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See detailA mysterious giant ichthyosaur from the lowermost Jurassic of Wales
Martin, Jeremy E; Vincent, Peggy; Suan, Guillaume et al

in Acta Palaeontologica Polonica (in press)

Ichthyosaurs rapidly diversified and colonised a wide range of ecological niches during the Early and Middle Triassic period, but experienced a major decline in diversity near the end of the Triassic ... [more ▼]

Ichthyosaurs rapidly diversified and colonised a wide range of ecological niches during the Early and Middle Triassic period, but experienced a major decline in diversity near the end of the Triassic. Timing and causes of this demise and the subsequent rapid radiation of the diverse, but less disparate, parvipelvian ichthyosaurs are still unknown, notably because of inadequate sampling in strata of latest Triassic age. Here, we describe an exceptionally large radius from Lower Jurassic deposits at Penarth near Cardiff, South Wales (UK) the morphology of which places it within the giant Triassic shastasaurids. A tentative total body size estimate, based on a regression analysis of various complete ichthyosaur skeletons, yields a value of 12-15 m. The specimen is substantially younger than any previously reported last known occurrences of shastasaurids and implies a Lazarus range in the lowermost Jurassic for this ichthyosaur morphotype. [less ▲]

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See detailMesozoic marine crises and ichthyosaur history: a non-direct relationship
Fischer, Valentin ULg

Conference (2014, October)

Marine ecosystems underwent several profound crises throughout the Mesozoic; many of them are correlated with supra-regional to worldwide anoxic events. The impact of these crises is relatively well ... [more ▼]

Marine ecosystems underwent several profound crises throughout the Mesozoic; many of them are correlated with supra-regional to worldwide anoxic events. The impact of these crises is relatively well understood among animals occupying lower trophic levels but their influence on top predators of that time, fishes and marine reptiles, remains unclear. The fossil record of marine reptiles is of fluctuating quality but thoroughly revised taxonomic and phylogenetic frameworks now allow assessment of the influence of past climatic and oceanic changes on these top predators, by quantifying their cladogenesis and extinction rates across selected intervals. Here, I focus on ichthyosaurs, a successful clade of marine reptiles that colonized marine ecosystems during most of the Mesozoic. The ichthyosaur record indicates relatively few severe turnovers and a non direct relationship with environmental drivers, notably anoxic events. New fossils from France reveal the middle-late Norian extinctions did not eradicate the clade of whale-sized shastasaurid ichthyosaurs; similarly, the severe early Toarcian anoxic event, the end-Jurassic climate changes and several Cretaceous anoxic events did not impacted ichthyosaurs significantly, at least at the suprageneric level. On the other hand, severe turnovers or extinctions occurred during the latest Triassic and the Cenomanian and are coincident with a number of profound environmental and biotic changes. This indicates that unique drivers fail to explain the turnover patterns in ichthyosaur evolutionary history. Notably, oceanic anoxic events only impacted ichthyosaurs during the end-Cenomanian and did so during a period of intense climatic and biological upheavals. These major crises in ichthyosaur history are seemingly protracted over several million years and are probably best explained by a conjunction of causes. This is part of a wider project that will incorporate data from other contemporaneous groups to shed a new light on the general turnover patterns among marine top predators of the Mesozoic and the influence of ancient environmental changes in shaping their biodiversity. [less ▲]

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See detailLost and found: Rediscovery of de Ryckholt's collection of Cretaceous Mollusca (Belgium and N. France)
Fischer, Valentin ULg; Denayer, Julien ULg; Mottequin, Bernard ULg

in 4th International Palaeontological Congress, Mendoza, Abstracts volume (2014)

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See detailIchthyosaurs from the French Rhaetian indicate a severe turnover across the Triassic–Jurassic boundary
Fischer, Valentin ULg; Cappetta, Henri; Vincent, Peggy et al

in Naturwissenschaften (Die) (2014)

Mesozoic marine reptiles went through a severe turnover near the end of the Triassic. Notably, an important extinction event affected ichthyosaurs, sweeping a large part of the group. This crisis is ... [more ▼]

Mesozoic marine reptiles went through a severe turnover near the end of the Triassic. Notably, an important extinction event affected ichthyosaurs, sweeping a large part of the group. This crisis is, however, obscured by an extremely poor fossil record and is regarded as protracted over the entire Norian–earliest Jurassic interval, for the lack of a more precise scenario. The iconic whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. Here we evaluate the pattern of this turnover among ichthyosaurs by analysing the faunal record of two Rhaetian localities. One locality is Autun, eastern France; we rediscovered in this material the holotypes or partial ‘type’ series of Rachitrema pellati, Actiosaurus gaudryi, Ichthyosaurus rheticus, Ichthyosaurus carinatus and Plesiosaurus bibractensis; a revised taxonomic scheme is proposed. The second assemblage comes from a new locality: Cuers, southeastern France. Both these assemblages provide several lines of evidence for the presence of shastasaurid-like ichthyosaurs in the Rhaetian of Europe. These occurrences suggest that both the demise of shastasaurids and the sudden radiation of neoichthyosaurians occurred within a short time window; this turnover appears not only more abrupt but also more complex than previously postulated and adds a new facet of the end-Triassic mass extinction [less ▲]

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See detailSimbirskiasaurus and Pervushovisaurus reassessed: implications for the taxonomy and cranial osteology of Cretaceous platypterygiine ichthyosaurs
Fischer, Valentin ULg; Arkhangelsky, Maxim; Stenshin, Ilya et al

in Zoological Journal of the Linnean Society (2014), 171(4), 822841

The ichthyosaur fossil record is interspersed by several hiatuses, notably during the Cretaceous. This hampers our understanding of the evolution and extinction of this group of marine reptiles during the ... [more ▼]

The ichthyosaur fossil record is interspersed by several hiatuses, notably during the Cretaceous. This hampers our understanding of the evolution and extinction of this group of marine reptiles during the last 50 million years of its history. Several Cretaceous ichthyosaur taxa named in the past have subsequently been dismissed and referred to the highly inclusive taxon Platypterygius, a trend that has created the impression of low Cretaceous ichthyosaur diversity. Here, we describe the cranial osteology, reassess the stratigraphic age, and evaluate the taxonomy and phylogenetic relationships of two Cretaceous ichthyosaurs from western Russia: Simbirskiasaurus birjukovi from the early Barremian and Pervushovisaurus bannovkensis from the middle Cenomanian, both formerly regarded as nomina dubia, and allocated to Platypterygius sp. and Platypterygius campylodon, respectively. We show that Simbirskiasaurus birjukovi and Pervushovisaurus bannovkensis are valid platypterygiine ophthalmosaurids, notably characterized by a peculiar narial aperture. The cranial anatomy and phylogenetic relationships of these taxa illuminate the evolution of narial aperture anatomy in Cretaceous ichthyosaurs, clarify the phylogenetic relationships among platypterygiines, and provide further arguments for a thorough revision of Platypterygius. [less ▲]

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See detailMesozoic marine reptile palaeobiogeography in response to drifting plates
Bardet, Nathalie; Falconnet, Jocelyn; Fischer, Valentin ULg et al

in Gondwana Research (2014)

During the Mesozoic, various groups of reptiles underwent a spectacular return to an aquatic life, colonizing most marine environments. They were highly diversified both systematically and ecologically ... [more ▼]

During the Mesozoic, various groups of reptiles underwent a spectacular return to an aquatic life, colonizing most marine environments. They were highly diversified both systematically and ecologically, and most were the largest top-predators of the marine ecosystems of their time. The main groups were Ichthyosauria, Sauropterygia, Thalattosauria, and several lineages of Testudinata, Crocodyliformes, Rhynchocephalia and Squamata. Here we show that the palaeobiogeographical distribution of these marine reptiles closely followed the break-up of the supercontinent Pangaea and that they globally used the main marine corridors created by this break-up to disperse. Most Mesozoic marine reptile clades exhibit a cosmopolitan, or at least pandemic, distribution very early in their evolutionary history. The acquisition of morphological adaptations to a fully aquatic life, combined to special thermophysiological characteristics, are probably responsible for these animals to become efficient long-distance open-marine cruisers. Generally, Early Triassic taxa were near-shore animals mainly linked to the Tethys or Panthalassa coastlines. By the end of the Triassic and during the Jurassic, the break-up of Pangaea resulted in the formation of large marine corridors connecting the Tethys to the North Atlantic and Pacific realms, a trend increasing on during the Cretaceous with the expansion of the Atlantic Ocean and the break-up of the southern Gondwana, allowing open-sea marine reptiles to spread out over large distances. However, if large faunal interchanges were possible at a global scale following a dispersal model, some provinces, such as the Mediterranean Tethys, were characterized by a peculiar faunal identity, illustrating an absence of migration with time despite the apparent lack of barriers. So, if Continental Drift enabled global circulations and faunal interchanges via dispersals among Mesozoic marine reptiles, others parameters, such as ecological and biological constraints, probably also played a role in the local endemic distribution of some of these marine groups, as they do today. [less ▲]

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See detailA New Look at Ichthyosaur Long Bone Microanatomy and Histology: Implications for Their Adaptation to an Aquatic Life
Houssaye, Alexandra; Scheyer, Torsten; Kolb, Christian et al

in PLoS ONE (2014), 9(4), 95637

Background Ichthyosaurs are Mesozoic reptiles considered as active swimmers highly adapted to a fully open-marine life. They display a wide range of morphologies illustrating diverse ecological grades ... [more ▼]

Background Ichthyosaurs are Mesozoic reptiles considered as active swimmers highly adapted to a fully open-marine life. They display a wide range of morphologies illustrating diverse ecological grades. Data concerning their bone microanatomical and histological features are rather limited and suggest that ichthyosaurs display a spongious, “osteoporotic-like” bone inner structure, like extant cetaceans. However, some taxa exhibit peculiar features, suggesting that the analysis of the microanatomical and histological characteristics of various ichthyosaur long bones should match the anatomical diversity and provide information about their diverse locomotor abilities and physiology. Methodology/Principal Findings The material analyzed for this study essentially consists of mid-diaphyseal transverse sections from stylopod bones of various ichthyosaurs and of a few microtomographic (both conventional and synchrotron) data. The present contribution discusses the histological and microanatomical variation observed within ichthyosaurs and the peculiarities of some taxa (Mixosaurus, Pessopteryx). Four microanatomical types are described. If Mixosaurus sections differ from those of the other taxa analyzed, the other microanatomical types, characterized by the relative proportion of compact and loose spongiosa of periosteal and endochondral origin respectively, seem to rather especially illustrate variation along the diaphysis in taxa with similar microanatomical features. Our analysis also reveals that primary bone in all the ichthyosaur taxa sampled (to the possible exception of Mixosaurus) is spongy in origin, that cyclical growth is a common pattern among ichthyosaurs, and confirms the previous assumptions of high growth rates in ichthyosaurs. Conclusions/Significance The occurrence of two types of remodelling patterns along the diaphysis, characterized by bone mass decrease and increase respectively is described for the first time. It raises questions about the definition of the osseous microanatomical specializations bone mass increase and osteoporosis, notably based on the processes involved, and reveals the difficulty in determining the true occurrence of these osseous specializations in ichthyosaurs. [less ▲]

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See detailMary Anning’s legacy to French vertebrate palaeontology
Vincent, Peggy; Taquet, Philippe; Fischer, Valentin ULg et al

in Geological Magazine (2014), 151(1), 7-20

The real nature of marine reptile fossils found in England in between the 1700s to the beginning of the 1900s remained enigmatic, until Mary Anning's incredible fossil discoveries and their subsequent ... [more ▼]

The real nature of marine reptile fossils found in England in between the 1700s to the beginning of the 1900s remained enigmatic, until Mary Anning's incredible fossil discoveries and their subsequent study by eminent English and French scientists. In 1820, Georges Cuvier acquired several ichthyosaur specimens found by Mary Anning, now kept or displayed in the Palaeontology Gallery of the MNHN in Paris. Four years later, Cuvier obtained a plesiosaur specimen from Mary Anning, only the second ever discovered. Cuvier was fascinated by these fossils and their study allowed him to apply his comparative anatomical method and to support his catastrophist theory. We re-examined these important specimens from an historical point of view and herein describe them taxonomically for the first time since Cuvier’s works. The Paris specimens belong to two different ichthyosaur genera (Ichthyosaurus and Leptonectes) and one plesiosaur genus (Plesiosaurus). [less ▲]

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See detailA new Lower Cretaceous ichthyosaur from Russia reveals skull shape conservatism within Ophthalmosaurinae
Fischer, Valentin ULg; Arkhangelsky, Maxim; Uspensky, Gleb et al

in Geological Magazine (2014), 151(1), 60-70

Ophthalmosaurinae is a recently recognized clade of derived ichthyosaurs (marine reptiles) ranging from the Bajocian (Middle Jurassic) to the late Albian (late Early Cretaceous). Whereas the Middle-Late ... [more ▼]

Ophthalmosaurinae is a recently recognized clade of derived ichthyosaurs (marine reptiles) ranging from the Bajocian (Middle Jurassic) to the late Albian (late Early Cretaceous). Whereas the Middle-Late Jurassic ophthalmosaurine Ophthalmosaurus is often regarded as a hyperspecialized deep diver, very little is known about the anatomy, evolutionary history, and ecology of Cretaceous ophthalmosaurines because of the scarcity of the fossils and the lack of well-preserved skull material. Here, we describe the skull of a new basal ophthalmosaurine ichthyosaur, Leninia stellans gen. et sp. nov., from the lower Aptian of western Russia, and compare the ocular characteristics of ophthalmosaurids. Leninia is recovered as a basal ophthalmosaurine; it possesses unique traits such as star-shaped frontal–parietal sutures as well as features previously thought to be unique to Ophthalmosaurus such as a supratemporal–stapes contact. A large sclerotic aperture – significantly bigger than in platypterygiine ophthalmosaurids and similar to that of the largest-eyed modern animals (giant and colossal squids) – and reduced dentition appear widespread within ophthalmosaurines. This conservatism suggests ophthalmosaurine ophthalmosaurids occupied similar ecological niche(s) throughout their long evolutionary history. [less ▲]

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See detailHigh Diversity in Cretaceous Ichthyosaurs from Europe Prior to Their Extinction
Fischer, Valentin ULg; Bardet, Nathalie; Guiomar, Myette et al

in PLoS ONE (2014), 9(1), 84709

Background: Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group ... [more ▼]

Background: Ichthyosaurs are reptiles that inhabited the marine realm during most of the Mesozoic. Their Cretaceous representatives have traditionally been considered as the last survivors of a group declining since the Jurassic. Recently, however, an unexpected diversity has been described in Upper Jurassic–Lower Cretaceous deposits, but is widely spread across time and space, giving small clues on the adaptive potential and ecosystem control of the last ichthyosaurs. The famous but little studied English Gault Formation and ‘greensands’ deposits (the Upper Greensand Formation and the Cambridge Greensand Member of the Lower Chalk Formation) offer an unprecedented opportunity to investigate this topic, containing thousands of ichthyosaur remains spanning the Early–Late Cretaceous boundary. Methodology/Principal findings: To assess the diversity of the ichthyosaur assemblage from these sedimentary bodies, we recognized morphotypes within each type of bones. We grouped these morphotypes together, when possible, by using articulated specimens from the same formations and from new localities in the Vocontian Basin (France); a revised taxonomic scheme is proposed. We recognize the following taxa in the ‘greensands’: the platypterygiines ‘Platypterygius’ sp. and Sisteronia seeleyi gen. et sp. nov., indeterminate ophthalmosaurines and the rare incertae sedis Cetarthrosaurus walkeri. The taxonomic diversity of late Albian ichthyosaurs now matches that of older, well-known intervals such as the Toarcian or the Tithonian. Contrasting tooth shapes and wear patterns suggest that these ichthyosaurs colonized three distinct feeding guilds, despite the presence of numerous plesiosaur taxa. Conclusion/Significance: Western Europe was a diversity hot-spot for ichthyosaurs a few million years prior to their final extinction. By contrast, the low diversity in Australia and U.S.A. suggests strong geographical disparities in the diversity pattern of Albian–early Cenomanian ichthyosaurs. This provides a whole new context to investigate the extinction of these successful marine reptiles, at the end of the Cenomanian. [less ▲]

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See detailRediscovery of the forgotten de Ryckholt Collection (gastropods, bivalves, worms; Late Cretaceous, Belgium)
Denayer, Julien ULg; Fischer, Valentin ULg; Mottequin, Bernard ULg

in Cretaceous Research (2014), 47

A significant part of the collection of mid- and Late Cretaceous (Cenomanian, Campanian and Maastrichtian) gastropods, bivalves and worms described and/or illustrated by de Ryckholt in his seminal work ... [more ▼]

A significant part of the collection of mid- and Late Cretaceous (Cenomanian, Campanian and Maastrichtian) gastropods, bivalves and worms described and/or illustrated by de Ryckholt in his seminal work Mélanges paléontologiques between 1854 and 1862, has recently been retraced in the historical collections at Liège University. Of the original collection, more than 206 specimens, including 196 nominal types (lectotypes and genotypes), all considered lost, are now available. The genotypes of the gastropod genera Tudicula de Ryckholt, 1862a and Prosopostoma de Ryckholt, 1862a are photographically illustrated for the first time. Prosopostoma bucculans, from the Cenomanian Bernissart Formation (formerly ‘Tourtia de Tournai’), is here chosen as the type species of the genus Prosopostoma, a possible stromboid. We also reassess the stratigraphic age of the type localities under the revised stratigraphic framework of Belgium and a detailed account on the research history of this material, in order to provide a thorough scientific background for future study of this formidable collection. [less ▲]

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See detailA basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs
Naish, Darren; Fischer, Valentin ULg; Liston, Jeff et al

Poster (2013, October)

A new thunnosaurian from the Kurdistan region of Iraq represents the first post-Triassic ichthyosaur from the Middle East. The specimen is an articulated partial skeleton that includes a partial skull ... [more ▼]

A new thunnosaurian from the Kurdistan region of Iraq represents the first post-Triassic ichthyosaur from the Middle East. The specimen is an articulated partial skeleton that includes a partial skull, complete left forefin, partial ribcage and anterior section of the vertebral column. Associated palynomorphs uncontroversially date the specimen (preserved on a loose slab of matrix) to the late Hauterivian- Barremian interval of the Early Cretaceous. A posterior projection on the humerus, short and trapezoidal humerus, enlarged intermedium, and trapezoidal cervical and anterior dorsal neural spines represent autapomorphies. Forefin morphology is archaic: the carpals, metacarpals and phalanges form a mosaic similar to that of Triassic-Early Jurassic parvipelvians, accessory digits are absent, and notching is present on the leading edge of the first digit. These and other characters indicate exclusion of the Iraq ichthyosaur from Ophthalmosauridae, the only ichthyosaur clade currently known from the Cretaceous. A phylogenetic analysis of Parvipelvia – the largest yet produced – recovers the new taxon as the sister- taxon of Ichthyosaurus communis, thereby invoking a ghost-lineage of over 60 million years. Inclusion of the new taxon in analyses produced by other authors also resulted in exclusion from Ophthalmosauridae, though relationships with other neoichthyosaurians are less resolved than in our analysis. We conclude that the new taxon represents a highly conservative relict – a member of the Ichthyosaurus lineage – that retained an ‘Early Jurassic’ grade of pectoral anatomy into the Cretaceous. Ophthalmosauridae and members of the Ichthyosaurus lineage therefore both persisted beyond the Jurassic. Clearly, both have highly contrasting evolutionary histories and Cretaceous ichthyosaurs do not all represent members of the same evolutionary radiation. The Iraq ichthyosaur is one of several new taxa originally worked on by the late Robert M. Appleby. An inability to resolve conflicting views on the age of the specimen, combined with other issues, derailed his plans to publish on this specimen during the 1970s. [less ▲]

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See detailThe extinction of ichthyosaurs is a facet of a major Cenomanian turnover in marine ecosystems
Fischer, Valentin ULg

Conference (2013, October)

Untangling geosphere-biosphere interactions is crucial to understand the biodiversity and how it might evolve in a changing environment. But little is known about the possible impact of environmental ... [more ▼]

Untangling geosphere-biosphere interactions is crucial to understand the biodiversity and how it might evolve in a changing environment. But little is known about the possible impact of environmental changes on animals occupying the highest levels of the marine trophic chains. The Cretaceous period offers a fantastic opportunity to investigate such relationship, being characterized by a globally warm but changing climate and a diverse assemblage of aquatic reptiles that underwent profound modifications during this period, ultimately permitting the diversification of the animals dominating nowadays marine ecosystems. The origin, magnitude and nature of these turnovers are poorly understood and have rarely been investigated in a global canvas. Especially, how and why ichthyosaurs, the ‘fish-shaped’ marine reptiles, went extinct at the beginning of the Late Cretaceous has been a mystery for decades. Previous assessments of their diversity suggested ichthyosaurs were already on the decline since the end of the Jurassic; their final extinction was therefore regarded as anecdotal. Several theories have proposed unique biological drivers to this event, including a break in the food chain or competition with other marine vertebrates. The reassessment of the taxonomy, phylogeny and paleoecology Cretaceous ichthyosaurs from Eurasia tells a much different story. Ichthyosaurs were ecologically and taxonomically diverse in several Eurasian ecosystems up to the latest Early Cretaceous. This revision also reveals that their extinction is diachronic, being staggered over four phases that span the entire Cenomanian stage. Detailed comparison with other groups suggests the multiphased extinction of ichthyosaurs is not an isolated event, as was previously assumed, but correlates with profound, multiphased turnovers among other marine animals, such as microplankton, rudists, ammonoids, and pythonomorphs. The diversity and contemporaneity of the biotic responses suggest worldwide physicochemical drivers for this profound reorganization of the marine ecosystems. The extinction of ichthyosaurs therefore appears as one of the facets of a much wider event that affected most of the marine ecosystems during the Cenomanian. [less ▲]

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See detailShastasaurid ichthyosaurs and other lost critters from the French Rhaetian
Fischer, Valentin ULg; Goolaerts, Stijn

Conference (2013, September)

Recent advances in the phylogeny and evolution of diversity of ichthyosaurs have recognized a smaller number of more intense turnovers compared to the previous understanding of their evolutionary history ... [more ▼]

Recent advances in the phylogeny and evolution of diversity of ichthyosaurs have recognized a smaller number of more intense turnovers compared to the previous understanding of their evolutionary history. One of these crucial turnovers occurred during the Late Triassic, when all ichthyosaur clades but a minor subset, the parvipelvians, went extinct. The timing and, hence, the severity of this event is however poorly understood and may have been protracted over the entire middle Norian–latest Rhaetian interval, more than 15 million years. The iconic, whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. In 1883, Henry Emile Sauvage (1842–1917), a famous French palaeontologist, described reptilian remains from a Rhaetian bonebed near Autun in eastern France. But this material was subsequently lost and disappeared from the literature. We have re-discovered most of this material in the fossil vertebrates collections of the Katholieke Universteit Leuven, Belgium. Reassessment of this material indicates the presence of very large shastasaurid ichthyosaurs (Ichthyosaurus rheticus, Rachitrema pellati [partim]), probable choristoderes (Actiosaurus gaudryi) and plesiosaurs (Plesiosaurus bibractensis). The occurrence of shastasaurids in Rhaetian strata is corroborated by recent findings in a new locality in southern France. This suggests that the final extinction of this important Triassic clade coincides with the rapid radiation of neoichthyosaurs, forming a short but extremely profound turnover that drastically impacted the evolutionary history of ichthyosaurs. [less ▲]

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See detailA basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs
Fischer, Valentin ULg; Appleby, Robert; Naish, Darren et al

in Biology Letters (2013), 9(20130021), 1-6

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a ... [more ▼]

Cretaceous ichthyosaurs have typically been considered a small, homogeneous assemblage sharing a common Late Jurassic ancestor. Their low diversity and disparity have been interpreted as indicative of a decline leading to their Cenomanian extinction. We describe the first post-Triassic ichthyosaur from the Middle East, Malawania anachronus gen. et sp. nov. from the Early Cretaceous of Iraq, and re-evaluate the evolutionary history of parvipelvian ichthyosaurs via phylogenetic and cladogenesis rate analyses. Malawania represents a basal grade in thunnosaurian evolution that arose during a major Late Triassic radiation event and was previously thought to have gone extinct during the Early Jurassic. Its pectoral morphology appears surprisingly archaic, retaining a forefin architecture similar to that of its Early Jurassic relatives. After the initial latest Triassic radiation of early thunnosaurians, two subsequent large radiations produced lineages with Cretaceous representatives, but the radiation events themselves are pre-Cretaceous. Cretaceous ichthyosaurs therefore include distantly related lineages, with contrasting evolutionary histories, and appear more diverse and disparate than previously supposed. [less ▲]

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See detailMarine vertebrate remains from the Toarcian-Aalenian succession of southern Beaujolais, Rhône, France
Vincent, Peggy; Martin, Jérémy; Fischer, Valentin ULg et al

in Geological Magazine (2013), 150(5), 822834

A previously undocumented marine vertebrate fauna comprising ichthyosaur, plesiosaur, marine crocodilian and fish remains from the Toarcian-Aalenian succession at Lafarge quarry, southern Beaujolais ... [more ▼]

A previously undocumented marine vertebrate fauna comprising ichthyosaur, plesiosaur, marine crocodilian and fish remains from the Toarcian-Aalenian succession at Lafarge quarry, southern Beaujolais, Rhône, France is described on the basis of both historical collections and new discoveries. The taxonomic composition of the Lafarge quarry marine vertebrate assemblage highlights its cosmopolitan nature and strong relationships with taxa known from elsewhere in Europe. Several groups are recorded for the first time in the Toarcian-Aalenian succession of France, implying new palaeobiogeographic interpretations, and prompting discussion of marine amniote diversity during this interval. [less ▲]

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See detailPaléontologie des invertébrés, note de travaux pratiques
Denayer, Julien ULg; Mottequin, Bernard ULg; Poty, Edouard ULg et al

Learning material (2013)

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See detailOrigin, biodiversity, and extinction of Cretaceous ichthyosaurs
Fischer, Valentin ULg

Doctoral thesis (2013)

Ichthyosauria is a group of reptiles that colonized numerous niches in Mesozoic marine ecosystems. Their Cretaceous representatives were however regarded as undiversified, especially compared to their ... [more ▼]

Ichthyosauria is a group of reptiles that colonized numerous niches in Mesozoic marine ecosystems. Their Cretaceous representatives were however regarded as undiversified, especially compared to their Triassic and Jurassic ancestors, because only a few species are regarded as valid in the Cretaceous. Besides, most of them belong to a single genus, Platypterygius, whose taxonomy and phylogeny are problematic. Therefore, Cretaceous ichthyosaurs have been widely considered as the last members of a group on the decline, although the timing, the cause and the magnitude of their extinction phases greatly vary among authors. Yet, a great part of the Cretaceous ichthyosaur record, the Eurasian material, has been neglected from more than 100 years; theories explaining the evolution of the last ichthyosaurs therefore miss the biggest part of the picture. Notably, how ichthyosaurs diversified and went extinct during the Cretaceous is basically unknown. To tackle these topics, I assess the taxonomy of Cretaceous ichthyosaurs from Eurasia, test their phylogenetic position within a global analysis of post-Triassic ichthyosaurs, evaluate their ecological diversity and analyse their phases of radiation and extinction. Assessment of the Eurasian material led to the discovery of seven new taxa (“Iraq animal”, Acamptonectes densus, “Lenin Form”, Sveltonectes insolitus, Sveltonectes “Ebbo Form”, “Sisteron Form”, “Colossal Form”) and the re-installation of several other taxa as valid (Simbirskiasaurus birjukovi, P. bannovkensis, Cetarthrosaurus walkeri, P. hercynicus). Morphological and phylogenetic evidence suggest Platypterygius hides a very large generic diversity and should be limited to its type species P. platydactylus; however, the interrelationships of the large platypterygiine ichthyosaurs from the Aptian–Cenomanian interval are poorly constrained. Phylogenetic analyses provide robust evidence for disparate origins of Cretaceous ichthyosaurs; these animals actually belonged to three distinct clades that diverged several tens of million years before the Cretaceous. These three clades had contrasted evolutionary histories and colonized disctinct ecological niches during the Cretaceous. Survival and extinction rates demonstrate ichthyosaurs suffered no extinction event at the Jurassic–Cretaceous boundary. They were therefore highly diverse during the Cretaceous, although the sampling of some stages remains inadequate. Notably, up to eight genera were present during the late Albian, a few million years before their final extinction. This extinction appears staggered over four phases that span the entire Cenomanian stage; it also forms one of the facets of a much wider event that affected most levels of marine trophic chains during the Cenomanian. Compilation of published data and collaborations with other specialists show that the radiation of snakes, mosasaurs, and numerous lineages of modern fishes, the severe extinctions among cephalopods and rudist bivalves and the complete extinction of ichthyosaurs likely belong to the same global turnover event. The magnitude, diversity and simultaneity of the biotic responses strongly suggest that global physico-chemical factors triggered this profound reorganization of the marine ecosystems, notably the conjunction of a rather brutal onset of extremely high temperatures and sea level, intense marine volcanism and phases of worldwide ocean anoxia. [less ▲]

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See detailLes reptiles marins de France face aux bouleversements crétacés
Fischer, Valentin ULg

Conference given outside the academic context (2012)

Il y a plus de 100 millions d’années, l’Europe est un vaste archipel au sein d’une mer chaude et relativement peu profonde. Si les dinosaures dominent alors les terres émergées, le sommet de la chaîne ... [more ▼]

Il y a plus de 100 millions d’années, l’Europe est un vaste archipel au sein d’une mer chaude et relativement peu profonde. Si les dinosaures dominent alors les terres émergées, le sommet de la chaîne alimentaire des écosystèmes marins est occupé par des reptiles parfaitement adaptés au milieu aquatique tels que les plésiosaures, les crocodiles marins et les ichthyosaures. Des (re)découvertes françaises récentes ont considérablement augmenté la diversité et notre compréhension de l’écologie de ces reptiles, notamment les ichthyosaures. Cependant, les gisements français–et eurasiatiques–en général recèlent également la trace d’une profonde perturbation climatique mondiale qui va bousculer ces écosystèmes et provoquer l’extinction des ichthyosaures, après un règne de plus de 150 millions d’années. [less ▲]

Detailed reference viewed: 37 (7 ULg)
See detailUsing ghost rock weathering as a new tool for quarry management
Fischer, Valentin ULg; Vergari, Anne

Conference (2012, October)

Although karstic weathering (sensu lato) is a major concern for the exploitation of limestone quarries, the importance, spatial extension, and intensity of this natural phenomenon are rarely investigated ... [more ▼]

Although karstic weathering (sensu lato) is a major concern for the exploitation of limestone quarries, the importance, spatial extension, and intensity of this natural phenomenon are rarely investigated because of the lack of applicable technique to assess these variables other than subsurface geophysical exploration methods. Here, we propose to use the intrinsic property of ghost-rock weathering, tectonic control, to predict the degree and type of weathering of the reserve of two contiguous limestone quarries in the Tournai area (western Belgium). First, we revised the macrotectonic setting of these quarries, creating five tectonic entities. Then, we built an extensive fracture database (1357 ‘events’), recording fracture direction, dip, width, height, mineralization, and weathering. Then, we calculated a “Sterile Index” that is a simple function of the relative occurrence and mean width of karstified fractures. The rose diagrams of fracture orientations are contrasted between tectonic entities and so are the intensity and the dominant type of weathering: tectonic entities with widely dispersed fracture directions are significantly more weathered than entities with narrowly dispersed rose diagrams. Preliminary tests indicate fracture orientation and weathering are consistent within the tectonic entities, allowing extrapolation to quarries reserves. Ultimately, this technique can be used to predict the rock waste volume of the quarries reserves (when combined with geophysical exploration methods) and manage the development of the quarries accordingly. [less ▲]

Detailed reference viewed: 40 (5 ULg)