References of "Fischer, Valentin"
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See detailExtinctions et renouvellements fauniques chez les reptiles marins du Crétacé
Bardet, Nathalie; Fischer, Valentin ULg; Jouve, Stéphane et al

Conference (2011, December)

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See detailPas d’extinction à la limite Jurassique–Crétacé pour les ichthyosaures
Fischer, Valentin ULg; Maisch, Michael; Naish, Darren et al

Conference (2011, December)

Les ichthyosaures sont un groupe diversifié de reptiles marins mésozoïques. Pour de nombreux auteurs, trois extinctions majeures ont perturbé leur longue histoire évolutive : une à la fin du Trias, une à ... [more ▼]

Les ichthyosaures sont un groupe diversifié de reptiles marins mésozoïques. Pour de nombreux auteurs, trois extinctions majeures ont perturbé leur longue histoire évolutive : une à la fin du Trias, une à la limite Jurassique–Crétacé (JCB) et une (résultant en l’extinction totale) à la limite Cénomanien–Turonien. On croyait que l’extinction de la JCB avait éradiqué la plupart des morphotypes particuliers trouvés dans le Jurassique supérieur, à la faveur de quelques formes crétacées considérées moins spécialisées. Ici, nous réévaluons cette hypothèse en utilisant des analyses phylogénétiques et des taux de cladogenèse/survie/extinction. Notre analyse phylogénétique indique que les ophthalmosauridés (clade unissant tous les ichtyosaures post-bajociens) ont divergé très tôt dans leur histoire en deux clades distincts ; tous deux traversent la JCB et persistent au moins jusqu’ à l'Albien terminal. Pour évaluer l'effet de l'extinction de la JCB sur les ichthyosaures, nous avons calculé des taux de cladogenèse, d'extinction, et de survie pour chaque étage de l'intervalle Oxfordien-Barrémien, selon différents scénarii. Le taux d'extinction de la JCB ne surpasse pas le taux « background » pour l'intervalle Oxfordien-Barrémien et la JCB enregistre un des taux de survie le plus élevé de l'intervalle. Par conséquent, il n'existe actuellement aucune preuve que les ichthyosaures aient été touchés par une extinction à la JCB, contrairement à de nombreux autres groupes d’animaux marins. Les ophthalmosauridés restent diversifiés de leur rayonnement rapide au Jurassique moyen jusqu’à leur extinction totale au début du Crétacé supérieur. [less ▲]

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See detailNew ophthalmosaurids from Europe and Russia broaden the biodiversity of Early Cretaceous ichthyosaurs
Fischer, Valentin ULg

Poster (2011, November)

Ophthalmosauridae is a successful clade of ichthyosaurs that rapidly diversified during the Middle Jurassic. By Late Jurassic, Ophthalmosauridae were diverse, widespread, and formed an important component ... [more ▼]

Ophthalmosauridae is a successful clade of ichthyosaurs that rapidly diversified during the Middle Jurassic. By Late Jurassic, Ophthalmosauridae were diverse, widespread, and formed an important component of the marine trophic webs. By contrast, the record of Berriasian- Aptian ichthyosaurs is extremely poor, and all ichthyosaurs from that interval have been referred to a single genus, Platypterygius, until recently. This apparent diversity drop led numerous authors to recognize a severe ichthyosaur extinction at the end of the Jurassic that left ichthyosaurs as a small group on the decline. New specimens from poorly sampled time periods (late Valanginian, late Hauterivian and late Barremian) in Europe and Russia contradict this latest Jurassic extinction hypothesis and show that new and highly derived as well as typically ‘Late Jurassic’ ichthyosaurs roamed the Eurasian archipelago during the Early Cretaceous. Moreover, these new forms occupied ecological niches markedly different from that of Platypterygius, significantly broadening the disparity and ecological diversity of Cretaceous ichthyosaurs [less ▲]

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See detailA new longirostrine ichthyosaur (Reptilia) from the Toarcian of France broadens the ecological diversity of the genus Temnodontosaurus
Martin, Jeremy; Fischer, Valentin ULg; Vincent, Peggy et al

Poster (2011, September)

The ichthyosaur genus Temnodontosaurus has always been viewed as a top predator of the Early Jurassic marine environments, while other contemporaneous ichthyosaurs such as leptonectids and stenopterygiids ... [more ▼]

The ichthyosaur genus Temnodontosaurus has always been viewed as a top predator of the Early Jurassic marine environments, while other contemporaneous ichthyosaurs such as leptonectids and stenopterygiids were occupying the lower trophic levels. We describe here an almost complete skeleton of this successful genus from the middle Toarcian (Lower Jurassic) of the Beaujolais foothills near Lyon, France, and assign it to a new species of Temnodontosaurus. This specimen exhibits cranial peculiarities such as a thin, elongated, and likely edentulous rostrum, as well as a reduced quadrate. Such morphological combination indicates dietary preferences that markedly differ from other species referred to as Temnodontosaurus. Despite a conservative postcranial skeleton, we propose that Temnodontosaurus is one of the most ecologically diverse genera of ichthyosaurs, including apex predators, small and soft prey longirostrine hunters, and generalized forms. Ammonites collected along the described specimen indicate that the new species is younger (bifrons ammonite zone) than most known Toarcian ichthyosaurs and therefore slightly postdates the severe environmental changes and marine invertebrate extinctions that occur during the Toarcian Oceanic Anoxic Event. The present study hence raises the question whether the speciation of Temnodontosaurus towards a new ecological niche, may have been a consequence of the post-crisis marine ecosystem reorganization. [less ▲]

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See detailHigh diversity in late Early Cretaceous ichthyosaurs part II: The Cambridge Greensand material
Fischer, Valentin ULg

Conference (2011, September)

Recent and on-going work on Canadian and French Cretaceous ichthyosaurs has unveiled a high diversity of Albian ophthalmosaurids, suggesting the extinction of ichthyosaurs which occurs during the ... [more ▼]

Recent and on-going work on Canadian and French Cretaceous ichthyosaurs has unveiled a high diversity of Albian ophthalmosaurids, suggesting the extinction of ichthyosaurs which occurs during the Cenomanian was a much more severe event than previously supposed. Yet the ichthyosaur assemblages from other areas such as the USA and Australia are monospecific, suggesting that the diversity of ichthyosaurs was not universally high. The Cambridge Greensand ichthyosaur material, which has not been the subject of any thorough study since 1869, consists of about 900 specimens, the vast majority of which are isolated bones. Nevertheless, this abundant material offers a good opportunity to assess the diversity of the ichthyosaurs that roamed the western England Sea during the late Albian–Early Cenomanian interval. In order to assess this diversity, diagnostic bones such as basioccipitals, stapes, humeri and femora were compared to that of other ophthalmosaurids. Several morphotypes, some represented by 10+ specimens are recognized. Articulated specimens were used to unite cranial and appendicular bone morphotypes to a taxon. An extremely diverse assemblage of at least 5 distinct taxa is recognized in the Cambridge Greensand Formation: Platypterygius sp., two new genera that have representatives in southeastern France and Germany, a Brachypterygius/Aegirosaurus morphotype, and the long-forgotten but diagnostic Cetarthrosaurus walkeri, for which we found a second and better preserved specimen. The diversity of the ‘mid’ Cretaceous ichthyosaurs from Europe now matches that of the Early Jurassic, a period sometimes seen as the ‘Golden Age’ of post-Triassic ichthyosaurs. [less ▲]

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See detailThe Strange Case of the Jurassic Ichthyosaur
Liston, Jeff; Naish, Darren; Fischer, Valentin ULg

Conference (2011, September)

A report is given on the four decades of unpublished research on a novel ichthyosaur taxon from Iraq. Found in 1952 by field workers for Iraq Oil, it was donated to the Natural History Museum (London ... [more ▼]

A report is given on the four decades of unpublished research on a novel ichthyosaur taxon from Iraq. Found in 1952 by field workers for Iraq Oil, it was donated to the Natural History Museum (London), then borrowed by the late Robert M. Appleby at University College, Cardiff. Appleby aimed to complete a full description of the specimen; his final manuscript also included an extensive discussion of the stratigraphic provenance of the specimen, its phylogenetic affinities, and speculations on its possible ecology. During his investigation, a broad collaboration ensued with members of the universities of Reading and Cambridge and HV Dunnington & Associates (exploration and resource appraisal consultants), as Appleby attempted to constrain the precise age of the specimen within the Jurassic Sargelu Formation. However, the manuscript resulting from this collaboration (submitted to the journal Palaeontology in 1979) was not deemed to have satisfactorily addressed that outstanding question. Although Appleby continued to work widely on ichthyosaurs up until his death in 2004, he was unable to resolve this problem. Subsequent work by the first two authors, incorporating archival research and a revisiting of earlier laboratory techniques, has led to a conclusive resolution of this issue, making it possible for a manuscript describing the specimen to finally be acceptable for publication. Resulting from one of several pieces of Appleby’s unpublished research, the new Iraq taxon has major implications for our understanding of ichthyosaurian diversity, phylogeny and distribution across time and space. [less ▲]

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See detailThe Cenomanian marine reorganization
Fischer, Valentin ULg

Poster (2011, January)

The middle Cretaceous is usually associated with numerous climatic and oceanic perturbations, and a minor to intermediate extinction event at the Cenomanian-Turonian (CTB) boundary. Amongst marine ... [more ▼]

The middle Cretaceous is usually associated with numerous climatic and oceanic perturbations, and a minor to intermediate extinction event at the Cenomanian-Turonian (CTB) boundary. Amongst marine vertebrate palaeontologists, the CTB is mostly known as the extinction of the last ichthyosaurs (Reptilia), after a long period of decline (e.g. Bardet, 1992; Bardet, 1994; Sander, 2000; Lingham-Soliar, 2003). However, new data from France, Canada and Russia indicates that the diversity of late Early Cretaceous ichthyosaurs was far higher than previously thought, both in terms of taxonomical and ecological diversity, but the Cenomanian ichthyosaur diversity remains extremely low. This suggests that the ichthyosaur extinction is far more severe than initially thought and took place during the whole duration of the Cenomanian, in a diachronic fashion. Additionally, a compilation of the current data on the diversity of other marine vertebrates groups shows that the Cenomanian is a peculiar stage within the Cretaceous, with the radiation burst of marine squamates, such as dolichosaurs and mosasauroids (Bardet et al., 2007; Bardet et al., 2008), as well as chondrichtyans, polycotylid plesiosaurs and teleost fishes (e.g. Cumbaa et al., 2010; Schultze et al., 2010). This profound reorganisation of the marine ecosystems (coeval with the onset of the “Chalk sea”) was probably driven by external, physical factors given the diversity of biotic responses. The numerous potential causes for that major reorganisation renders the identification of its precise mechanisms difficult. [less ▲]

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See detailThe first definite record of a Valanginian ichthyosaur and its implications on the evolution of post-Liassic Ichthyosauria
Fischer, Valentin ULg; Clément, Arnaud; Guiomar, Myette et al

in Cretaceous Research (2011), 32(2), 155-163

A complete ichthyosaur rostrum, with 124 associated teeth, was recently discovered in Laux-Montaux locality, department of Drôme, southeastern France. The associated belemnites and ammonites indicate a ... [more ▼]

A complete ichthyosaur rostrum, with 124 associated teeth, was recently discovered in Laux-Montaux locality, department of Drôme, southeastern France. The associated belemnites and ammonites indicate a late Valanginian age (Neocomites peregrinus Zone, Olcostephanus nicklesi Subzone) for this fossil, which consequently represents the first diagnostic ichthyosaur ever reported from Valanginian strata. This specimen also represents the first occurrence of Aegirosaurus outside the Tithonian (Upper Jurassic) lithographic limestones of Bavaria (southern Germany). Tooth morphology and wear pattern suggest that Aegirosaurus belonged to the “Pierce II/ Generalist” feeding guild, which was hitherto not represented in post-Liassic ichthyosaurs. Most Late Jurassic ichthyosaurs actually crossed the Jurassic-Cretaceous boundary. [less ▲]

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See detailA new Barremian (Early Cretaceous) ichthyosaur from western Russia
Fischer, Valentin ULg; Masure, Edwige; Arkhangelsky, Maxim et al

in Journal of Vertebrate Paleontology (2011), 31(5), 1010-1025

A new ophthalmosaurid ichthyosaur, Sveltonectes insolitus gen. et sp. nov., is described from a sub-complete and three-dimensionally preserved specimen from the late Barremian of western Russia. This new ... [more ▼]

A new ophthalmosaurid ichthyosaur, Sveltonectes insolitus gen. et sp. nov., is described from a sub-complete and three-dimensionally preserved specimen from the late Barremian of western Russia. This new taxon is supported by 11 cranial, dental, and postcranial autapomorphies, and is also characterized by features previously considered as autapomorphic for some other Ophthalmosauridae, such as a processus narialis on the prefrontal and relatively long hindfins with pre- and postaxial accessory digits. We conducted a new phylogenetic analysis of Thunnosauria, which supports a ‘Stenopterygius-origin’ for Ophthalmosauridae. Sveltonectes is regarded as the sister taxon of Aegirosaurus, which shares a similar skull roof construction. Contrary to most other Cretaceous ichthyosaurs, Sveltonectes is characterized by delicate and sharply pointed teeth, confirming that the Ophthalmosauridae were ecologically highly diversified during the Early Cretaceous [less ▲]

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See detailNew data on the palaeobiogeography of Early Jurassic marine reptiles: the Toarcian ichthyosaur fauna of the Vocontian Basin (SE France)
Fischer, Valentin ULg; Guiomar, Myette; Godefroit, Pascal

in Neues Jahrbuch für Geologie und Palaontologie. Abhandlungen (2011), 261(1), 111-127

The Vocontian Basin (SE France) was formed along the northwestern border of Tethys during Mesozoic times. Mainly known for its rich ammonite fauna, this basin has also yielded several Lower Jurassic ... [more ▼]

The Vocontian Basin (SE France) was formed along the northwestern border of Tethys during Mesozoic times. Mainly known for its rich ammonite fauna, this basin has also yielded several Lower Jurassic ichthyosaurs. The specimens discussed here were discovered in lower Toarcian limestone and marl successions in the vicinity of Digne-les-Bains, High-Provence Alps. The best-preserved specimen is identified as Suevoleviathan sp., a rare taxon previously reported only in southern Germany. Along with this specimen, premaxillae and paddle elements of Eurhinosaurus sp. and probable Stenopterygiidae centra were found in neighbouring localities. These specimens were preserved thanks to the deposition of soft anoxic marls or calcarodetritic sediments, coeval with other anoxic shales in Europe (the Toarcian Oceanic Anoxic Event or T-OAE), which allows faunal comparisons between these basins. The localities from the Vocontian Basin are closer to the Tethys than any other sites where identifiable Toarcian ichthyosaurs have been found in Europe. Nevertheless, the Vocontian ichthyosaur assemblage is strikingly similar to those in other basins across Europe. It suggests that Toarcian ichthyosaurs had a wide palaeobiogeographical distribution, reflecting their anatomical adaptations as highly mobile swimmers. [less ▲]

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See detailReconsidering the extinction of ichthyosaurs
Fischer, Valentin ULg

Conference (2010, October)

Despite their extreme adaptation to life in open sea, ichthyosaurs were one of the first major groups of post-Triassic marine reptiles to disappear, at the end of Cenomanian, whereas plesiosaurs ... [more ▼]

Despite their extreme adaptation to life in open sea, ichthyosaurs were one of the first major groups of post-Triassic marine reptiles to disappear, at the end of Cenomanian, whereas plesiosaurs, mosasaurs and numerous families of marine crocodiles and sea turtles disappeared during the Cretaceous/Paleocene Extinction Event. It has been proposed that unique biological factors drove ichthyosaurs to extinction, namely a break in the food chain at the level of belemnites or a progressive ecological replacement by teleost fishes since the Middle Jurassic. However, new discoveries in France and Russia turn both these hypotheses unsatisfactory because ichthyosaur diversity remained high during the Early Cretaceous both from taxonomic and ecological points of view, with the persistence of several Late Jurassic genera into the Early Cretaceous and the colonization of various feeding guilds. The extinction of ichthyosaurs during the Cenomanian was therefore more sudden than previously described. The present study aims at replacing the extinction of ichthyosaurs within the global context of changes in marine ecosystems during the ‘middle’ Cretaceous. The ‘middle’ Cretaceous (Aptian-Turonian) is indeed punctuated by numerous and profound global climatic and oceanic changes, as well as intense underwater volcanism. These factors led to recurrent anoxic events, sometimes of worldwide extension. Interestingly, the peak of changes in the geosphere, taking place during the Cenomanian, coincides with major biological changes within the marine realm: the rise of polycotylid plesiosaurs, marine squamates, teleost fishes and chondrichtyans, the onset of the “Chalk sea”, and an extinction within marine invertebrates communities. Ichthyosaurs disappeared during this profound reorganization of the marine ecosystems. However, the precise mechanisms that lead to the sudden extinction of these successful marine reptiles cannot be understood in the current state of our knowledge given the multitude of possible causes occurring at the same time. [less ▲]

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See detailAn Early Cretaceous ichthyosaur from SE France: implications on the evolution of post-Liassic Ichthyosauria
Fischer, Valentin ULg; Clément, Arnaud; Guiomar, Myette et al

Conference (2010, June)

A complete ichthyosaur rostrum with 124 associated teeth was recently discovered in Laux-Montaux locality, department of Drôme, southeastern France. The associated belemnites and ammonites indicate a late ... [more ▼]

A complete ichthyosaur rostrum with 124 associated teeth was recently discovered in Laux-Montaux locality, department of Drôme, southeastern France. The associated belemnites and ammonites indicate a late Valanginian age (Neocomites peregrinus Zone, Olcostephanus nicklesi Subzone) for this fossil, which consequently represents the first diagnostic ichthyosaur ever reported from Valanginian strata. Despite its incompleteness, this specimen is perfectly consistent with Aegirosaurus leptospondylus WAGNER 1853 and is therefore referred to this rare taxon. This specimen thus greatly increases the temporal and geographic biozones of this taxon, which was previously restricted to the Tithonian (Upper Jurassic) lithographic limestones of Bavaria (southern Germany). Moreover, it indicates that Late Jurassic ichthyosaurs actually crossed the Jurassic-Cretaceous boundary with a much lighter diversity drop than previously supposed. Finally, tooth morphology and wear pattern suggest that Aegirosaurus belonged to the “Pierce II/ Generalist” feeding guild sensu Massare (1987; 1997), which was hitherto not represented in post-Liassic ichthyosaurs. [less ▲]

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See detailHigh diversity in late Early Cretaceous ichthyosaurs
Fischer, Valentin ULg; Guiomar, Myette; Godefroit, Pascal

Poster (2009, October)

Considered as the last survivors of a dying group, all Cretaceous ichthyosaurs have traditionally been incorporated within a single genus, Platypterygius. This waste-basket genus includes large ... [more ▼]

Considered as the last survivors of a dying group, all Cretaceous ichthyosaurs have traditionally been incorporated within a single genus, Platypterygius. This waste-basket genus includes large ichthyosaurs with numerous, large and conical tooth crowns and bulbous polygonal root well anchored in dental grooves. With such a dentition, Platypterygius can be included within the “Smash guild”. However, the study of new specimens from the Aptian-Albian marls of the Vocontian basin (SE France) reveals an unexpected diversity of late Early Cretaceous ichthyosaurs. Beside “classical” Platypterygius specimens, another type of ichthyosaur with very tiny and pointed teeth has been found in the mid-Albian marls of Sisteron, in High-Provence Alps. This new taxon is based on a partial crushed skull, two basioccipitals, 8 teeth, and 15 centra. The teeth range from 20mm to 2cm and are highly compressed labio-lingualy, with a thickness/wideness ratio of the root sometimes as low as 1/4. Crowns are slightly curved and sharply pointed, indicating a diet of small and soft preys. Interestingly, although the rostral bones are slender and delicate – thus radically different from conventional Late Early Cretaceous ichthyosaurs – the basioccipital of this taxon shares many characters with Platypterygius and is of the same overall size. Together with the recently named genus Maiaspondylus from the Albian of western Canada, these specimens suggest a higher diversity of late Early Cretaceous ichthyosaurs, in contradiction with the current view of ichthyosaur extinction, said to be gradually decreasing in diversity since the Middle Jurassic. In fact, the number of ecological niches occupied by ichthyosaurs apparently even increased from the Late Jurassic until the late Early Cretaceous. Therefore, the ecological impact of the Cenomanian-Turonian boundary on marine reptile faunas was probably more severe than previously thought. [less ▲]

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See detailLes ichthyosaures du sud-­est de la France
Fischer, Valentin ULg

Master's dissertation (2009)

The examination of the ichthyosaur collections housed at the “Réserve géologique de Haute-Provence” (RGHP, High-Provence Alps, South-East France) brings new data on the ecology and diversity of Jurassic ... [more ▼]

The examination of the ichthyosaur collections housed at the “Réserve géologique de Haute-Provence” (RGHP, High-Provence Alps, South-East France) brings new data on the ecology and diversity of Jurassic and Cretaceous ichthyosaurs. The specimens of this collection all come from the Vocontian Trough, a deep Mesozoic basin lying at the North-western border of Tethys, making this area the southernmost European locality where diagnostic ichthyosaurs have been found. However, faunal assemblages found in the Vocontian Basin are identical to other European assemblages, especially during Toarcian (Lower Jurassic). Of particular interest is the presence of the Toarcian genus Suevoleviathan, recorded for the first time outside of the German basins. Every Toarcian ichthyosaur genus is now found in at least two European basins, seriously questioning Toarcian ichthyosaur endemism, at least at the genus level. This specimen has been found along with Eurhinosaurus longirostris and several Thunnosauria indet. aff. Stenopterygius. It is shown that the Toarcian ichthyosaur “endemism” is most probably an effect of preservational biases. Aside from their geographic remoteness compared to the typical ichthyosaur localities, the stratigraphic position of the RGHP specimens is also particularly interesting, especially during the Cretaceous: the first diagnostic ichthyosaur clearly belonging to Valanginian strata is described here. This specimen turned out to be assignable to Aegirosaurus leptospondylus, a species previously known only from the Tithonian lithographic limestones of Bavaria (Bardet & Fernández, 2000). Three Albian specimens are also described. One of them is referable to the cosmopolitan genus Platypterygius, while the two others belong to a new taxon, with tiny pointed teeth. This suggests that new taxon marks the colonization of a new ecological niche during the Albian. This has two major implications: firstly the Vocontian basin can now be regarded as one of the best Cretaceous ichthyosaur-bearing localities of the world in terms of ecologic diversity. Secondly, the effect of the Jurassic-Cretaceous boundary extinction (JCB) on post-liassic ichthyosaurs is weak: their diversity remains nearly constant during JCB and up to the Albian. On the contrary the Cenomanian-Turonian boundary extinction seemed to be far more severe than the simple “knock on the head” of a group on the decline since the Middle Jurassic, as seen in the literature. [less ▲]

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See detailNew data on the palaeobiogeography of Toarcian (Lower Jurassic) ichthyosaurs
Fischer, Valentin ULg; Guiomar, Myette; Godefroit, Pascal

Conference (2009, February)

The Vocontian Basin of SE France was formed along the northwestern border of Tethys during Mesozoic times. Mainly known for its rich ammonite fauna, this basin has also yielded Jurassic and Cretaceous ... [more ▼]

The Vocontian Basin of SE France was formed along the northwestern border of Tethys during Mesozoic times. Mainly known for its rich ammonite fauna, this basin has also yielded Jurassic and Cretaceous ichthyosaur fossils. The specimens discussed here were discovered in lower Toarcian limestone and marl successions in the vicinity of Digne-les-Bains, High-Provence Alps. One of best-preserved specimens is identified as Suevoleviathan sp., a relatively rare genus previously reported only in the German basins. The specimen is fairly complete but crushed and embedded in limestone from the Falciferum ammonite zone. Because the skull is too damaged to see bone sutures, assignation to this genus is mostly based on fin and coracoid morphology. Along with this specimen, a premaxilla and paddle elements of Eurhinosaurus longirostris and possible Stenopterygiidae centra were found in nearby black marls of the Exaratum ammonite subzone (Falciferum zone, Lower Toarcian; see Floquet et al., 2003 for a detailed stratigraphy). These soft marls were deposited in anoxic waters and are coeval with the Posidonia shales of southwest Germany, the Jet rock formation of northeast England and Grandcourt shales of Luxembourg, which allows faunal comparisons between these basins. The localities from the Vocontian Basin are closer to the Tethys than other sites where Toarcian identifiable ichthyosaurs have been found in Europe. Nevertheless all identifiable specimens from the Vocontian Basin are also identified in other basins across Europe. It suggests that Toarcian ichthyosaurs had wide palaeogeographical distributions and were highly mobile swimmers, perfectly adapted to open marine environments. [less ▲]

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