The Experts below are selected from a list of 510 Experts worldwide ranked by ideXlab platform
Sylvain Adnet - One of the best experts on this subject based on the ideXlab platform.
-
A shark fauna from the Campanian of Hornby Island, British Columbia, Canada: an insight into the diversity of Cretaceous deep-water assemblages
Historical Biology, 2019Co-Authors: Henri Cappetta, Kurt Morrison, Sylvain AdnetAbstract:This article describes a rich and diversified elasmobranch fauna collected from the Upper Campanian Northumberland Formation, a part of the Nanaimo Group, exposed on Hornby Island, British Columbia, Canada. This fauna consists of 30 species belonging to 26 genera and is characterised by a large number of new elasmobranch taxa (17 species, 7 genera and 2 families); all these principally belong to the usual deep-water squalomorphs (e.g. Chlamydoselachiformes, Hexanchiformes, Echinorhiniformes, Squaliformes, Pristiophoriformes). This elasmobranch association displays two striking features: no batoid taxa have been found despite the extremely fine process of collection, and it is mainly composed of taxa living in a deep-water environment. The identified species have a large panel of body size estimated between about 50 cm (Eoetmopterus?) up to probably 3 to 4 metres long (eg. Xampylodon nov. gen., Carcharias) and maybe more for Dykeius nov. gen. The Hornby Island fauna represents by far the most diverse deep-water assemblage ever described in the Late Cretaceous, particularly rich in hexanchiforms and squaliforms, providing new insights into the history of the deep-water settlement of this period. ARTICLE HISTORY
-
A new shark and ray fauna from the Middle Miocene of Mazan, Vaucluse (southern France) and its importance in interpreting the paleoenvironment of marine deposits in the southern Rhodanian Basin
Swiss Journal of Palaeontology, 2011Co-Authors: Nicolas Vialle, Sylvain Adnet, Henri CappettaAbstract:Recent paleontological excavations of the Middle Miocene sandstones (top of the “Schlier” facies) near Mazan, Vaucluse (southern France) uncovered a rich selachian teeth assemblage including 34 shark and ray species. This great diversity of selachian taxa provides new information about the palaeoenvironmental settings of some Middle Miocene deposits in the southern Rhodanian basin. For instance, the co-occurrence of some deepwater Squaliformes and Rajidae with numerous Carcharhiniformes and Myliobatiformes, usually inhabiting the continental shelf, suggests a deepwater deposit inshore, as adjacent to a submarine canyon area.
-
A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes: Squaliformes) based on dental characters
Lethaia, 2007Co-Authors: Sylvain Adnet, Henri CappettaAbstract:Squaliformes comprise the major proportion of modern deep-water sharks, yet their fossil history and phylogenetic relationships are still poorly understood. New analyses have been undertaken, however, and new living and fossil species have been discovered during the past 10 years. A cladistic analysis involving 29 dental characters has been made and most living and fossil genera are included. On the basis of their dental morphology, the monophyly of the Squaliformes can be supported if the fossil genus Protospinax is excluded. The traditional phylogenetic positions of most living genera, Protosqualus, Cretascymnus and Eoetmopterus, are confirmed despite the fact that the Oxynotidae, Etmopterinae, Palaeomicroides, Proetmopterus and Microetmopterus have some atypical phylogenetic relationships within the Squaliformes. The addition of the palaeontological data in a phylogenetic tree including fossil and living Squaliformes demonstrates some gaps in the fossil record. Nevertheless, and as a consequence of that stratigraphy-phylogeny inference, two particular events can be pinpointed in the history of the Squaliformes: the first one occurs after the major Cenomanian-Turonian anoxic event and the second one after the Cretaceous/Tertiary crisis. The first radiation involves the majority of the living Squaliformes (Somniosinae, Centrophorinae, most of the Etmopterinae, Oxynotinae) in deep-sea waters, the second, the more epipelagic sharks (most of the Dalatiidae), suggesting a secondary adaptation to more shallow environments.
-
Dentition of etmopterid shark Miroscyllium (Squaliformes) with comments on the fossil record of lanternsharks
Cybium : Revue Internationale d’Ichtyologie, 2006Co-Authors: Sylvain Adnet, Henri Cappetta, Kazuhiro NakayaAbstract:Although modern lantern sharks (Etmopteridae, Squaliformes) are taxonomically diverse, their phylogenetic relationships remain unclear. Numerous fossil etmopterids have been recently discovered, and their geologic occurrences are reviewed here. The dentition of the rare recent etmopterid Miroscyllum sheikoi is described. The species shows peculiar ontogenetic changes in the morphology of lower and upper teeth, and allows to assign some fossil material described as Centroscyllium by Ledoux (1972) to Miroscyllium. Moreover, the presence, in Miroscyllium sheikoi, of a morphological transitional dental type between Etmopterus and Centroscyllium, and its discovery in the fossil record allow to propose an alternative way to contribute to the phylogenetic frameworks.
-
Nouveaux genres de Squaliformes (Chondrichthyes) du Paléogène des Landes (Sud-Ouest de la France)
Paläontologische Zeitschrift, 2006Co-Authors: Sylvain Adnet, Henri Cappetta, Jozef ReyndersAbstract:Parmi les nombreux Squaliformes récoltés dans le Lutétien des Landes (SO de la France), deux genres et espèces nouveaux ont été reconnus: Squaliodalatias weltoni n. gen. n. sp. et Angoumeius paradoxus n. gen. n. sp. La morphologie dentaire du premier permet de le rapprocher des Dalatiidae. Les relations phylétiques du second taxon sont pour 1’instant moins claires, en raison de sa denture supérieure inhabituelle pour un Dalatiiforme aussi évolué au niveau de la denture inférieure. Ces taxa nouveaux viennent enrichir nos connaissances sur un groupe encore mal connu à l’état fossile en raison de son habitat bathyal ainsi que sur la mise en place et la radiation, encore trop peu documentée, des faunes profondes. Among the numerous Squaliformes collected in the Lutetian of the Landes department (southwestern France), two new genera and species are recognized: Squaliodalatias weltoni n. gen. n. sp. and Angoumeius paradoxus n. gen. n. sp. The dental morphology of the first one allows to place it close to the Dalatiidae. The phyletic relationships of the second taxon are less clear for the moment, because of its Upper dentition which is unusual for such an advanced dalatiiform at the level of the lower dentition. These new taxa increase our knowledge on a group still poorly known in the fossil State because of its bathyal habitat, as well as on the radiation of deep water faunas, still too little documented.
Joan Navarro - One of the best experts on this subject based on the ideXlab platform.
-
unravelling the ecological role and trophic relationships of uncommon and threatened elasmobranchs in the western mediterranean sea
Marine Ecology Progress Series, 2015Co-Authors: Claudio Barria, Marta Coll, Joan NavarroAbstract:Deficiencies in basic ecological information on uncommon and endangered elasmobranch fishes impair the assessment of their ecological role in marine ecosystems. In this study, we examined the feeding ecology (diet composition and trophic level) and trophic relationships of 22 elasmobranchs (2 Carcharhiniformes, 1 Hexanchiformes, 1 Lamniformes, 3 Myliobatiformes, 6 Rajiformes, 6 Squaliformes and 3 Torpediniformes) present in the western Mediterranean Sea. To obtain a comprehensive view of the feeding ecology of these species, we combined different approaches: stable isotope analyses (delta C-13 and delta N-15 values), stomach content analyses and published sources. Our results revealed differences in feeding strategies among elasmobranch groups: skates (Rajiformes) mainly consume crustaceans; sharks (Carcharhiniformes, Hexanchiformes, Squaliformes and Lamniformes) prefer mixed diets composed of cephalopods, crustaceans and fishes; electric rays (Torpediniformes) feed mostly on fishes; and the diet of stingrays (Myliobatiformes) varies between species. Sharks and electric rays show higher trophic positions than skates, and the former occupy similar positions to other apex predators. Skates are more similar to other mesopredator fishes. These new findings offer essential information on the ecological role of several elasmobranchs in the western Mediterranean Sea and provide useful data for managers for future conservation strategies.
Henri Cappetta - One of the best experts on this subject based on the ideXlab platform.
-
A shark fauna from the Campanian of Hornby Island, British Columbia, Canada: an insight into the diversity of Cretaceous deep-water assemblages
Historical Biology, 2019Co-Authors: Henri Cappetta, Kurt Morrison, Sylvain AdnetAbstract:This article describes a rich and diversified elasmobranch fauna collected from the Upper Campanian Northumberland Formation, a part of the Nanaimo Group, exposed on Hornby Island, British Columbia, Canada. This fauna consists of 30 species belonging to 26 genera and is characterised by a large number of new elasmobranch taxa (17 species, 7 genera and 2 families); all these principally belong to the usual deep-water squalomorphs (e.g. Chlamydoselachiformes, Hexanchiformes, Echinorhiniformes, Squaliformes, Pristiophoriformes). This elasmobranch association displays two striking features: no batoid taxa have been found despite the extremely fine process of collection, and it is mainly composed of taxa living in a deep-water environment. The identified species have a large panel of body size estimated between about 50 cm (Eoetmopterus?) up to probably 3 to 4 metres long (eg. Xampylodon nov. gen., Carcharias) and maybe more for Dykeius nov. gen. The Hornby Island fauna represents by far the most diverse deep-water assemblage ever described in the Late Cretaceous, particularly rich in hexanchiforms and squaliforms, providing new insights into the history of the deep-water settlement of this period. ARTICLE HISTORY
-
A new shark and ray fauna from the Middle Miocene of Mazan, Vaucluse (southern France) and its importance in interpreting the paleoenvironment of marine deposits in the southern Rhodanian Basin
Swiss Journal of Palaeontology, 2011Co-Authors: Nicolas Vialle, Sylvain Adnet, Henri CappettaAbstract:Recent paleontological excavations of the Middle Miocene sandstones (top of the “Schlier” facies) near Mazan, Vaucluse (southern France) uncovered a rich selachian teeth assemblage including 34 shark and ray species. This great diversity of selachian taxa provides new information about the palaeoenvironmental settings of some Middle Miocene deposits in the southern Rhodanian basin. For instance, the co-occurrence of some deepwater Squaliformes and Rajidae with numerous Carcharhiniformes and Myliobatiformes, usually inhabiting the continental shelf, suggests a deepwater deposit inshore, as adjacent to a submarine canyon area.
-
A palaeontological and phylogenetical analysis of squaliform sharks (Chondrichthyes: Squaliformes) based on dental characters
Lethaia, 2007Co-Authors: Sylvain Adnet, Henri CappettaAbstract:Squaliformes comprise the major proportion of modern deep-water sharks, yet their fossil history and phylogenetic relationships are still poorly understood. New analyses have been undertaken, however, and new living and fossil species have been discovered during the past 10 years. A cladistic analysis involving 29 dental characters has been made and most living and fossil genera are included. On the basis of their dental morphology, the monophyly of the Squaliformes can be supported if the fossil genus Protospinax is excluded. The traditional phylogenetic positions of most living genera, Protosqualus, Cretascymnus and Eoetmopterus, are confirmed despite the fact that the Oxynotidae, Etmopterinae, Palaeomicroides, Proetmopterus and Microetmopterus have some atypical phylogenetic relationships within the Squaliformes. The addition of the palaeontological data in a phylogenetic tree including fossil and living Squaliformes demonstrates some gaps in the fossil record. Nevertheless, and as a consequence of that stratigraphy-phylogeny inference, two particular events can be pinpointed in the history of the Squaliformes: the first one occurs after the major Cenomanian-Turonian anoxic event and the second one after the Cretaceous/Tertiary crisis. The first radiation involves the majority of the living Squaliformes (Somniosinae, Centrophorinae, most of the Etmopterinae, Oxynotinae) in deep-sea waters, the second, the more epipelagic sharks (most of the Dalatiidae), suggesting a secondary adaptation to more shallow environments.
-
Dentition of etmopterid shark Miroscyllium (Squaliformes) with comments on the fossil record of lanternsharks
Cybium : Revue Internationale d’Ichtyologie, 2006Co-Authors: Sylvain Adnet, Henri Cappetta, Kazuhiro NakayaAbstract:Although modern lantern sharks (Etmopteridae, Squaliformes) are taxonomically diverse, their phylogenetic relationships remain unclear. Numerous fossil etmopterids have been recently discovered, and their geologic occurrences are reviewed here. The dentition of the rare recent etmopterid Miroscyllum sheikoi is described. The species shows peculiar ontogenetic changes in the morphology of lower and upper teeth, and allows to assign some fossil material described as Centroscyllium by Ledoux (1972) to Miroscyllium. Moreover, the presence, in Miroscyllium sheikoi, of a morphological transitional dental type between Etmopterus and Centroscyllium, and its discovery in the fossil record allow to propose an alternative way to contribute to the phylogenetic frameworks.
-
Nouveaux genres de Squaliformes (Chondrichthyes) du Paléogène des Landes (Sud-Ouest de la France)
Paläontologische Zeitschrift, 2006Co-Authors: Sylvain Adnet, Henri Cappetta, Jozef ReyndersAbstract:Parmi les nombreux Squaliformes récoltés dans le Lutétien des Landes (SO de la France), deux genres et espèces nouveaux ont été reconnus: Squaliodalatias weltoni n. gen. n. sp. et Angoumeius paradoxus n. gen. n. sp. La morphologie dentaire du premier permet de le rapprocher des Dalatiidae. Les relations phylétiques du second taxon sont pour 1’instant moins claires, en raison de sa denture supérieure inhabituelle pour un Dalatiiforme aussi évolué au niveau de la denture inférieure. Ces taxa nouveaux viennent enrichir nos connaissances sur un groupe encore mal connu à l’état fossile en raison de son habitat bathyal ainsi que sur la mise en place et la radiation, encore trop peu documentée, des faunes profondes. Among the numerous Squaliformes collected in the Lutetian of the Landes department (southwestern France), two new genera and species are recognized: Squaliodalatias weltoni n. gen. n. sp. and Angoumeius paradoxus n. gen. n. sp. The dental morphology of the first one allows to place it close to the Dalatiidae. The phyletic relationships of the second taxon are less clear for the moment, because of its Upper dentition which is unusual for such an advanced dalatiiform at the level of the lower dentition. These new taxa increase our knowledge on a group still poorly known in the fossil State because of its bathyal habitat, as well as on the radiation of deep water faunas, still too little documented.
Claudio Barria - One of the best experts on this subject based on the ideXlab platform.
-
unravelling the ecological role and trophic relationships of uncommon and threatened elasmobranchs in the western mediterranean sea
Marine Ecology Progress Series, 2015Co-Authors: Claudio Barria, Marta Coll, Joan NavarroAbstract:Deficiencies in basic ecological information on uncommon and endangered elasmobranch fishes impair the assessment of their ecological role in marine ecosystems. In this study, we examined the feeding ecology (diet composition and trophic level) and trophic relationships of 22 elasmobranchs (2 Carcharhiniformes, 1 Hexanchiformes, 1 Lamniformes, 3 Myliobatiformes, 6 Rajiformes, 6 Squaliformes and 3 Torpediniformes) present in the western Mediterranean Sea. To obtain a comprehensive view of the feeding ecology of these species, we combined different approaches: stable isotope analyses (delta C-13 and delta N-15 values), stomach content analyses and published sources. Our results revealed differences in feeding strategies among elasmobranch groups: skates (Rajiformes) mainly consume crustaceans; sharks (Carcharhiniformes, Hexanchiformes, Squaliformes and Lamniformes) prefer mixed diets composed of cephalopods, crustaceans and fishes; electric rays (Torpediniformes) feed mostly on fishes; and the diet of stingrays (Myliobatiformes) varies between species. Sharks and electric rays show higher trophic positions than skates, and the former occupy similar positions to other apex predators. Skates are more similar to other mesopredator fishes. These new findings offer essential information on the ecological role of several elasmobranchs in the western Mediterranean Sea and provide useful data for managers for future conservation strategies.
Amelia M Connell - One of the best experts on this subject based on the ideXlab platform.
-
trophic interactions and distribution of some squaliforme sharks including new diet descriptions for deania calcea and squalus acanthias
PLOS ONE, 2013Co-Authors: Matthew R Dunn, Darren W Stevens, Jeffrey S Forman, Amelia M ConnellAbstract:Squaliforme sharks are a common but relatively vulnerable bycatch in many deep water fisheries. Eleven species of squaliforme shark are commonly caught at depths of 200–1200 m on Chatham Rise, New Zealand, and their diversity suggests they might occupy different niches. The diets of 133 Deania calcea and 295 Squalus acanthias were determined from examination of stomach contents. The diet of D. calcea was characterised by mesopelagic fishes, and S. acanthias by benthic to pelagic fishes, but was more adaptive and included likely scavenging. Multivariate analyses found the most important predictors of diet variability in S. acanthias were year, bottom temperature, longitude, and fish weight. The diet of the nine other commonly caught squaliforme sharks was reviewed, and the spatial and depth distribution of all species on Chatham Rise described from research bottom trawl survey catches. The eleven species had a variety of different diets, and depth and location preferences, consistent with niche separation to reduce interspecific competition. Four trophic groups were identified, characterised by: mesopelagic fishes and invertebrates (Centroselachus crepidater, D. calcea, and Etmopterus lucifer); mesopelagic and benthopelagic fishes and invertebrates (Centroscymnus owstoni, Etmopterus baxteri); demersal and benthic fishes (Centrophorus squamosus, Dalatias licha, Proscymnodon plunketi); and a generalist diet of fishes and invertebrates (S. acanthias). The trophic levels of the species in each of the four groups were estimated as 4.18–4.24, 4.20–4.23, 4.24–4.48, and 3.84 respectively. The diet of Oxynotus bruniensis and Squalus griffini are unknown. The different niches occupied by different species are likely to influence their vulnerability to bottom trawl fisheries. Some species may benefit from fisheries through an increased availability of scavenged prey.
