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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 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 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 ▲]

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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 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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