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Environmental changes governed the diversity of marine ecosystems and the evolution of marine reptiles during the Jurassic. Abrupt climatic changes, mainly cooling, produced crises in marine ecosystems including marine reptiles, but global warming events at the Pliensbachian/Toarcian boundary and the early Toarcian Jenkyns Event led to a second order mass extinction. The Jenkyns Event coincides with exceptional preservation of marine reptiles in black shales, so widespread extinctions are masked to some extent by increases in specimens and diversity in the Lagerstätten. Marine reptile diversity responded to this biotic crisis; in the early Toarcian, stenopterygid ichthyosaurs and marine crocodylomorphs (thalattosuchians) diversified whereas some groups that survived the Jenkyns Event disappeared during the hyperthermal conditions of the middle and late Toarcian, including ichthyosaurs (leptonectids, temnodontosaurids, baso-parvipelvians), and sauropterygians (plesiosaurids, microcleidids). After the crisis, Aalenian climates were cold and the sea-level low with a poor record of marine reptiles. The diversity of marine ecosystems increased from the early Bajocian with a turnover in ichthyosaurs (Early Jurassic ichthyosaurs were replaced by ophthalmosaurids), sauropterygians diversified and increased in size (mainly pliosaurids and cryptocleidids), and pelagosaurid thalattosuchians disappeared at the same time that machimosaurids diversified and the Metriorhynchidae appeared. Marine reptiles reached a new maximum of diversity during the Callovian, but the Callovian/Oxfordian transition was a time of climatic cooling and sea-level fall that negatively impacted on marine ecosystems, including the extinction of rhomaleosaurids. From the middle Oxfordian, the development of large epeiric platforms and increase of temperature favoured the diversification of marine ecosystems, included marine reptiles. During the Late Jurassic, ophthalmosaurids, pliosaurids, cryptocleidids, and metriorhynchids dominated, and marine turtles diversified in coastal environments (eurysternids) and open carbonate platforms (plesiochelyids and thalassemydids). [ABSTRACT FROM AUTHOR]

The geographic origins and distributional patterns of Gondwanan teleosauroids during the Jurassic have been fiercely debated over many years. Unlike the rich thalattosuchian fossil record from Laurasia, teleosauroids described from Gondwanan ecosystems are relatively scarce. Most of the known occurrences consist of isolated and fragmentary bones collected in Madagascar, Morocco, Tunisia, India, and Ethiopia. Nevertheless, these specimens, although fragmentary, have provided substantial information for assessing the evolutionary scenarios of multiple teleosauroid lineages and have shown that certain teleosauroid taxa were widespread rather than endemic to Western Europe. Here, a partial skeleton of a teleosauroid crocodylomorph is described. It was found in the late Middle Jurassic (Callovian) deposits of southeastern Tunisia by a team of French and Tunisian paleontologists; however, it has not been thoroughly studied at both macro- and microscopic scale until now. The new specimen is composed of an incomplete symphyseal portion of a lower jaw in addition to isolated teeth, osteoderms (both dorsal and ventral), thoracic and caudal vertebrae, and several thoracic ribs. The specimen has several morphological characters that are reminiscent of longirostrine teleosauroids. Due to the total absence of other cranial bones, as well as the pectoral and pelvic girdles, the specimen is not diagnostic to the generic level. However, these new remains represent the youngest ascertained occurrence of a definitive non-machimosaurin teleosauroid in Africa, provide additional insights into the geographic distribution of Thalattosuchia, and raise once again the question whether the origins of this clade were Gondwanan or Laurasian. [ABSTRACT FROM AUTHOR]

A new teleosaurid from the Lower Cretaceous of Tataouine (Tunisia), Machimosaurus rex sp. nov., definitively falsifies that these crocodylomorphs faced extinction at the end of the Jurassic. Phylogenetic analysis supports its placement closer to M. hugii and M. mosae than M. buffetauti . With the skull length up to 160 cm and an estimated body length of 10 m, M. rex results the largest known thalattosuchian, and the largest known crocodylomorph at its time. This giant thallatosuchian probably was an ambush predator in the lagoonal environments that characterized the Tethyan margin of Africa during the earliest Cretaceous. Whether the Jurassic-Cretaceous mass extinction was real or artefact is debated. The discovery of M . rex supports that the end-Jurassic crisis affected primarily Laurasian biota and its purported magnitude is most likely biased by the incomplete Gondwanan fossil record. The faunal turnovers during the J-K transition are likely interpreted as local extinction events, triggered by regional ecological factors, and survival of widely-distributed and eurytypic forms by means of habitat tracking. [ABSTRACT FROM AUTHOR]

The metriorhynchids from the Jurassic of Normandy have been known since the 19th century. However, the remains studied until now have rarely been found in anatomical connection. The acquisition of specimen MPV 2010.3.610 that was found in the Callovian of Vaches-Noires cliffs by the Paleospace Museum in 2010, allowed the first description of the most complete Metriorhynchidae from this locality so far. The analysis of this Metriorhynchidae raises questions about the taxonomic value of several criteria currently used to distinguish between the different Callovian and Oxfordian species. The study of the cranial and postcranial elements shows that this specimen presents diagnostic criteria of different Metriorhynchidae such as the shape of the prefrontals, the mandible, the palato-maxillary suture, the atlas/axis, the cervical vertebrae as well as the extension of the jugal bone and the morphology of the teeth. A discussion highlights the limitations of the current classification of Metriorhynchidae. [ABSTRACT FROM AUTHOR]

Résumé: Un manuscrit inédit daté du 30 mai 1831 montre qu’Étienne Geoffroy Saint-Hilaire faisait réaliser des dessins et des gravures de trois nouvelles espèces de crocodiles fossiles (Mesoeucrocodylia, Thalattosuchia) du jurassique de Normandie. Ces espèces sont nommées Steneosaurus aubignensis, Steneosaurus quillensis et Teleosaurus microtrèmes. Geoffroy Saint-Hilaire projetait de publier une grande étude descriptive de ces ű grands sauriens fossiles de Normandie Ƈ qu’il venait de voir lors de deux voyages successifs à Caen, fin 1830 et début 1831. Des lettres inédites conservées à la Bibliothèque de Caen et à l’American Philosophical Society ainsi que les publications de Geoffroy Saint-Hilaire permettent de retracer les différentes étapes de ce projet qu’il comptait mener à bien en étroite collaboration avec Jacques-Amand Eudes-Deslongchamps. Ce projet ne verra finalement jamais le jour. Compte tenu des spécimens de crocodiles fossiles dont Geoffroy Saint-Hilaire avait alors connaissance, il est démontré que les deux premières espèces inédites correspondent respectivement à Teleidosaurus calvadosii et Steneosaurus megistorhynchus. Par ailleurs, Teleosaurus microtrèmes correspond au nouveau nom que Geoffroy Saint-Hilaire avait l’intention de donner à Teleosaurus cadomensis dont le nom d’espèce avait été choisi par Lamouroux en 1820. Finalement, grâce aux renseignements apportés par ce nouveau document, les gravures inédites de Geoffroy Saint-Hilaire ont pu être découvertes dans les archives personnelles de Georges Cuvier conservées à la bibliothèque centrale du Muséum national d’histoire naturelle, Paris. Ces planches, longtemps considérées comme perdues, sont présentées et décrites dans cet article pour la première fois. [ABSTRACT FROM AUTHOR]

Abstract: Metriorhynchidae is a clade of marine-adapted crocodilians known from several Middle Jurassic–Early Cretaceous specimens collected predominantly in South America and Europe, but poorly known in the northern margin of Gondwana. The “Portomaggiore crocodile” is the most complete specimen of an Italian metriorhynchid to date: it consists of a partial skeleton that has been provisionally referred to an unnamed species of Late Jurassic Metriorhynchus or Geosaurus. The specimen is preserved in the reddish, nodular limestone of the Rosso Ammonitico Veronese Formation (Bajocian–Tithonian); new data on microfossil associations constrain the age of the metriorhynchid to the late Bajocian–earliest Bathonian. On the basis of cranial synapomorphies, the “Portomaggiore crocodile” falls as the closest sister-taxon of the Late Jurassic–Early Cretaceous geosaurines, and is referred to Neptunidraco ammoniticus gen. et sp. nov. It is unique among Middle Jurassic metriorhynchids in showing an incipient streamlining of the skull, shared with Late Jurassic and Cretaceous taxa. Since Neptunidraco is the oldest known member of Metriorhynchidae, its phylogenetic position supports the hypothesis that the timing of the initial metriorhynchid and geosaurine diversifications should start in the Bajocian. [ABSTRACT FROM AUTHOR]

Abstract: The fossil remains of two small reptiles recently discovered in the Sogno Formation (Lower Toarcian) near Cesana Brianza (Lecco Province), represent the first mesoeucrocodylians reported for Lombardy and some of the few Jurassic reptiles from Italy. Due to the absence of diagnostic skeletal elements (the skulls are lacking), it is not possible to refer the new specimens at genus level with confidence. Although the well developed dermal armour would characterise Toarcian thalattosuchians of the genera Steneosaurus (Teleosauridae) and Pelagosaurus (Metriorhynchidae), the peculiar morphology of the osteoderms allow to tentatively refer the remains to the latter taxon (cf. Pelagosaurus sp.). The small size, along with the opening of the neurocentral vertebral sutures and, possibly, the non sutured caudal pleurapophyses, indicate that the specimens were morphologically immature at death. These “marine crocodiles” confirm the affinities between the fauna of the Calcare di Sogno Formation and coeval outcrops of central Europe that also share the presence of similar fishes and crustaceans. [Copyright &y& Elsevier]

Enaliosuchus macrospondylus Koken, 1883 was one of the first thalattosuchian taxa from the Cretaceous to be described. The type series includes an atlas-axis complex, remnants of three post-axial cervical vertebrae, several dorsal vertebrae, a caudal vertebra, an incomplete femur and a fragmentary sacral rib from the upper Valanginian of northern Germany. Additionally, two isolated, non-thalattosuchian, tooth crowns from the uppermost Valanginian to lowermost Hauterivian of different localities in northern Germany were tentatively assigned to E. macrospondylus by Koken. The taxon was established for the distinctive the atlas-axis morphology, in particular the apparent lack of an axis parapophysis. Enaliosuchus macrospondylus has been considered a valid taxon in recent studies, based upon a largely complete metriorhynchid specimen from the Valanginian of France that had been referred to this taxon, an assignment that has never been questioned. Here we provide a detailed re-description of the E. macrospondylus holotype specimen and determine whether it is diagnostic, and if a referral of the French specimen to E. macrospondylus is justified. We also discuss whether E. macrospondylus and another metriorhynchid specimen from the Valanginian of northern Germany, described as Enaliosuchus schroederi , are conspecific. Finally, we provide an overview of the current knowledge of metriorhynchid diversity during the Cretaceous. [ABSTRACT FROM AUTHOR]