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We report here finds of thalattosuchians from Western Carpathians. The material consists of two isolated teeth from two different localities of the Pieniny Klippen Belt. The material represents the first evidence of the occurrence of both clades Teleosauridae and Metriorhynchidae in Slovakia. The first, a small tooth comes from the locality Beňatina and is dated early Middle Jurassic (Aalenian). Identification of the specimen shows it belongs to a longirostrine teleosaurid, possibly to Steneosaurus. Teleosaurids were largely restricted to lagoonal/near-shore environments. Their limbs allow them to support and walk on land. Regarding that fact, the presence of this taxon in Beňatina might be an indication of terrestrial land in the nearby area and shows a location of epicontinental seaways. A second larger tooth was found in the Upper Jurassic (Tithonian) sediments of the locality Kyjov, and is tentatively allocated in the genus Plesiosuchus. The members of Plesiosuchina are known in England, Franc...

Teleosauridae and Metriorhynchidae were thalattosuchian crocodylomorph clades that secondarily adapted to marine life and coexisted during the Middle to Late Jurassic. While teleosaurid diversity collapsed at the end of the Jurassic, most likely as a result of a global cooling of the oceans and associated marine regressions, metriorhynchid diversity was largely unaffected, although the fossil record of Thalattosuchia is poor in the Cretaceous. In order to investigate the possible differences in thermophysiologies between these two thalattosuchian lineages, we analysed stable oxygen isotope compositions (expressed as δ18O values) of tooth apatite from metriorhynchid and teleosaurid specimens. We then compared them with the δ18O values of coexisting endo-homeothermic ichthyosaurs and plesiosaurs, as well as ecto-poikilothermic chondrichthyans and osteichthyans. The distribution of δ18O values suggests that both teleosaurids and metriorhynchids had body temperatures intermediate between those of typical ecto-poikilothermic vertebrates and warm-blooded ichthyosaurs and plesiosaurs, metriorhynchids being slightly warmer than teleosaurids. We propose that metriorhynchids were able to raise their body temperature above that of the ambient environment by metabolic heat production, as endotherms do, but could not maintain a constant body temperature compared with fully homeothermic ichthyosaurs and plesiosaurs. Teleosaurids, on the other hand, may have raised their body temperature by mouth-gape basking, as modern crocodylians do, and benefited from the thermal inertia of their large body mass to maintain their body temperature above the ambient one. Endothermy in metriorhynchids might have been a by-product of their ecological adaptations to active pelagic hunting, and it probably allowed them to survive the global cooling of the Late Jurassic, thus explaining the selective extinction affecting Thalattosuchia at the Jurassic–Cretaceous boundary.This article is part of the theme issue ‘Vertebrate palaeophysiology'.

Metriorhynchidae is an extinct group of Jurassic–Cretaceous crocodylomorphs that developed a fully pelagic lifestyle. Its Jurassic record is outstanding (it includes around 40 nominal species), while the records that can be restricted to the Cretaceous are particularly sparse. Here we describe a partial skull of a new species of Cricosaurus, Cricosaurus puelchorum sp. nov., from the lower Berriasian of the Vaca Muerta Formation (Neuquen Basin, Argentina). The description of the specimen reveals a series of autapomorphies and a unique combination of characters that justify the creation of a new species. Phylogenetic analysis places Cricosaurus puelchorum sp. nov. closer to three upper Kimmeridgian–lower Tithonian species of southern Germany. The new taxon was recovered in connection with an accurate ammonoid-based biostratigraphic control and allows confirming the survival of Cricosaurus across the J/K boundary at the southeastern Pacific., Facultad de Ciencias Naturales y Museo

IGM 9026 is a singular fossil collected at the beginning of the 20th century in an improperly documented site within the Tlaxiaco Basin, near to Tlaxiaco town, Oaxaca, Mexico. The age of the site was suggested as being early Cretaceous. This specimen is the holotype of Plesiosaurus (Polypticodon) mexicanus, which later was identified as a possible late Jurassic marine crocodylomorph of the family Metriorhynchidae, and consequently it was referred as ?Cricosaurus mexicanus. The present study provides a re-description of this fossil based on a microscopic analysis and the use of white and UV lights; these analyses led to the discovery of peculiar dental characters diagnostic of the genus Torvoneustes. This finding supports the re-classification of IGM 9026 under a new nominal combination as Torvoneustes mexicanus. Along the Tlaxiaco Basin, the fossil preservation mode and lithological composition observed in IGM 9026 only occur in the marine vertebrates recently discovered in Yosobé, a Kimmeridgian shale outcrop characterized by clay calcareous nodules that belong to the Sabinal Formation, near Tlaxiaco town. This peculiarity suggests that T. mexicanus could represent an additional element of the Kimmeridgian vertebrate assemblage recovered in this geological unit. The two nominal species of Torvoneustes were collected in Kimmeridgian marine deposits of England; hence, this finding expands the geographical distribution of Torvoneustes all along the Tethys Sea, from its Eastern/European to western/Caribbean domains., Facultad de Ciencias Naturales y Museo

Metriorhynchidae is a family of highly specialized, extinct marine crocodylomorphs that inhabited the Paleopacific Ocean and the Tethys Sea during the Jurassic and the Early Cretaceous. Numerous metriorhynchid fossil specimens have been recovered from European and South American localities, but North American records of this family are still scarce. Here, we describe a recently recovered Kimmeridgian metriorhynchid from the Sabinal Formation, Tlaxiaco Basin, Oaxaca, Mexico, that is attributable to the genus Maledictosuchus. This genus was known previously from a single species, M. riclaensis, from the Middle Jurassic of Spain. The characteristics of this Mexican specimen support its identification as a new species, Maledictosuchus nuyivijanan, sp. nov. The two species differ in dental and skull-roof morphology. The frontal of M. nuyivijanan, sp. nov., has a wide, rounded anterior end that extends rostrally to the same level of the anterior end of the prefrontal, whereas the frontal of M. riclaensis has a narrow anterior end that is located posterior to the anterior end of the prefrontal. Additionally, the teeth of M. nuyivijanan, sp. nov., exhibit bicarinated crowns, a smooth labial surface, and a lingual surface ornamented with longitudinal ridges, whereas those of M. riclaensis lack carinae and the labial and lingual surfaces are covered with considerably more conspicuous ridges. The North American occurrence of M. nuyivijanan, sp. nov., suggests a wider temporal and geographic distribution for the genus Maledictosuchus across the Tethys Sea than previously thought: from the Callovian in Europe to the Kimmeridgian in southern North America. Fil: Barrientos-Lara, Jair Israel. Universidad Nacional Autónoma de México. Instituto de Geología; México Fil: Alvarado-Ortega, JesÚs. Universidad Nacional Autónoma de México. Instituto de Geología; México Fil: Fernández, Marta Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina

Here we describe an isolated tooth of a metriorhynchid crocodylomorph from the Hybla Formation (Aptian, Lower Cretaceous) of Rocca Chi Parra quarry (Montagna Grande, Calatafimi, Trapani Province), Sicily, Italy. The specimen shares with the Upper Jurassic taxon Plesiosuchus manselii a mediolaterally compressed conical tooth crown, noticeable lingual curvature, mesial and distal carinae with microscopic, rectangular contiguous denticles, strong distal curvature of the mesial margin, and the presence of weak 'carinal flanges' on the labial and lingual surfaces (which are preeminent at the mid-crown). This suite of morphologies is also present in an unnamed Valanginian (Lower Cretaceous) plesiosuchinan from France. However, the Sicilian tooth differs from these taxa in having more pronounced carinae, and faint apicobasally aligned enamel ridges. It also differs from P. manselii in having more extensive 'carinal flanges' on the labial surface. The specimen extends the known geological range of Metriorhynchidae and Thalattosuchia by approximately 7–8 million years. This overturns previous hypotheses of Metriorhynchidae becoming extinct early in the Early Cretaceous.

Morphological and physiological features indicate Metriorhynchidae as the only group of crocodylomorphs with a pelagic lifestyle. Some of these features have evolved convergently in several clades of tetrapods secondarily adapted to aquatic life. One striking feature of metriorhynchids as compared to other crocodylomorphs is the morphology of the pelvic region (i.e., ventrally deflected sacral ribs and reduced pelvic girdle), which increases significantly the depth of this region. This morphology, as a whole, resembles that of other viviparous Mesozoic marine reptiles not phylogenetically related to metriorhynchids. We tested two alternative hypotheses of reproductive strategies in this clade: oviparity vs. viviparity. Given the lack of direct evidence supporting one or the other, we explored the use of evidence that may disconfirm either of these hypotheses. Using this counter-inductive approach, we found no cases contradicting viviparity in metriorhynchids, except for their phylogenetic position as archosaurs. A survey of reproductive modes amongst amniotes depicts the evolutionary plasticity of the transition to viviparity, and a widespread occurrence among tetrapods secondarily adapted to a marine life. Assuming oviparity for metriorhynchids implies egg-laying out of the water. However, their postcranial morphology (i.e., features of fore and hind limbs, pelvic girdle, and tail) contradicts this possibility. In this context, we rejected oviparity for metriorhynchids., Facultad de Ciencias Naturales y Museo

Fossil records of Geosaurini taxa in South American margins of the Eastern Pacific are scarce. We describe a new specimen of Geosaurini found in sedimentites of the Vaca Muerta Formation (Substeueroceras koeneni Biozone, uppermost Tithonian-lowermost Berriasian) and referred it as Dakosaurus cf. D. andiniensis. The close stratigraphic association of this specimen with late Tithonian to early Berriasian ammonoids allows confirming with biostratigraphic accuracy that, up to date, the first known occurrence of the Geosaurini taxa in South American is in late Tithonian. The specimen consists of a partially preserved skull and a partially exposed natural endocast of the brain cavity, which is the first detailed description of a natural endocast of a metriorhynchid. The conspicuous blood vessel fillings covering almost all the dorsal surface of the cerebral hemispheres suggest that the dural envelope of this region was thin and that the cerebral hemispheres filled most of the cavity. A large dorsal venous sinus that overlays the dorsal region of the hindbrain, a tube-like cavity connecting the cranioquadrate passage and an enlarged internal carotid canal, previously described for "Metriorhynchus" cf. "M." westermanni and present in Dakosaurus cf. D. andiniensis, suggest that these features were more widely distributed within metriorhynchids. Fil: Herrera, Laura Yanina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Vennari, Verónica Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina

A new metriorhynchid crocodylomorph from the Lower Kimmeridge Clay Formation (Kimmeridgian, Upper Jurassic) of England is described. This specimen, a three-dimensionally preserved skull and left mandibular ramus, is referred to a new species: Torvoneustes coryphaeus sp. nov. Within the genus Torvoneustes, T. coryphaeus sp. nov. is unique as it has a long anteromedial process of the frontal, ornamented dermatocranium, and the supraorbital notch forms a strongly acute angle. Our phylogenetic analysis confirms the placement of this specimen in Torvoneustes. The dentition of T. coryphaeus sp. nov., like that of the type species, has a blunt apex, crown basal–mid regions with numerous tightly packed apicobasally aligned ridges, and apical region with an anastomosed pattern of ridges that interact with the carinae. Within Thalattosuchia these dental characteristics are only found in Torvoneustes and the teleosaurid Machimosaurus. The heavily ornamented dermatocranium of T. coryphaeus sp. nov. is in contrast to the unornamented (nasals and frontal)–lightly ornamented (maxillae and premaxillae) pattern seen in Torvoneustes carpenteri. Curiously, this pattern of reduction and loss of dermatocranium ornamentation is also observed in Metriorhynchus, Dakosaurus, and the subclade Rhacheosaurini. We hypothesize that the ‘smooth’ dermatocranium of Late Jurassic metriorhynchids evolved independently in each subclade (parallel evolution), and would have reduced drag, thereby making locomotion through water more energy efficient. © 2013 The Linnean Society of London

Upper Jurassic (Tithonian) deposits in north-western Patagonia, Argentina, have yielded rich and taxonomically diverse assemblages of marine reptiles. These assemblages are also remarkable by their quality of preservation and are represented by ichthyosaurs, plesiosaurs, turtles and crocodyliforms. Despite the abundant crocodyliform record, only two metriorhynchid taxa have been identified: Cricosaurus araucanensis and Dakosaurus andiniensis. Here we described a new species of Cricosaurus, which represents the second species of Cricosaurus in the Tithonian of the Neuquen Basin, and the first metriorhynchid found in lithographic limestone from Gondwana. Furthermore, this specimen has the most complete postcranial remains of any metriorhynchid from South America. The new species is characterized by a short distance between the premaxilla and the nasal, a relatively narrow interorbital width, 23–25 mandibular teeth, bicarinated teeth with fine apicobasally aligned ridges, interalveolar spaces between the first seven teeth approximately 1.5 times longer than the anteroposterior diameter of the respective alveoli. To test the assignment of the new species to Cricosaurus, we carried out two phylogenetic analyses. In both analyses, Cricosaurus lithographicus sp. nov. is nested with other species referred to this genus. This new species has peculiar enamel ornamentation, characterized by numerous, fine apicobasally aligned ridges, when compared to other species of the genus.

The antorbital fenestra of Metriorhynchidae (Crocodyliformes, Thalattosuchia): Testing Its homology within a phylogenetic framework Juan Martin Leardi a , Diego Pol b & Marta S. Fernandez c a CONICET, IDEAN, Departamento de Ciencias Geologicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Guiraldes 2160, Ciudad Universitaria (C1428RGA), Buenos Aires, Argentina b CONICET, Museo Paleontologico Egidio Feruglio, Av. Fontana 140 (9100), Trelew, Chubut, Argentina c CONICET, Departamento de Paleontologia Vertebrados, Museo de La Plata, Paseo del Bosque s/n (1900) La Plata, Buenos Aires, Argentina

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. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 163, 1199–1216.

Metriorhynchids have been interpreted as the only archosaurs entirely adapted to pelagic marine life, given the deep morphological modifications of their skeletons. The most conspicuous feature in the skull involves the “fenestra and fossa antorbitalis complex.” Exceptionally preserved natural cast of snout cavities of Geosaurus araucanensis, found in the Late Jurassic of the Neuquen Basin (northwestern Patagonia, Argentina), allow exploration of the rostral anatomy of this metriorhynchid. The presence of a paranasal sinus system, hypothetically reconstructed by other authors using EPB method approach, can now be confirmed based on direct morphological evidence. We propose that the openings classically identified in the literature as internal and external antorbital fenestrae of metriorhynchid have been misidentified; the preorbital opening of metriorhynchids is a neomorph associated with a novel salt gland that evolved independent of the antorbital fenestra, and that the true antorbital cavity o...

Synopsis New information on Dakosaurus andiniensis from the Latest Jurassic and Early Cretaceous is reported here. One of the specimens described herein consists of an almost complete skull and lower jaw found in the uppermost levels of the Vaca Muerta Formation (Tithonian) of Neuquen Province, Argentina. The new material allows a more complete understanding and diagnosis of this form, previously known only from the fragmentary type specimen. The new remains show that D. andiniensis had an unusual morphology for a marine crocodyliform,namely a remarkably short, high snout with ziphodont dentition. This new information allows testing of the phylogenetic relationships of this taxon, which is depicted as deeply nested within Metriorhynchidae, a clade of marine crocodyliforms with derived adaptations to the marine environment (e.g. paddle‐like forelimbs, hypertrophied nasal salt glands). In particular, D. andiniensis is inferred to be the sister taxon of D. maximus from the Jurassic of Europe. This relationsh...

Several Teleosaurus skulls were described during the nineteenth century. Unfortunately, all skulls from this genus were destroyed during World War II. The only available skull is currently preserved in the MNHN. Thanks to a new preparation, new anatomical features can be seen, such as the morphology of the nasal cavity, the external otic recess, and the distribution of the foramina for the cranial nerves. A phylogenetic analysis is presented, including 14 thalattosuchian taxa. This analysis has generated four equally most parsimonious trees, where the thalattosuchians are closely related to the pholidosaurids and dyrosaurids, forming a longirostrine taxa. These relationships have been often considered to be based on homoplasies, related to the longirostrine morphology. This is also suggested herein, as the deletion of the longirostrine dependant characters or of the most longirostrine thalattosuchians in the analysis provide a consensus tree where thalattosuchians are basal crocodyliforms, a resu...

Metriorhynchidae was the only Crocodylomorpha with a pelagic marine lifestyle. Related to this lifestyle, its peculiar body plan al- lows clearly differentiate them from others Crocodylomorpha. The fossil record of metriorhynchids from Tithonian–Berriasian levels of the Vaca Muerta Formation (Neuquén Basin, Argentina) is outstanding, in terms of quantitative and qualitative record. Its taxonomical diversity is composed by four taxa: Cricosaurus araucanensis, Cricosaurus lithographicus, Dakosaurus andiniensis, and Purranisaurus potens. This fossil record is also characterized by the tridimensional preservation of the materials and by the preservation of numerous natural endocasts of the skull cavities. Here, I made a description of the natural endocasts of the brain of Cricosaurus araucanensis together with a synthesis of the advances in the knowledge of these four taxa that were performed during the last years. The information that provides the endocasts, to- gether with the quantity of endocasts, make of the Patagonian fossil record of metriorhynchids a key to the exploration and reconstruction of soft anatomy of these crocodylomorphs, and for the understanding of the physiological changes that accompanied the structural changes of the skeleton. Understanding these changes will allow defining the key innovations that allowed to the metriorhynchids conquer the pelagic environment, unparalleled among archosaurs., Los Metriorhynchidae fueron los únicos Crocodylomorpha con un estilo de vida marino pelágico. Relacionado con este estilo de vida, su peculiar plan corporal permite diferenciarlos claramente de los demás Crocodylomorpha. El registro fósil de los metriorrínquidos titonienses–berriasienses de la Formación Vaca Muerta (Cuenca Neuquina, Argentina) es excepcional, tanto en términos cuantitativos como cualitativos. Su diversidad taxonómica está compuesta por cuatro taxones: Cricosaurus araucanensis, Cricosaurus lithographicus, Dakosaurus andiniensis y Purranisaurus potens. Este registro fósil también se caracteriza por la preservación tridimensional de los materiales y por la preservación de numerosos moldes naturales de las cavidades del cráneo. En este trabajo se presenta una descripción de los moldes naturales del encéfalo de Cricosaurus araucanensis junto con una síntesis de los avances en el conocimiento realizados, en los últimos años, sobre estos cuatro taxones argentinos. La calidad de la información que aporta los moldes naturales, sumado a la cantidad de moldes recuperados, hacen del registro patagónico una pieza clave para la exploración y reconstrucción de la anatomía blanda de estos crocodilomorfos, y para la comprensión de los cambios fisiológicos que acompañaron los cambios estructurales del esqueleto. La comprensión de estos cambios permitirá delimitar las innovaciones evolutivas claves que le permitieron a los metriorrínquidos la conquista, sin paralelo entre los arcosaurios, del medio pelágico., Facultad de Ciencias Naturales y Museo

The thalattosuchian crocodyliform Pelagosaurus typus Bronn, 1841 is fully documented and described from the Upper Lias (Toarcian, Lower Jurassic) of England. The material under study is part of a historical collection made by Charles Moore (1814–1881) at Strawberry Bank (Ilminster, Somerset, England) around 1848. Apomomorphic features of the genus include: sculpturing on almost the entire skull and mandible with extensive sculpturing on the prefrontal, lachrymal, frontal, parietal, temporal arcade and the posterior extent of the mandible; 30 piercing teeth on each side of the upper and lower jaws; small, shallow, egg-shaped antorbital fenestra present within the lachrymal and maxilla; supratemporal fenestrae short anteroposteriorly; paired frontal; anterior margin of internal choana tapers anteriorly between the paired palatines; and presence of a choanal septum on the palatine and pterygoid. Pelagosaurus was a small, exceedingly long-snouted, gracile crocodyliform whose diet probably consisted o...

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.

Remains of the marine crocodyliform Dakosaurus andiniensis from western South America reveal a lineage that drastically deviated from the skull morphology that characterizes marine crocodyliforms. The snout and lower jaw are extremely robust, short, and high and only bear a few large teeth with serrated edges (resembling those of some terrestrial carnivorous archosaurs). This unusual morphology contrasts with the long and gracile snout and lower jaws bearing numerous teeth, which are present in the closest relatives of D. andiniensis (and interpreted as indicating feeding on small fish or mollusks). Thus, the morphological diversity of pelagic marine crocodyliforms was wider than had been thought. Fil: Brandoni, Zulma Nelida. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina Fil: Pol, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Ohio State University; Estados Unidos Fil: Spalletti, Luis Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Centro de Investigaciones Geológicas. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Centro de Investigaciones Geológicas; Argentina

Thalattosuchian crocodilians of the genus Geosaurus have mostly been recorded from the Jurassic of Europe. A single species was reported from Argentina. Here we describe a new species of Geosaurus vignaudi from the middle Tithonian La Pimienta Formation of State of Puebla, Mexico. Diagnostic for this species are the extremely low tooth count and a rostroventrally directed process at the rostral terminus of the mandible combined with a pair of horizontally directed rostral teeth. The skull of the holotype shows bite marks that probably caused the death of the animal. Resume : Jusqu'a present, les crocodiles thalattosuchiens du genre Geosaurus proviennent surtout des sediments jurassi- ques d'Europe. Une seule espece est connue hors d'Europe, en Argentine. Nous decrivons ici une nouvelle espece du genre Geosaurus vignaudi provenant du Tithonien moyen de la formation La Pimienta, etat de Puebla, Mexique. Le nombre tres reduit de dents, et un processus dirige rostroventralement a l'extremite rostrale de la mandibule associe a une paire de dents rostrales horizontales, sont diagnostiques de l'espece. Le crâne du specimen porte des traces de morsures, qui ont probablement cause la mort de l'animal.

Resume Un squelette axial sub-complet d'Enaliosuchus macrospondylus Koken , 1883 (Crocodylia, Metriorhynchidae) a ete decouvert dans le Valanginien inferieur (zone a Campylotoxus) de la region de Barret-le-Bas (Hautes Alpes). Ce squelette est le plus complet et le mieux cale stratigraphiquement appartenant a ce genre. Seuls deux autres specimens plus fragmentaires sont connus. Cet animal represente l'un des tout derniers Metriorhynchidae connus. Il presente un cas unique de remontee des narines externes chez un crocodilien, caractere inconnu jusque la dans ce taxon.

In 1787, a fragmentary fossil skull of a crocodylian was discovered in the Altopiano dei Sette Comuni (Veneto, Northern Italy). In 1883, the specimen was referred to a new species of the teleosauroid Steneosaurus, S. barettoni. In this study, the specimen is redescribed and its taxonomic status reviewed. S. barettoni fails to conform to Article 12 of the International Code of Zoological Nomenclature and is considered as a nomen nudum. The specimen lacks synapomorphies of both Teleosauroidea and Steneosaurus, whereas it is referred to Metriorhynchidae based on the presence of an elongate median depression between the dorsal surface of nasals, and a large teardrop-shaped prefrontal that is expanded laterally. The combination of cranial and dental features present in this specimen supports its referral to Neptunidraco, an interpretation that adds new information on the morphology of the Italian metriorhynchid. Although total evidence analysis placed Neptunidraco as a basal divergence among Geosaurinae, it independently evolved some craniomandibular features previously considered exclusive of the macrophagous Geosaurini. This specimen is historically relevant because it may represent the first metriorhynchoid found worldwide.

Young, Mark T., Andrade, Marco Brandalise De, Etches, Steve, Beatty, Brian L. (2013): A new metriorhynchid crocodylomorph from the Lower Kimmeridge Clay Formation (Late Jurassic) of England, with implications for the evolution of dermatocranium ornamentation in Geosaurini. Zoological Journal of the Linnean Society 169 (4): 820-848, DOI: 10.1111/zoj.12082, URL: http://dx.doi.org/10.1111/zoj.12082

Upper Jurassic (Tithonian) deposits in north-western Patagonia, Argentina, have yielded rich and taxonomically diverse assemblages of marine reptiles. These assemblages are also remarkable by their quality of preservation and are represented by ichthyosaurs, plesiosaurs, turtles and crocodyliforms. Despite the abundant crocodyliform record, only two metriorhynchid taxa have been identified: Cricosaurus araucanensis and Dakosaurus andiniensis. Here we described a new species of Cricosaurus, which represents the second species of Cricosaurus in the Tithonian of the Neuque´n Basin, and the first metriorhynchid found in lithographic limestone from Gondwana. Furthermore, this specimen has the most complete postcranial remains of any metriorhynchid from South America. The new species is characterized by a short distance between the premaxilla and the nasal, a relatively narrow interorbital width, 23–25 mandibular teeth, bicarinated teeth with fine apicobasally aligned ridges, interalveolar spaces between the first seven teeth approximately 1.5 times longer than the anteroposterior diameter of the respective alveoli. To test the assignment of the new species to Cricosaurus, we carried out two phylogenetic analyses. In both analyses, Cricosaurus lithographicus sp. nov. is nested with other species referred to this genus. This new species has peculiar enamel ornamentation, characterized by numerous, fine apicobasally aligned ridges, when compared to other species of the genus. Fil: Herrera, Yanina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina Fil: Brandoni, Zulma Nelida. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Fernández, Marta Susana. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The histological study of various bones in the families Teleosauridae and Metriorhynchidae reveals common, but also contrasting structural features of the skeleton. Both display a zonal pattern of bone tissue, suggesting a cyclic growth and an ecto-poikilothermic physiology, quite similar to those of recent crocodiles. However, the Teleosauridae exhibit no peculiar skeletal specializations related to marine life, which suggests that they had an amphibious, rather than a truly marine habitat. Conversely, the skeleton of the Metriorhynchidae displays a certain degree of structural lightening, especially obvious in their skull, but also present in their femora and ribs. This structural specialization of the skeleton, together with the supposed physiological regime of the Metriorhynchidae, had definite bearings on their body trim in water, locomotor capabilities, and activity cycles. These various topics are discussed with reference to the ecological and eco-physiological adaptations of the Thalattos...

Closure of neurocentral sutures in the crocodylian vertebral column follows a distinct caudal to cranial sequence during ontogeny. The sutures in most caudal vertebrae are fully closed at hatching, but closure of remaining sutures occurs later in ontogeny. Closure of cervical sutures is a consistent indicator of morphological maturity in Alligator mississippiensis, Alligator sinensis, Osteolaemus tetraspis, and Crocodylus acutus; the final transformation is the closure of the axial neurocentral suture, which occurs after the closure of the axis-odontoid suture. Because these transformations occur near the end of ontogeny in all three taxa, regardless of maximum size, closure of these sutures is a size-independent criterion of maturity; however, it is not certain if suture closure indicates the stoppage of growth. These transformations are readily identifiable in fossils, permitting the objective characterization of maturity in fossil crocodylians and possibly at least some of their closer extinct...

Teleosauridae was a group of largely marine Mesozoic crocodylomorphs, typically considered as akin to “marine gavials” due to their elongate, tubular, polydont rostra that are indicative of a piscivorous diet. Here we show that these extinct crocodylomorphs were more anatomically, and perhaps ecologically, varied than previously thought. We report the first evidence of denticles in a teleosaurid tooth, revealed by scanning electron microscopic (SEM) analysis of a tooth from the holotype of “Steneosaurus” obtusidens. These denticles are cryptic, because they are microscopic, not contiguous along the carinae (instead forming short series), and are detectable only using SEM. This incipient denticle morphology is similar to that recently discovered in a closely related group of marine crocodylomorphs, the Metriorhynchidae. In particular, the denticulation morphology of “Steneosaurus” is similar to that of the geosaurin metriorhynchid Torvoneustes, indicating that these two taxa may have employed similar feeding styles and that “S.”obtusidens may have been a nearshore ecological analogue to the more offshore, fast-swimming geosaurins. Previous authors have considered “S.” obtusidens and Machimosaurus to be durophagous, but the discovery of denticulated teeth indicates that they had a more varied diet and feeding style, and included flesh slicing as part of their feeding toolkit. It is currently unknown how extensive denticulate carinae may be in Teleosauridae, and we hypothesise that cryptic denticles may also be present in other marine crocodylomorphs once they are subjected to SEM study.

The metriorhynchid crocodyliform Cricosaurus araucanensis (Gasparini & Dellapé) has been documented from Tithonian (Upper Jurassic) strata of the Vaca Muerta Formation exposed in the Neuquén Basin, northwest Patagonia, Argentina. Postcranial components of this species were mentioned but not described in the original analysis. Subsequently, other authors described the forelimbs. The postcranial elements of metriorhynchids are poorly documented in comparison with their skulls, but new data from C. araucanensis reveal delayed ossification of the caudal neurocentral sutures indicating skeletal paedomorphosis affecting not only the appendicular skeleton but also the posterior region of the vertebral column. The morphology of the caudal region (transverse processes of the first caudal vertebrae ventrally deflected) and the reduction in the femur of the fourth trochanter suggest a reduction of the hypaxial musculature allowing increased epaxial musculature. This pattern of musculoskeletal arrangement is consistent with the swimming style and propulsion by lateral undulation of the tail, as proposed by previous authors. Fil: Herrera, Laura Yanina. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Fernández, Marta Susana. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Brandoni, Zulma Nelida. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

BackgroundMarine 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.Methodology/principal findingsHere we present a comprehensive description for this specimen and in doing so we refer it to a new genus and species: Maledictosuchus riclaensis. This species is diagnosed by numerous autapomorphies, including: heterodont dentition; tightly interlocking occlusion; lachrymal anterior process excludes the jugal from the preorbital fenestra; orbits longer than supratemporal fenestrae; palatine has two non-midline and one midline anterior processes. Our phylogenetic analysis finds Maledictosuchus riclaensis to be the basal-most known member of Rhacheosaurini (the subclade of increasingly mesopelagic piscivores that includes Cricosaurus and Rhacheosaurus).Conclusions/significanceOur description of Maledictosuchus riclaensis shows that the craniodental morphologies that underpinned the success of Rhacheosaurini in the Late Jurassic and Early Cretaceous, as a result of increasing marine specialization to adaptations for feeding on fast small-bodied prey (i.e. divided and retracted external nares; reorientation of the lateral processes of the frontal; elongate, tubular rostrum; procumbent and non-carinated dentition; high overall tooth count; and dorsolaterally inclined paroccipital processes), first appeared during the Middle Jurassic. Rhacheosaurins were curiously rare in the Middle Jurassic, as only one specimen of Maledictosuchus riclaensis is known (with no representatives discovered from the well-sampled Oxford Clay Formation of England). As such, the feeding/marine adaptations of Rhacheosaurini did not confer an immediate selective advantage upon the group, and it took until the Late Jurassic for this subclade to dominate in Western Europe.

Re-description of a long-known, but little studied, metriorhynchid crocodylomorph from the Oxfordian of England begins to help fill the ‘Corallian Gap’. This ‘Gap’ represents a paucity of vertebrate remains from the Oxfordian of England. Filling the ‘Corallian Gap’ has important implications for our understanding of metriorhynchids from England, especially as there was a shift in this ecosystem from being metriorhynchine dominated in the older Oxford Clay Formation, to a geosaurine-dominated fauna in the younger Kimmeridge Clay Formation. The re-description of the specimen reveals that it is a member of the derived subclade Geosaurini, which most likely pertains to the genus Torvoneustes.

Metriorhynchidae was a peculiar but long-lived group of marine Mesozoic crocodylomorphs adapted to a pelagic lifestyle. Recent discoveries show that metriorhynchids evolved a wide range of craniodental morphotypes and inferred feeding strategies. One genus, Dakosaurus, is arguably the most aberrant marine crocodylomorph due to its large, robust, ziphodont teeth; very low tooth count; and brevirostrine/oreinirostral snout. We here report an additional unusual feature of Dakosaurus that is unique among marine crocodylomorphs: tightly fitting tooth-to-tooth occlusion, whose inference is supported by reception pits along the upper and lower tooth rows, indicative of vertically orientated crowns that were in close contact during occlusion, and three distinct types of dental wear. These include irregular spalled surfaces near the apex (probably caused by tooth-food contact), semi-circular wear near the base, and elongate surfaces extending along the mesial and distal margins of the teeth, obliterating the carinae (including the denticles). Scanning electron micrographs show that these latter surfaces are marked by parallel apicobasal striations, which in extant mammals reflect tooth-tooth contact. As such, we interpret the carinal wear facets in Dakosaurus as being formed by repeated tooth-tooth contact between the mesial and distal margins of the teeth of the upper and lower jaw. We posit that this increased the available shearing surface on their high crowns. Together, these wear patterns suggest that occlusion in Dakosaurus was specialized for cutting large and abrasive prey items into portions small enough to swallow, making it a prime example of an aquatic reptile with macrophagous feeding habits. © 2012 Wiley-Periodicals, Inc. Fil: Young, Mark T.. University of Glasgow; Reino Unido. University of Edinburgh; Reino Unido Fil: Brusatte, Stephen L.. Columbia University In The City Of New York; . American Museum of Natural History; Estados Unidos Fil: Beatty, Brian L.. New York College Of Osteopathic Medicine, Old Westbury; Fil: Brandalise de Andrade, Marco. Universidade Federal do Rio Grande do Sul; Brasil Fil: Desojo, Julia Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina

Background: Dakosaurus and Plesiosuchus are characteristic genera of aquatic, large-bodied, macrophagous metriorhynchid crocodylomorphs. Recent studies show that these genera were apex predators in marine ecosystems during the latter part of the Late Jurassic, with robust skulls and strong bite forces optimized for feeding on large prey. Methodology/Principal Findings: Here we present comprehensive osteological descriptions and systematic revisions of the type species of both genera, and in doing so we resurrect the genus Plesiosuchus for the species Dakosaurus manselii. Both species are diagnosed with numerous autapomorphies. Dakosaurus maximus has premaxillary 'lateral plates'; strongly ornamented maxillae; macroziphodont dentition; tightly fitting tooth-to-tooth occlusion; and extensive macrowear on the mesial and distal margins. Plesiosuchus manselii is distinct in having: non-amblygnathous rostrum; long mandibular symphysis; microziphodont teeth; tooth-crown apices that lack spalled surfaces or breaks; and no evidence for occlusal wear facets. Our phylogenetic analysis finds Dakosaurus maximus to be the sister taxon of the South American Dakosaurus andiniensis, and Plesiosuchus manselii in a polytomy at the base of Geosaurini (the subclade of macrophagous metriorhynchids that includes Dakosaurus, Geosaurus and Torvoneustes). Conclusions/Significance: The sympatry of Dakosaurus and Plesiosuchus is curiously similar to North Atlantic killer whales, which have one larger 'type' that lacks tooth-crown breakage being sympatric with a smaller 'type' that has extensive crown breakage. Assuming this morphofunctional complex is indicative of diet, then Plesiosuchus would be a specialist feeding on other marine reptiles while Dakosaurus would be a generalist and possible suction-feeder. This hypothesis is supported by Plesiosuchus manselii having a very large optimum gape (gape at which multiple teeth come into contact with a prey-item), while Dakosaurus maximus possesses craniomandibular characteristics observed in extant suction-feeding odontocetes: shortened tooth-row, amblygnathous rostrum and a very short mandibular symphysis. We hypothesise that trophic specialisation enabled these two large-bodied species to coexist in the same ecosystem., Facultad de Ciencias Naturales y Museo

Metriorhynchid crocodylomorphs were the only group of archosaurs to fully adapt to a pelagic lifestyle. During the Jurassic and Early Cretaceous, this group diversified into a variety of ecological and morphological types, from large super-predators with a broad short snout and serrated teeth to specialized piscivores/teuthophages with an elongate tubular snout and uncarinated teeth. Here, we use an integrated repertoire of geometric morphometric (form), biomechanical finite-element analysis (FEA; function) and phylogenetic data to examine the nature of craniofacial evolution in this clade. FEA stress values significantly correlate with morphometric values representing skull length and breadth, indicating that form and function are associated. Maximum-likelihood methods, which assess which of several models of evolution best explain the distribution of form and function data on a phylogenetic tree, show that the two major metriorhynchid subclades underwent different evolutionary modes. In geosaurines, both form and function are best explained as evolving under ‘random’ Brownian motion, whereas in metriorhynchines, the form metrics are best explained as evolving under stasis and the function metric as undergoing a directional change (towards most efficient low-stress piscivory). This suggests that the two subclades were under different selection pressures, and that metriorhynchines with similar skull shape were driven to become functionally divergent.

A three-dimensionally preserved metriorhynchid braincase from the Oxfordian of northern Chile is described. The specimen is referred to the metriorhynchid Metriorhynchus cf.M. westermanni. The excellent preservation provides clear sutures and a detailed description, and X-ray computed tomographic (CT) scanning provides internal anatomical details. The general pattern of the orbitotemporal region is consistent with that of the basal thalattosuchian Pelagosaurus typus as described recently. The specimen from northern Chile shares with other metriorhynchids (e.g., Cricosaurus araucanensis, Metriorhynchus westermanni, M. casamiquelai, and Dakosaurus andiniensis) a dorsally exposed laterosphenoid, a laterosphenoidprootic suture forming a blunt crest separating the supratemporal fenestra into two fossae for muscular attachment, and the quadrate incompletely sutured to the braincase. Thus, these features characterize not only basal but derived Thalattosuchia, as suggested by previous authors. The main difference in the orbitotemporal region is that in the specimen described herein, and in the other metriorhynchids examined, the trigeminal fossa is developed mainly caudal to the trigeminal foramen, whereas in P. typus the fossa is developed rostral and caudal to the trigeminal foramen. CT scanning indicates the presence of enlarged dorsal dural venous sinuses overlying the brain, as it has been described recently in Steneosaurus pictaviensis, and a well-developed sinus within the quadrate. The large foramen ventrolateral to the occipital condyle, which characterizes metriorhynchids, is confirmed as the entry for the internal carotid artery.Metriorhynchus cf.M. westermanni. The excellent preservation provides clear sutures and a detailed description, and X-ray computed tomographic (CT) scanning provides internal anatomical details. The general pattern of the orbitotemporal region is consistent with that of the basal thalattosuchian Pelagosaurus typus as described recently. The specimen from northern Chile shares with other metriorhynchids (e.g., Cricosaurus araucanensis, Metriorhynchus westermanni, M. casamiquelai, and Dakosaurus andiniensis) a dorsally exposed laterosphenoid, a laterosphenoidprootic suture forming a blunt crest separating the supratemporal fenestra into two fossae for muscular attachment, and the quadrate incompletely sutured to the braincase. Thus, these features characterize not only basal but derived Thalattosuchia, as suggested by previous authors. The main difference in the orbitotemporal region is that in the specimen described herein, and in the other metriorhynchids examined, the trigeminal fossa is developed mainly caudal to the trigeminal foramen, whereas in P. typus the fossa is developed rostral and caudal to the trigeminal foramen. CT scanning indicates the presence of enlarged dorsal dural venous sinuses overlying the brain, as it has been described recently in Steneosaurus pictaviensis, and a well-developed sinus within the quadrate. The large foramen ventrolateral to the occipital condyle, which characterizes metriorhynchids, is confirmed as the entry for the internal carotid artery. Fil: Fernández, Marta Susana. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Paulina Carabajal, Ariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Provincia del Neuquén. Municipalidad de Plaza Huincul. Museo "Carmen Funes"; Argentina Fil: Brandoni, Zulma Nelida. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina Fil: Chong Díaz, Guillermo. Universidad Católica del Norte; Chile

Metriorhynchids were a peculiar group of fully marine Mesozoic crocodylomorphs. The derived genera Dakosaurus and Geosaurus exhibit a macroevolutionary trend towards extreme hypercarnivory, underpinned by a diverse array of craniodental adaptations, including denticulate serrated (ziphodont) dentition. A comparative analysis of serrations in Metriorhynchidae shows that known Dakosaurus species had conspicuous denticles, in contrast to the microscopic denticles of Geosaurus. A new tooth from the Nusplingen Plattenkalk of Germany provides evidence for a previously unknown large species of Geosaurus. Metriorhynchid specimens from the upper Kimmeridgian-lower Tithonian of Southern Germany show that ziphodont species of Dakosaurus and Geosaurus co-occurred in the Nusplingen and Solnhofen Seas. Although these genera are similarly denticulate, they diverge in overall crown morphology. Therefore, resource/niche partitioning via craniodental differentiation is posited as maintaining two contemporaneous genera of highly predatory metriorhynchids. Additionally, the new generic name Torvoneustes is proposed for "Geosaurus" carpenteri, the only known metriorhynchid with false-ziphodont dentition. A cladistic analysis shows that ziphodont dentition may have evolved independently in Dakosaurus and Geosaurus, or been acquired earlier by their common ancestor and secondarily lost in Torvoneustes and related taxa. Fil: Brandalise de Andrade, Marco. University of Bristol; Reino Unido Fil: Young, Mark T.. University of Bristol; Reino Unido Fil: Desojo, Julia Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Brusatte, Stephen L.. Columbia University; Estados Unidos. American Museum of Natural History; Estados Unidos

Young, Mark T., Brusatte, Stephen L., Ruta, Marcello, Andrade, Marco Brandalise De (2010): The evolution of Metriorhynchoidea (mesoeucrocodylia, thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics. Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 158 (4): 801-859, DOI: 10.1111/j.1096-3642.2009.00571.x, URL: http://dx.doi.org/10.1111/j.1096-3642.2009.00571.x

PURRANISAURUS RUSCONI, 1948 Type species: Purranisaurus potens Rusconi, 1948. Valid species: Purranisaurus casamiquelai (Gasparini & Chong, 1977) comb. nov.; P. potens Rusconi, 1948; Purranisaurus westermanni (Gasparini, 1980) comb. nov. Geological range: Lower Callovian–lower Tithonian. Geographical range: South American endemic (Argentina and Chile). Emended diagnosis: Metriorhynchid thalattosuchian with less than 18 teeth per maxilla, and more than 20 teeth per dentary; all teeth lack carinae; lacks conspicuous ornamentation on the cranial bones; the antorbital fossa is elongate, narrow, and oriented obliquely, and is enclosed by the lacrimal, maxilla, and jugal; the antorbital pseudofenestra is enclosed by the lacrimal, nasal, and maxilla; the supratemporal arch in lateral view is straight; the internal nares opens out posteriorly into the buccal cavity, with the palatines creating an M-shape orientated anteriorly; the maxilla–palatine suture forms a broad U-shape orientated anteriorly; the parocciptal process terminates with a sharp incline dorsolaterally; the squamosal contributes less than 50% to the supratemporal arch., Published as part of Young, Mark T., Brusatte, Stephen L., Ruta, Marcello & Andrade, Marco Brandalise De, 2010, The evolution of Metriorhynchoidea (mesoeucrocodylia, thalattosuchia): an integrated approach using geometric morphometrics, analysis of disparity, and biomechanics, pp. 801-859 in Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) (Zool. J. Linn. Soc.) 158 (4) on page 855, DOI: 10.1111/j.1096-3642.2009.00571.x, http://zenodo.org/record/5438508

RHACHEOSAURUS VON MEYER, 1831 Type species: Rhacheosaurus gracilis Von Meyer, 1831. Holotype: lost; however, two plastotypes survive (of vertebral column and hindlimbs), AMNH FR 4804 and NHM R.3961. Etymology: ‘Spine lizard’. Rhacheos- is the Ancient Greek for backbone or spine, in reference to the holotype, which was a vertebral column with limbs and girdles. Geological range: The lower Tithonian (hybonotum ammonite zone). Geographical range: European endemic (Germany). Emended diagnosis: Metriorhynchid thalattosuchian with procumbent teeth, with no lateromedially compression, lacking carinae; cranial bones smooth, lacking conspicuous ornamentation; rounded almost 90° angle formed by the lateral and medial processes of the frontal; dorsal margin of the supratemporal arcade is lower than the medial process of the frontal; eyes as large as the supratemporal fenestra; infratemporal flange absent; surangular and angular well-developed extending rostrally beyond the orbits; symphysial part of the mandible is low, only about 15-mm high; lateral margin of the prefrontals is rounded; external nares not wholly bifurcated by premaxillary septum; external nares begins just after the first premaxillary alveolus, and does not exceed the first maxillary alveolus; humerus deltopectoral crest absent; hypocercal tail possesses a fleshy upper lobe., Published as part of Young, Mark Thomas & Andrade, Marco Brandalise De, 2009, What is Geosaurus? Redescription of Geosaurus giganteus (Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern, Germany, pp. 551-585 in Zoological Journal of the Linnean Society 157 (3) on page 579, DOI: 10.1111/j.1096-3642.2009.00536.x, http://zenodo.org/record/5443313

LTLIMINOSAURUS [SIC] ROMER, 1966 Type species: Geosaurus giganteus (Von Sömmerring, 1816) Cuvier, 1824 sensu Von Quenstedt, 1852. Valid species: Geosaurus giganteus (Von Sömmerring, 1816) Cuvier, 1824 sensu Von Quenstedt, 1852. Holotype: NHM R.1229, incomplete skull and mandible lacking snout and posterior region. Geosaurus grandis (Wagner, 1858) Von Zittel, 1887 –1890. Holotype: BSPG AS-VI-1, complete skull and mandible. Geosaurus lapparenti (Debelmas & Strannoloubsky, 1957) comb. nov. Holotype: UJF-ID.11847, isolated cranial remains, cervical and caudal vertebrae, pectoral girdle elements. Geosaurus carpenteri (Wilkinson et al., 2008) comb. nov. Holotype: BRSMG Ce17365, incomplete skull. Etymology: ‘Earth lizard’. Ge- is the Ancient Greek for Earth (in the sense of ground), as the holotype was found within the limestones of Germany, whereas -sauros is the Ancient Greek for lizard. Geological range: From the lower Oxfordian (cordatum ammonite zone; NHM 36336 and NHM 36339) to the upper Valanginian (peregrinus ammonite zone; G. lapparenti). Geographical range: European endemic (UK, France, Germany, Italy, and Switzerland). Emended diagnosis: see above., Published as part of Young, Mark Thomas & Andrade, Marco Brandalise De, 2009, What is Geosaurus? Redescription of Geosaurus giganteus (Thalattosuchia: Metriorhynchidae) from the Upper Jurassic of Bayern, Germany, pp. 551-585 in Zoological Journal of the Linnean Society 157 (3) on page 578, DOI: 10.1111/j.1096-3642.2009.00536.x, http://zenodo.org/record/5443313

Variation in modern crocodilian and extinct thalattosuchian crocodylomorph skull morphology is only weakly correlated with phylogeny, implying that factors other than evolutionary proximity play important roles in determining crocodile skull shape. To further explore factors potentially influencing morphological differentiation within the Thalattosuchia, we examine teleosaurid and metriorhynchid skull shape variation within a mechanical and dietary context using a combination of finite element modelling and multivariate statistics. Patterns of stress distribution through the skull were found to be very similar in teleosaurid and metriorhynchid species, with stress peaking at the posterior constriction of the snout and around the enlarged supratemporal fenestrae. However, the magnitudes of stresses differ, with metriorhynchids having generally stronger skulls. As with modern crocodilians, a strong linear relationship between skull length and skull strength exists, with short-snouted morphotypes experiencing less stress through the skull than long-snouted morphotypes under equivalent loads. Selection on snout shape related to dietary preference was found to work in orthogonal directions in the two families: diet is associated with snout length in teleosaurids and with snout width in metriorhynchids, suggesting that teleosaurid skulls were adapted for speed of attack and metriorhynchid skulls for force production. Evidence also indicates that morphological and functional differentiation of the skull occurred as a result of dietary preference, allowing closely related sympatric species to exploit a limited environment. Comparisons of the mechanical performance of the thalattosuchian skull with extant crocodilians show that teleosaurids and long-snouted metriorhynchids exhibit stress magnitudes similar to or greater than those of long-snouted modern forms, whereas short-snouted metriorhynchids display stress magnitudes converging on those found in short-snouted modern species. As a result, teleosaurids and long-snouted metriorhynchids were probably restricted to lateral attacks of the head and neck, but short-snouted metriorhynchids may have been able to employ the grasp and shake and/or ‘death roll’ feeding and foraging behaviours.

Se revalida la especie Metriorhynchus -westermanni Gasparini a partir de un nuevo espécimen de cocodrilo marino caloviano (Metriohrynchidae) hallado en el curso medio de quebrada Cherejara, Sierra del Medio, Región de Antofagasta, Chile. El análisis del neurocráneo y de los huesos asociados demuestra que el holotipo de M. westermanni no es unjuvenil deMetriohrynchus casamiquelai Gasparini y Chong, como anteriormente se propuso. Varias diferencias morfológicas tales como frontal y parietal en el mismo plano, ausencia de depresión medial en el sector interorbital del frontal, piso de la fosa supratemporal plano y horizontal, narinas internas con forma de lágrima con la base más ancha caudalmente y separadas por un septo completo, justifican revalidar a M. westermanni. De esta manera aumenta la diversidad de cocodrilos marinos jurásicos en el oeste del Gondwana, con predominio de registros chilenos en el Jurásico Medio.

The presence of salt-excreting glands in extinct marine sauropsids has been long suspected based on skull morphology. Previously, we described for the first time the natural casts of salt-excreting glands in the head of the Jurassic metriorhynchid crocodyliform Geosaurus araucanensis from the Tithonian of the Vaca Muerta Formation in the Neuquen Basin (Argentina). In the present study, salt-excreting glands are identified in three new individuals (adult, a sub-adult and a juvenile) referable to the same species. New material provides significant information on the salt glands form and function and permit integration of evolutionary scenarios proposed on a physiological basis in extant taxa with evidence from the fossil record. G. araucanensis represents an advanced stage of the basic physiological model to marine adaptations in reptiles. G. araucanensis salt glands were hypertrophied. On this basis, it can be hypothesized that these glands had a high excretory capability. This stage implies that G. araucanensis (like extant pelagic reptiles, e.g. cheloniids) could have maintained constant plasma osmolality even when seawater or osmoconforming prey were ingested. A gradual model of marine adaptation in crocodyliforms based on physiology (freshwater to coastal/estuarine to estuarine /marine to pelagic life) is congruent with the phylogeny of crocodyliforms based on skeletal morphology. The fossil record suggests that the stage of marine pelagic adaptation was achieved by the Early Middle Jurassic. Salt gland size in the juvenile suggests that juveniles were, like adults, pelagic.