References of "Fischer, Valentin"
     in
Bookmark and Share    
Full Text
See detailCampanian-Maastrichtian fossils from southern Belgium and neighbouring countries curated at the University of Liège
Mottequin, Bernard ULg; Denayer, Julien ULg; Fischer, Valentin ULg et al

in Jagt, John W. M.; Jagt-Yazykova, Ellena (Eds.) The Maastrichtian Stage; the current concept. Workshop programme, abstracts and field guide (2012, September 06)

Detailed reference viewed: 73 (10 ULg)
See detailMesozoic marine reptile palaeobiogeography in response to drifting plates
Bardet, Nathalie; Fischer, Valentin ULg; Houssaye, Alexandra et al

Conference (2012, September)

Mesosaurus Broom, 1913, from the Early Permian, is the first aquatic reptile known in the fossil record. Its co-occurrence in both South Africa (South Africa) and South America (Brazil, Uruguay) made it ... [more ▼]

Mesosaurus Broom, 1913, from the Early Permian, is the first aquatic reptile known in the fossil record. Its co-occurrence in both South Africa (South Africa) and South America (Brazil, Uruguay) made it one of the key-fossils - with the pteridospermatophyta plant Glossopteris - used by the German meteorologist / geophysician Alfred Wegener to support his theory of the Continental Drift (Kontinentalverschiebung), first published in 1912. But Mesosaurus was only the “tip of the iceberg” as, during the Mesozoic, various clades of reptiles massively invaded the aquatic, and more especially, the marine realm. They were highly diversified both systematically and ecologically, and some of them were large top-predators of the marine ecosystems. The main groups were, in order of appearance in the fossil record, Ichthyosauria (earliest Triassic – early Late Cretaceous), Sauropterygia (nothosaurs, pachypleurosaurs, placodonts, plesiosaurs; Early Triassic – latest Cretaceous), Thalattosauria (Middle-Late Triassic), Pleurosauria (Early Jurassic–Early Cretaceous), as well as, among others, several lineages of Chelonians (e.g. chelonioids, bothremydids, “thalassemyds”), Crocodyliformes (thalattosuchians, dyrosaurids, pholidosaurids, gavialoids) and Squamates (mosasauroids, “dolichosaurs”, marine snakes). During the Mesozoic, the palaeobiogeographical distributions and the dispersion events of these marine reptiles closely followed the break-off of the Pangea induced by plate tectonic movements. Although marine reptiles can help in determining the possible date of opening of marine corridors, the information they provide are less precise than that delivered by terrestrial faunas, as the marine realm is a more open system and various migration ways are always possible. Generally, the Triassic taxa were animals with a restricted palaeobiogeographical distribution living near the coastlines of the Pangea. From the end of the Triassic and during the Jurassic, the break-off of the Pangea resulted in the formation of large marine corridors, allowing open-sea marine reptiles such as ichthyosaurs, plesiosaurs and crocodyliformes to spread out over large distances. As an example, similar marine reptile faunas are known from the Jurassic of Europe and southern South America, as a result of dispersion events via the Hispanic Corridor that connected the Tethys / North Atlantic and Pacific realms at this time. During the Cretaceous, and notably with the expansion of the Atlantic Ocean, most of these reptiles were cosmopolite and open-sea forms (plesiosaurs, mosasaurid squamates, chelonioid turtles). However, even if large faunal interchanges were possible, some provinces such as the Northern and Southern margins of the Tethys were characterized by a peculiar faunal identity, notably concerning mosasaurids, despite the apparent absence of barriers. So, if Continental Drift enabled circulation and faunal interchanges, other parameters such as ecological constraints probably also played a role in the distribution of these marine reptile faunas. [less ▲]

Detailed reference viewed: 134 (1 ULg)
See detailA severe drop in Eurasian ichthyosaur diversity prior to their late Cenomanian extinction: local or global signal?
Fischer, Valentin ULg

Conference (2012, September)

During the last decade, our knowledge of the taxonomic diversity of the Early Cretaceous ichthyosaurs (Mesozoic marine reptiles) has increased significantly, with the recognition of new species, genera ... [more ▼]

During the last decade, our knowledge of the taxonomic diversity of the Early Cretaceous ichthyosaurs (Mesozoic marine reptiles) has increased significantly, with the recognition of new species, genera, and subfamilies from Canada, Europe, and Russia. New data from England, France, and western Russia suggest ichthyosaurs remained diverse and abundant in western Eurasian marine ecosystems up to the late Albian–early Cenomanian, with the co-occurrence of three to four taxa occupying two to three distinct ecological niches in each formation considered (Cambridge Greensand Member, England; Marnes Bleues Formation, France; Stoïlensky quarry, Russia). However, the overlying formations (middle–late Cenomanian), consisting of chalk or glauconiferous sands, have yielded a very depauperate ichthyosaur fauna. These ichthyosaur assemblages are monospecific and comprise medium to large-sized, presumably opportunistic predators belonging the genus Platypterygius. This suggests a severe drop in ichthyosaur diversity some 5 millions years before their final extinction, which presumably occurred at or near the Cenomanian–Turonian boundary. However, it is difficult to know if this pattern is biased or genuine: the diversity drop may very well be an effect of preservational/ecological biases as well as a genuine extinction linked to the profound environmental changes occurring during the Cenomanian. The presence of similar impoverished assemblages in Cenomanian sediments worldwide favours the latter hypothesis, but the question remains open for now. [less ▲]

Detailed reference viewed: 50 (4 ULg)
Full Text
Peer Reviewed
See detailNew Ophthalmosaurid Ichthyosaurs from the European Lower Cretaceous Demonstrate Extensive Ichthyosaur Survival across the Jurassic–Cretaceous Boundary
Fischer, Valentin ULg; Maisch, Michael; Naish, Darren et al

in PLoS ONE (2012), 7(1), 29234

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events ... [more ▼]

Background Ichthyosauria is a diverse clade of marine amniotes that spanned most of the Mesozoic. Until recently, most authors interpreted the fossil record as showing that three major extinction events affected this group during its history: one during the latest Triassic, one at the Jurassic–Cretaceous boundary (JCB), and one (resulting in total extinction) at the Cenomanian-Turonian boundary. The JCB was believed to eradicate most of the peculiar morphotypes found in the Late Jurassic, in favor of apparently less specialized forms in the Cretaceous. However, the record of ichthyosaurs from the Berriasian–Barremian interval is extremely limited, and the effects of the end-Jurassic extinction event on ichthyosaurs remains poorly understood. Methodology/Principal Findings Based on new material from the Hauterivian of England and Germany and on abundant material from the Cambridge Greensand Formation, we name a new ophthalmosaurid, Acamptonectes densus gen. et sp. nov. This taxon shares numerous features with Ophthalmosaurus, a genus now restricted to the Callovian–Berriasian interval. Our phylogenetic analysis indicates that Ophthalmosauridae diverged early in its history into two markedly distinct clades, Ophthalmosaurinae and Platypterygiinae, both of which cross the JCB and persist to the late Albian at least. To evaluate the effect of the JCB extinction event on ichthyosaurs, we calculated cladogenesis, extinction, and survival rates for each stage of the Oxfordian–Barremian interval, under different scenarios. The extinction rate during the JCB never surpasses the background extinction rate for the Oxfordian–Barremian interval and the JCB records one of the highest survival rates of the interval. Conclusions/Significance There is currently no evidence that ichthyosaurs were affected by the JCB extinction event, in contrast to many other marine groups. Ophthalmosaurid ichthyosaurs remained diverse from their rapid radiation in the Middle Jurassic to their total extinction at the beginning of the Late Cretaceous. [less ▲]

Detailed reference viewed: 71 (9 ULg)
Full Text
See detailA marine vertebrate fauna from the Toarcian-Aalenian succession of southern Beaujolais, Rhône, France
Suan, Guillaume; Vincent, Peggy; Martin, Jeremy et al

Conference (2012)

Detailed reference viewed: 19 (1 ULg)
Full Text
Peer Reviewed
See detailA longirostrine Temnodontosaurus (Ichthyosauria) with comments on Early Jurassic ichthyosaur niche partitioning and disparity
Martin, Jeremy; Fischer, Valentin ULg; Vincent, Peggy et al

in Palaeontology (2012), 55(1), 9951005

We describe an almost complete ichthyosaur skeleton from the middle Toarcian (Lower Jurassic) of the Beaujolais foothills near Lyon, France, and assign it to Temnodontosaurus azerguensis sp. nov. This new ... [more ▼]

We describe an almost complete ichthyosaur skeleton from the middle Toarcian (Lower Jurassic) of the Beaujolais foothills near Lyon, France, and assign it to Temnodontosaurus azerguensis sp. nov. This new species exhibits cranial peculiarities such as a thin, elongated and possibly edentulous rostrum, as well as a reduced quadrate. These characters indicate dietary preferences that markedly differ from other species referred to Temnodontosaurus, a genus previously considered as the top predator of the Early Jurassic seas. Despite a conservative postcranial skeleton, we propose that Temnodontosaurus is one of the most ecologically disparate genera of ichthyosaurs, including apex predators and now a soft prey longirostrine hunter. Ammonites collected from the same stratigraphic level as the described specimen indicate that the new species is somewhat younger (bifrons ammonite zone) than the most known Toarcian ichthyosaurs and therefore slightly postdates the interval of severe environmental changes and marine invertebrate extinctions known as the Toarcian Oceanic Anoxic Event. The present study therefore raises the question of whether postcrisis recovery of vertebrate faunas, including the radiation of Temnodontosaurus into a new ecological niche, may have been a consequence of marine ecosystem reorganization across this event. [less ▲]

Detailed reference viewed: 29 (4 ULg)
Full Text
Peer Reviewed
See detailNew data on the ichthyosaur Platypterygius hercynicus and its implications for the validity of the genus
Fischer, Valentin ULg

in Acta Palaeontologica Polonica (2012), 57(1), 123134

The description of a nearly complete skull from the late Albian of northwestern France reveals previously unknown anatomical features of Platypterygius hercynicus (Kuhn 1946), and of European Cretaceous ... [more ▼]

The description of a nearly complete skull from the late Albian of northwestern France reveals previously unknown anatomical features of Platypterygius hercynicus (Kuhn 1946), and of European Cretaceous ichthyosaurs in general. These include a wide frontal forming the anteromedial border of the supratemporal fenestra, a parietal excluded from the parietal foramen, and the likely presence of a squamosal, inferred from a very large and deep facet on the quadratojugal. The absence of a squamosal has been considered as an autapomorphy of the genus Platypterygius for more than ten years and has been applied to all known species by default, but the described specimen casts doubt on this putative autapomorphy. Actually, it is shown that all characters that have been proposed previously as autapomorphic for the genus Platypterygius are either not found in all the species currently referred to this genus, or are also present in other Ophthalmosauridae. Consequently, the genus Platypterygius must be completely revised. [less ▲]

Detailed reference viewed: 78 (7 ULg)
See detailExtinctions et renouvellements fauniques chez les reptiles marins du Crétacé
Bardet, Nathalie; Fischer, Valentin ULg; Jouve, Stéphane et al

Conference (2011, December)

Detailed reference viewed: 8 (0 ULg)
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 ▲]

Detailed reference viewed: 70 (5 ULg)
Peer Reviewed
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 ▲]

Detailed reference viewed: 41 (3 ULg)
Peer Reviewed
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 ▲]

Detailed reference viewed: 113 (2 ULg)
Peer Reviewed
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 ▲]

Detailed reference viewed: 77 (3 ULg)
Peer Reviewed
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 ▲]

Detailed reference viewed: 94 (2 ULg)
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 ▲]

Detailed reference viewed: 100 (5 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 73 (7 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 48 (9 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 60 (2 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 149 (3 ULg)
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 ▲]

Detailed reference viewed: 138 (4 ULg)
Peer Reviewed
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 ▲]

Detailed reference viewed: 259 (5 ULg)