment, the genus Ectenosaurus continues [...]

Modern squamates (lizards, snakes and amphisbaenians) are the world's most diverse group of tetrapods along with birds.sup.1 and have a long evolutionary history, with the oldest known fossils dating from the Middle Jurassic period--168 million years ago.sup.2-4. The evolutionary origin of squamates is contentious because of several issues: (1) a fossil gap of approximately 70 million years exists between the oldest known fossils and their estimated origin.sup.5-7; (2) limited sampling of squamates in reptile phylogenies; and (3) conflicts between morphological and molecular hypotheses regarding the origin of crown squamates.sup.6,8,9. Here we shed light on these problems by using high-resolution microfocus X-ray computed tomography data from the articulated fossil reptile Megachirella wachtleri (Middle Triassic period, Italian Alps.sup.10). We also present a phylogenetic dataset, combining fossils and extant taxa, and morphological and molecular data. We analysed this dataset under different optimality criteria to assess diapsid reptile relationships and the origins of squamates. Our results re-shape the diapsid phylogeny and present evidence that M. wachtleri is the oldest known stem squamate. Megachirella is 75 million years older than the previously known oldest squamate fossils, partially filling the fossil gap in the origin of lizards, and indicates a more gradual acquisition of squamatan features in diapsid evolution than previously thought. For the first time, to our knowledge, morphological and molecular data are in agreement regarding early squamate evolution, with geckoes--and not iguanians--as the earliest crown clade squamates. Divergence time estimates using relaxed combined morphological and molecular clocks show that lepidosaurs and most other diapsids originated before the Permian/Triassic extinction event, indicating that the Triassic was a period of radiation, not origin, for several diapsid lineages.Computed tomography scanning of the Triassic fossil Megachirella wachtleri combined with a broad morphological and molecular phylogenetic analysis of reptile relationships confirm it as the most primitive stem squamate., Author(s): Tiago R. Simões [sup.1] , Michael W. Caldwell [sup.1] [sup.2] , Mateusz Talanda [sup.3] , Massimo Bernardi [sup.4] [sup.5] , Alessandro Palci [sup.6] , Oksana Vernygora [sup.1] , Federico [...]

The Paleocene deposits from the Cerrejón Formation (Colombia, South America) have provided abundant snake remains. All this material has been assigned to the giant snake Titanoboa cerrejonensis. Here, we describe six vertebrae from among the referred materials that do not correspond to Titanoboa. All six vertebrae are morphologically identical, of a similar size, and display a distinct morphology that differs from Titanoboa. This new and unnamed taxon is a large snake estimated to be around eight meters in total length. Anatomical comparisons show that these vertebrae possess certain features typical of the Palaeophiidae, a group of extinct snakes of uncertain relationships known almost exclusively from vertebrae. Among the Palaeophiidae, the new taxon resembles the more generalized forms assigned to the genus Palaeophis, but lacks the extreme aquatic adaptations that define forms assigned to the genus Pterosphenus. We regard the new taxon as an undetermined palaeophiine but do not assign it to Palaeophis as a number of features differ from that described genus. This new record expands the known diversity of aquatic snakes from the Paleogene of South America and provides a substantial new record for the paleogeographic distribution of the Palaeophiidae. The oldest records are from the Cretaceous of Africa, while Paleocene records are poorly known and restricted to Africa, North America, and Europe. The majority of vertebral forms assigned to Palaeophiidae are from the Eocene, principally from the Tethys region, with only one previous South American record coming from the Eocene of Ecuador. [ABSTRACT FROM AUTHOR]

Although the Jurassic was a period of high diversity in ichthyosaurs, only a small number of specimens have been recorded from Canada to date. We describe here a new occurrence of an ophthalmosaurid ichthyosaur from a shallow marine depositional environment within the Bowser Basin of northern British Columbia. Based on vertebral diameters and the size of the humerus, the ichthyosaur was relatively large compared to other contemporaneous forms, yet possessed teeth that were small for its body size. As well, the height to length ratio of the preserved vertebrae suggests it may have had a more elongate, less regionalized body shape. Although indeterminate at a generic level, the presence of Late Jurassic ichthyosaurs in nearshore waters of northwestern North America further demonstrates their cosmopolitan distribution. Si le Jurassique fut une periode de forte diversite chez les ichthyosaures, seul un petit nombre de specimens a ete enregistre au Canada a ce jour. Nous decrivons une nouvelle occurrence d'ichthyosaure ophthalmosauride d'un milieu de sedimentation marin peu profond dans le bassin de Bowser du nord de la Colombie-Britannique. A la lumiere du diametre des vertebres et de la taille des humerus, l'ichthyosaure etait relativement grand par rapport a d'autres formes contemporaines, mais possedait de petites dents pour la taille de son corps. Le rapport entre la hauteur et la longueur des vertebres preservees semble en outre indiquer une forme du corps plus allongee et moins regionalisee. Bien que le genre ne soit pas determine, la presence d'ichthyosaures au Jurassique tardif dans les eaux littorales du nord-ouest de l'Amerique du Nord constitue une nouvelle demonstration de leur repartition cosmopolite. [Traduit par la Redaction], Introduction Ichthyosaurs were a diverse and cosmopolitan group of highly aquatic marine reptiles that first appeared in the Early Triassic and survived until the Late Cretaceous (Sander 2000; McGowan and [...]