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Nathalie Bardet - One of the best experts on this subject based on the ideXlab platform.
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virtual reexamination of a plesiosaurian specimen reptilia plesiosauria from the late cretaceous turonian of goulmima morocco using computed tomography
Journal of Vertebrate Paleontology, 2017Co-Authors: Remi Allemand, Nathalie Bardet, Alexandra Houssaye, Peggy VincentAbstract:ABSTRACT Turonian deposits of the Goulmima area, Er-Rachidia Province in southern Morocco, have yielded a diverse Marine Vertebrate fauna, including chondrichthyans, bony fishes, and large Marine reptiles such as plesiosaurians, mosasauroids, and turtles. These fossils are included in ovoid calcareous nodules that are difficult to prepare. Moreover, bones may be partially or totally dissolved, making their study difficult. Using computed tomography, we have reconstructed the entire skull anatomy of SMNS 81783, one of the rare plesiosaurian specimens found in this locality and more generally in Africa. The digital three-dimensional reconstruction of the skull and the mandible offers for the first time the possibility to describe this specimen exhaustively. The new anatomical characters recorded confirm that SMNS 81783 belongs to Elasmosauridae on the basis of (1) slender and triangular skull; (2) beak index equal to 42%; (3) temporal fossa estimated to occupy about 40% of the skull length; (4) long process...
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virtual reexamination of a plesiosaurian specimen reptilia plesiosauria from the late cretaceous turonian of goulmima morocco using computed tomography
Journal of Vertebrate Paleontology, 2017Co-Authors: Remi Allemand, Nathalie Bardet, Alexandra Houssaye, Peggy VincentAbstract:Turonian deposits of the Goulmima area, Er-Rachidia Province in southern Morocco, have yielded a diverse Marine Vertebrate fauna, including chondrichthyans, bony fishes, and large Marine reptiles such as plesiosaurians, mosasauroids, and turtles. These fossils are included in ovoid calcareous nodules that are difficult to prepare. Moreover, bones may be partially or totally dissolved, making their study difficult. Using computed tomography, we have reconstructed the entire skull anatomy of SMNS 81783, one of the rare plesiosaurian specimens found in this locality and more generally in Africa. The digital three-dimensional reconstruction of the skull and the mandible offers for the first time the possibility to describe this specimen exhaustively. The new anatomical characters recorded confirm that SMNS 81783 belongs to Elasmosauridae on the basis of (1) slender and triangular skull; (2) beak index equal to 42%; (3) temporal fossa estimated to occupy about 40% of the skull length; (4) long process of the premaxillae extending posteriorly to meet the parietal above the orbit and separating the frontals; and (5) margin of the temporal fenestra lacking obvious contribution from the frontal. A preliminary phylogenetic analysis confirms its elasmosaurid affinity. The relationships between SMNS 81783, Libonectes atlasense, and Libonectes morgani, as well as the presence of stapes and pineal foramen, are discussed.
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late cretaceous continental and Marine Vertebrate assemblages from the lano quarry basque cantabrian region iberian peninsula an update
Journal of Iberian Geology, 2015Co-Authors: Xabier Pereda Suberbiola, Nathalie Bardet, Henri Cappetta, Jose Carmelo Corral, Humberto Astibia Ayerra, Ainara Badiola Kortabitarte, Ana Berreteaga Escudero, Eric Buffetaut, Angela D Buscalioni, Lionel CavinAbstract:The Vertebrate-bearing beds of the Lano quarry (Condado de Trevino) are among the most relevant sites from the Late Cretaceous of Europe. Geologically, Lano and the adjacent region are set on the southern limb of the South-Cantabrian Synclinorium (SE Basque-Cantabrian Region, northern Iberian Peninsula). The Lano sites were discovered in 1984; thousands of bones and teeth, including microfossils, have been collected during the prospection in the field and excavation campaigns. The Vertebrate remains occur at two different stratigraphic horizons within a continental to shallow Marine succession of Late Campanian-Maastrichtian age. The lower horizon contains the Lano 1 and Lano 2 sites, whereas the upper horizon contains the Albaina site. In the Lano sites, three fossiliferous beds (called L1A, L1B and L2) are known within an alluvial system composed mainly of fluvial sands and silts. The sedimentary structures are consistent with channel areas within an extensive braided river system. Based mainly on stratigraphic correlations, the fluvial beds of Lano are regarded as Late Campanian to Early Maastrichtian in age. These deposits have yielded a very diverse Vertebrate assemblage, which consists of nearly 40 species, including actinopterygians, lissamphibians, lepidosaurs, turtles, crocodyliforms, dinosaurs, pterosaurs, and mammals. Seven genera and ten species have been erected to date in Lano. With reference to the Marine Vertebrate association of Albaina, it consists of at least 37 species, including sharks and rays, actinopterygians, mosasaurids, and plesiosaurs. Two genera and species of rhinobatoids (family indet.) and two new species of rhinobatids have been erected in Albaina. The fossil association indicates a Late (but not latest) Maastrichtian age. Recently, isolated turtle and dinosaur fossils have been discovered in the sublittoral beds of Albaina. The Lano quarry is one of the most noteworthy Campanian-Maastrichtian Vertebrate localities of Europe by its taxonomic diversity, and provides useful information about the composition and affinities of both continental and Marine Vertebrate faunas from the latest Cretaceous of southwestern Europe.
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Marine Vertebrate faunas from the maastrichtian phosphates of benguerir ganntour basin morocco biostratigraphy palaeobiogeography and palaeoecology
Palaeogeography Palaeoclimatology Palaeoecology, 2014Co-Authors: Henri Cappetta, Nathalie Bardet, Xabier Pereda Suberbiola, Sylvain Adnet, Driss Akkrim, Mohamed Amalik, Aziza BenabdallahAbstract:Abstract The Maastrichtian of Benguerir (eastern part of the Ganntour Basin, Morocco) consists of about 20 m of phosphates displaying an alternance of soft phosphate levels, marly horizons and hard phosphatic limestones. Isolated teeth of selachians, actinopterygians and Marine reptiles are extremely numerous in these phosphatic deposits and have been used for biostratigraphical, palaeodiversity and palaeoecological purposes. Detailed field work allowed to establish an exhaustive list of the Benguerir Marine Vertebrate faunas with their biostratigraphical distribution through five main fossiliferous levels (L6 to L2) spanning all the Maastrichtian. Their importance for biochronological purposes and correlations with other Maastrichtian phosphate deposits worldwide appears noteworthy. The selachians are currently represented by 60 species belonging to 32 genera and 7 orders. Among them, the genus Squalicorax is one of the most interesting concerning high-resolution biostratigraphy and correlations with other phosphate basins because of important rates of change noted between the 5 species recovered from base (e.g. occurrence of S. africanus ) to top (e.g. strong representation of S. pristodontus ) of the Maastrichtian. The Marine reptiles include mainly mosasaurids but also scarcer plesiosaurs, chelonians and crocodyliforms, representing at least 14 taxa. The mosasaurid squamates are the most abundant and diversified with at least 8 species ranging all along the succession. The actinopterygians include mainly teleosts but also pycnodonts, also common in all levels and representing at least 7 taxa. Selachians and reptiles show the same trends, in terms of species richness per level, even if the reptiles are less informative due to a less diversified assemblage. For sharks, L6 and L2 show a high percentage of genera and species occurring only in the layer concerned. The evolution of diversity in actinopterygian fishes is less clear because of their low diversity. The use of dissimilarity indices and agglomerative method underscores two distinct associations: a lower one including the levels L6 and L5, and an upper one comprising the levels L4 to L2. These two associations allow to separate a lower and an upper Maastrichtian level and are important for correlations all around the southern and eastern margins of the Tethys. Another clear faunal turnover occurs between L3 and L2, because of a high appearance rate in L2 (at least in sharks) suggesting an increase in prey abundance, as testified by the rapid increase of Marine predator density. Indeed, and through L6 to L2, a possible signal of an environmental damage affecting the predator community can be noted by faunal turnovers, even if no significant change in prey association was clearly detected. From a palaeobiogeographical point of view, the faunal associations of Benguerir appear typical of the southern and eastern margins of the Tethys, with several typical species not occurring in the northern Tethys.
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zarafasaura oceanis a new elasmosaurid reptilia sauropterygia from the maastrichtian phosphates of morocco and the palaeobiogeography of latest cretaceous plesiosaurs
Gondwana Research, 2011Co-Authors: Peggy Vincent, Nathalie Bardet, X. Pereda Suberbiola, Baâdi Bouya, Mbarek Amaghzaz, Said MeslouhAbstract:Abstract Though the Maastrichtian Phosphates of Morocco have yielded very rich Marine Vertebrate assemblages, plesiosaurs remain very scarce in these strata. The only hitherto recognized taxon was Plesiosaurus mauritanicus Arambourg, 1952 , regarded here as a nomem dubium . Here we describe a new genus and species of elasmosaurid plesiosaur, Zarafasaura oceanis , which represents the first valid elasmosaurid plesiosaur described from the latest Cretaceous of Africa, and the second one from this continent. A phylogenetic analysis of plesiosauroids indicates that Zarafasaura oceanis has close affinities with elasmosaurids from the Late Cretaceous of North America and Japan. Among its distinctive suite of characters, the general shape and organisation of its squamosal and palate are unique among elasmosaurids. This new taxon completes our understanding of Late Cretaceous plesiosaur palaeobiodiversity and palaeobiogeography, and shows that Maastrichtian plesiosaurs were characterized by a quite high degree of endemism. They were also highly diversified and distributed worldwide, which supports the hypothesis of a catastrophic extinction of plesiosaurs at the K/T boundary.
Graeme C Hays - One of the best experts on this subject based on the ideXlab platform.
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quantifying wildlife watching ecotourism intensity on an endangered Marine Vertebrate
Animal Conservation, 2015Co-Authors: Gail Schofield, Rebecca Scott, Kostas A Katselidis, Antonios D Mazaris, Graeme C HaysAbstract:Here, we show how seasonal changes in animal density drive strategic shifts in the activities of wildlife-watching operators. These shifts result in high viewing intensity when animal densities are low, highlighting the need for modifications to existing wildlife-watching guidelines. We used the endangered loggerhead sea turtle Caretta caretta as a model species that exhibits staggered departure from an important breeding area (Zakynthos, Greece, Mediterranean) over a 2-month period (July to August) when tourism is at a peak, to investigate changes in wildlife-watching strategies, zoning effectiveness and voluntary guideline compliance over time. We used a combination of direct land-based observations, global positioning system tracking (of wildlife-watching vessels and turtles) and models. The modelled number of turtles present in the breeding area decreased from > 200 in July to < 50 in August, while the intensity of turtle-viewing increased from a mean 1.5 to 6.1 wildlife-watching vessels per turtle-viewing event (i.e. concurrent and consecutive vessels observing a single turtle) over the same period, respectively. During this period, the wildlife-watching strategy changed and compliance to guidelines reduced (exacerbated by recreational vessels). However, wildlife-watching activity was limited to a highly restricted 0.95-km2 nearshore area, overlapping with just 9.5% of the core habitat area used by turtles. Our results have broad implications (whale watching etc.) by showing the importance of taking the number of animals available for viewing into consideration when assessing wildlife-watching activity and when designing viewing guidelines, particularly for populations where numbers noticeably fluctuate.
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convergent evolution in locomotory patterns of flying and swimming animals
Nature Communications, 2011Co-Authors: Adrian C Gleiss, Graeme C Hays, Salvador J Jorgensen, Nikolai Liebsch, Juan Emilio Sala, Brad Norman, Flavio Quintana, Edward Grundy, Claudio CampagnaAbstract:Locomotion is one of the major energetic costs faced by animals and various strategies have evolved to reduce its cost. Birds use interspersed periods of flapping and gliding to reduce the mechanical requirements of level flight while undergoing cyclical changes in flight altitude, known as undulating flight. Here we equipped free-ranging Marine Vertebrates with accelerometers and demonstrate that gait patterns resembling undulating flight occur in four Marine Vertebrate species comprising sharks and pinnipeds. Both sharks and pinnipeds display intermittent gliding interspersed with powered locomotion. We suggest, that the convergent use of similar gait patterns by distinct groups of animals points to universal physical and physiological principles that operate beyond taxonomic limits and shape common solutions to increase energetic efficiency. Energetically expensive large-scale migrations performed by many Vertebrates provide common selection pressure for efficient locomotion, with potential for the convergence of locomotory strategies by a wide variety of species.
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a novel technique for measuring heart rate in a free swimming Marine Vertebrate
Journal of Experimental Marine Biology and Ecology, 2007Co-Authors: Andrew E Myers, Graeme C HaysAbstract:A mouth opening sensor incorporating a magnet and Hall sensor attached to a data logging unit was used to monitor the breathing and foraging behavior of a free-swimming leatherback sea turtle (Dermochelys coriacea). Analysis of these data revealed a rhythmic low amplitude oscillation. Further investigation of the frequency of this signal lead us to believe that the movements (b0.1 mm) are caused by the movement of blood through the nearby blood vessels. Putative heart rate decreased during dive descent and increased considerably during dive ascent reflecting the bradycardia and anticipatory tachycardia recorded by other means in other air-breathing divers. Oscillation frequencies were also comparable to the heart rate recorded in leatherbacks by means of implanted electrodes. We therefore propose that this device which was already known to reliably record behaviour such as breathing, feeding and buccal oscillations in sea turtles also has potential for recording other signals which cause movement on the external surface of an animal. © 2007 Elsevier B.V. All rights reserved.
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thermal niche large scale movements and implications of climate change for a critically endangered Marine Vertebrate
Global Change Biology, 2006Co-Authors: Clive R Mcmahon, Graeme C HaysAbstract:Climate change is expected to have a number of impacts on biological communities including range extensions and contractions. Recent analyses of multidecadal data sets have shown such monotonic shifts in the distribution of plankton communities and various fish species, both groups for which there is a large amount of historical data on distribution. However, establishing the implications of climate change for the range of endangered species is problematic as historic data are often lacking. We therefore used a different approach to predict the implications of climate change for the range of the critically endangered planktivourous leatherback turtle (Dermochelys coriacea). We used long-term satellite telemetry to define the habitat utilization of this species. We show that the northerly distribution limit of this species can essentially be encapsulated by the position of the 15°C isotherm and that the summer position of this isotherm has moved north by 330 km in the North Atlantic in the last 17 years. Consequently, conservation measures will need to operate over ever-widening areas to accommodate this range extension.
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first records of dive durations for a hibernating sea turtle
Biology Letters, 2005Co-Authors: Flegra Bentivegna, Sandra Hochscheid, Graeme C HaysAbstract:The first published record, from the early 1970s, of hibernation in sea turtles is based on the reports of the indigenous Indians and fishermen from Mexico, who hunted dormant green turtles (Chelonia mydas) in the Gulf of California. However, there were no successful attempts to investigate the biology of this particular behaviour further. Hence, data such as the exact duration and energetic requirements of dormant winter submergences are lacking. We used new satellite relay data loggers to obtain the first records of up to 7h long dives of a loggerhead turtle (Caretta caretta) overwintering in Greek waters. These represent the longest dives ever reported for a diving Marine Vertebrate. There is strong evidence that the dives were aerobic, because the turtle surfaced only for short intervals and before the calculated oxygen stores were depleted. This evidence suggests that the common belief that sea turtles hibernate underwater, as some freshwater turtles do, is incorrect.
Peggy Vincent - One of the best experts on this subject based on the ideXlab platform.
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virtual reexamination of a plesiosaurian specimen reptilia plesiosauria from the late cretaceous turonian of goulmima morocco using computed tomography
Journal of Vertebrate Paleontology, 2017Co-Authors: Remi Allemand, Nathalie Bardet, Alexandra Houssaye, Peggy VincentAbstract:ABSTRACT Turonian deposits of the Goulmima area, Er-Rachidia Province in southern Morocco, have yielded a diverse Marine Vertebrate fauna, including chondrichthyans, bony fishes, and large Marine reptiles such as plesiosaurians, mosasauroids, and turtles. These fossils are included in ovoid calcareous nodules that are difficult to prepare. Moreover, bones may be partially or totally dissolved, making their study difficult. Using computed tomography, we have reconstructed the entire skull anatomy of SMNS 81783, one of the rare plesiosaurian specimens found in this locality and more generally in Africa. The digital three-dimensional reconstruction of the skull and the mandible offers for the first time the possibility to describe this specimen exhaustively. The new anatomical characters recorded confirm that SMNS 81783 belongs to Elasmosauridae on the basis of (1) slender and triangular skull; (2) beak index equal to 42%; (3) temporal fossa estimated to occupy about 40% of the skull length; (4) long process...
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virtual reexamination of a plesiosaurian specimen reptilia plesiosauria from the late cretaceous turonian of goulmima morocco using computed tomography
Journal of Vertebrate Paleontology, 2017Co-Authors: Remi Allemand, Nathalie Bardet, Alexandra Houssaye, Peggy VincentAbstract:Turonian deposits of the Goulmima area, Er-Rachidia Province in southern Morocco, have yielded a diverse Marine Vertebrate fauna, including chondrichthyans, bony fishes, and large Marine reptiles such as plesiosaurians, mosasauroids, and turtles. These fossils are included in ovoid calcareous nodules that are difficult to prepare. Moreover, bones may be partially or totally dissolved, making their study difficult. Using computed tomography, we have reconstructed the entire skull anatomy of SMNS 81783, one of the rare plesiosaurian specimens found in this locality and more generally in Africa. The digital three-dimensional reconstruction of the skull and the mandible offers for the first time the possibility to describe this specimen exhaustively. The new anatomical characters recorded confirm that SMNS 81783 belongs to Elasmosauridae on the basis of (1) slender and triangular skull; (2) beak index equal to 42%; (3) temporal fossa estimated to occupy about 40% of the skull length; (4) long process of the premaxillae extending posteriorly to meet the parietal above the orbit and separating the frontals; and (5) margin of the temporal fenestra lacking obvious contribution from the frontal. A preliminary phylogenetic analysis confirms its elasmosaurid affinity. The relationships between SMNS 81783, Libonectes atlasense, and Libonectes morgani, as well as the presence of stapes and pineal foramen, are discussed.
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Marine Vertebrate remains from the Toarcian-Aalenian succession of southern Beaujolais, Rhone, France
Geological Magazine, 2013Co-Authors: Peggy Vincent, Jeremy E. Martin, Baptiste Suchéras-marx, Alex Léna, Kévin Janneau, Bruno Rousselle, Guillaume Suan, Bouziane Khalloufi, Valentin Fischer, Louis RulleauAbstract:A previously undocumented Marine Vertebrate fauna comprising ichthyosaur, plesiosaur, Marine crocodilian and fish remains from the Toarcian-Aalenian succession at Lafarge quarry, southern Beaujolais (Rhone, 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.
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zarafasaura oceanis a new elasmosaurid reptilia sauropterygia from the maastrichtian phosphates of morocco and the palaeobiogeography of latest cretaceous plesiosaurs
Gondwana Research, 2011Co-Authors: Peggy Vincent, Nathalie Bardet, X. Pereda Suberbiola, Baâdi Bouya, Mbarek Amaghzaz, Said MeslouhAbstract:Abstract Though the Maastrichtian Phosphates of Morocco have yielded very rich Marine Vertebrate assemblages, plesiosaurs remain very scarce in these strata. The only hitherto recognized taxon was Plesiosaurus mauritanicus Arambourg, 1952 , regarded here as a nomem dubium . Here we describe a new genus and species of elasmosaurid plesiosaur, Zarafasaura oceanis , which represents the first valid elasmosaurid plesiosaur described from the latest Cretaceous of Africa, and the second one from this continent. A phylogenetic analysis of plesiosauroids indicates that Zarafasaura oceanis has close affinities with elasmosaurids from the Late Cretaceous of North America and Japan. Among its distinctive suite of characters, the general shape and organisation of its squamosal and palate are unique among elasmosaurids. This new taxon completes our understanding of Late Cretaceous plesiosaur palaeobiodiversity and palaeobiogeography, and shows that Maastrichtian plesiosaurs were characterized by a quite high degree of endemism. They were also highly diversified and distributed worldwide, which supports the hypothesis of a catastrophic extinction of plesiosaurs at the K/T boundary.
Robert W Boessenecker - One of the best experts on this subject based on the ideXlab platform.
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The Early Pliocene extinction of the mega-toothed shark Otodus megalodon: a view from the eastern North Pacific
PeerJ Inc., 2019Co-Authors: Robert W Boessenecker, Dana J. Ehret, Douglas J. Long, Morgan Churchill, Evan Martin, Sarah J. BoesseneckerAbstract:The extinct giant shark Otodus megalodon is the last member of the predatory megatoothed lineage and is reported from Neogene sediments from nearly all continents. The timing of the extinction of Otodus megalodon is thought to be Pliocene, although reports of Pleistocene teeth fuel speculation that Otodus megalodon may still be extant. The longevity of the Otodus lineage (Paleocene to Pliocene) and its conspicuous absence in the modern fauna begs the question: when and why did this giant shark become extinct? Addressing this question requires a densely sampled Marine Vertebrate fossil record in concert with a robust geochronologic framework. Many historically important basins with stacked Otodus-bearing Neogene Marine Vertebrate fossil assemblages lack well-sampled and well-dated lower and upper Pliocene strata (e.g., Atlantic Coastal Plain). The fossil record of California, USA, and Baja California, Mexico, provides such an ideal sequence of assemblages preserved within well-dated lithostratigraphic sequences. This study reviews all records of Otodus megalodon from post-Messinian Marine strata from western North America and evaluates their reliability. All post-Zanclean Otodus megalodon occurrences from the eastern North Pacific exhibit clear evidence of reworking or lack reliable provenance; the youngest reliable records of Otodus megalodon are early Pliocene, suggesting an extinction at the early-late Pliocene boundary (∼3.6 Ma), corresponding with youngest occurrences of Otodus megalodon in Japan, the North Atlantic, and Mediterranean. This study also reevaluates a published dataset, thoroughly vetting each occurrence and justifying the geochronologic age of each, as well as excluding several dubious records. Reanalysis of the dataset using optimal linear estimation resulted in a median extinction date of 3.51 Ma, somewhat older than a previously proposed Pliocene-Pleistocene extinction date (2.6 Ma). Post-middle Miocene oceanographic changes and cooling sea surface temperature may have resulted in range fragmentation, while alongside competition with the newly evolved great white shark (Carcharodon carcharias) during the Pliocene may have led to the demise of the megatoothed shark. Alternatively, these findings may also suggest a globally asynchronous extinction of Otodus megalodon
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the oldest Marine Vertebrate fossil from the volcanic island of iceland a partial right whale skull from the high latitude pliocene tjornes formation
Palaeontology, 2017Co-Authors: Daniel J Field, Robert W Boessenecker, Rachel A Racicot, Lovisa Asbjornsdottir, Kristjan Jonasson, Allison Y Hsiang, Adam D Behlke, Jakob VintherAbstract:Extant baleen whales (Cetacea, Mysticeti) are a disparate and species-rich group, but little is known about their fossil record in the northernmost Atlantic Ocean, a region that supports considerable extant cetacean diversity. Iceland's geographical setting, dividing North Atlantic and Arctic waters, renders it ideally situated to shed light on cetacean evolution in this region. However, as a volcanic island, Iceland exhibits very little Marine sedimentary exposure, and fossil whales from Iceland older than the late Pleistocene are virtually unknown. Here, we present the first fossil whale found in situ from the Pliocene Tjornes Formation (c. 4.5 Ma), Iceland's only substantial Marine sedimentary outcrop. The specimen is diagnosed as a partial skull from a large right whale (Mysticeti, Balaenidae). This discovery highlights the Tjornes Formation as a potentially productive fossil Vertebrate locality. Additionally, this find indicates that right whales (Eubalaena) and bowhead whales (Balaena) were sympatric, with broadly overlapping latitudinal ranges in the Pliocene, in contrast to the modern latitudinal separation of their living counterparts.
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trace fossil evidence of predation upon bone eating worms on a baleen whale skeleton from the oligocene of new zealand
Lethaia, 2015Co-Authors: Robert W Boessenecker, Ewan R FordyceAbstract:The osteophagous worm Osedax (Annelida: Siboglinidae) colonizes Vertebrate bones in deep-sea environments globally. Osedax bioerosion of modern bones suggests a potentially destructive agent in the Marine Vertebrate fossil record, but the dearth of published reports of abundant Osedax traces suggests an uncertain taphonomic influence of this organism. This study reports Osedax traces (Osspecus boreholes, pockmarks and collapsed galleries) in an Oligocene baleen whale (Cetacea: Eomysticetidae) from New Zealand, which constitute the first record of fossil Osedax traces from the southern hemisphere. Some Osedax traces are cross-cut by linear biogenic scrape marks, implying that sharks or bony fish fed upon Osedax worms, a process which compounds or potentially accelerates worm-inflicted damage to Vertebrate bones in Marine environments.
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comparative taphonomy taphofacies and bonebeds of the mio pliocene purisima formation central california strong physical control on Marine Vertebrate preservation in shallow Marine settings
PLOS ONE, 2014Co-Authors: Robert W Boessenecker, Frank A. Perry, James G. SchmittAbstract:Background Taphonomic study of Marine Vertebrate remains has traditionally focused on single skeletons, lagerstatten, or bonebed genesis with few attempts to document environmental gradients in preservation. As such, establishment of a concrete taphonomic model for shallow Marine Vertebrate assemblages is lacking. The Neogene Purisima Formation of Northern California, a richly fossiliferous unit recording nearshore to offshore depositional settings, offers a unique opportunity to examine preservational trends across these settings. Methodology/Principal Findings Lithofacies analysis was conducted to place Vertebrate fossils within a hydrodynamic and depositional environmental context. Taphonomic data including abrasion, fragmentation, phosphatization, articulation, polish, and biogenic bone modification were recorded for over 1000 Vertebrate fossils of sharks, bony fish, birds, pinnipeds, odontocetes, mysticetes, sirenians, and land mammals. These data were used to compare both preservation of multiple taxa within a single lithofacies and preservation of individual taxa across lithofacies to document environmental gradients in preservation. Differential preservation between taxa indicates strong preservational bias within the Purisima Formation. Varying levels of abrasion, fragmentation, phosphatization, and articulation are strongly correlative with physical processes of sediment transport and sedimentation rate. Preservational characteristics were used to delineate four taphofacies corresponding to inner, middle, and outer shelf settings, and bonebeds. Application of sequence stratigraphic methods shows that bonebeds mark major stratigraphic discontinuities, while packages of rock between discontinuities consistently exhibit onshore-offshore changes in taphofacies. Conclusions/Significance Changes in Vertebrate preservation and bonebed character between lithofacies closely correspond to onshore-offshore changes in depositional setting, indicating that the dominant control of preservation is exerted by physical processes. The strong physical control on Marine Vertebrate preservation and preservational bias within the Purisima Formation has implications for paleoecologic and paleobiologic studies of Marine Vertebrates. Evidence of preservational bias among Marine Vertebrates suggests that careful consideration of taphonomic overprint must be undertaken before meaningful paleoecologic interpretations of shallow Marine Vertebrates is attempted.
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Histograms showing frequency of bone modifications (displayed as percentage of sample) in different Marine Vertebrate taxa.
2014Co-Authors: Robert W Boessenecker, Frank A. Perry, James G. SchmittAbstract:(A) abrasion, (B) fragmentation, and (C) polish. Abbreviations: A, Aves; C, Chondrichthyes; I.M., indeterminate mammal; M, Mysticeti; Od, Odontoceti; Os, Osteichthyes; P, Pinnipedia; S, Sirenia.
David W Sims - One of the best experts on this subject based on the ideXlab platform.
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review on the front line frontal zones as priority at sea conservation areas for mobile Marine Vertebrates
Journal of Applied Ecology, 2014Co-Authors: Kylie L Scales, David W Sims, Peter I Miller, Lucy A Hawkes, Simon N Ingram, Stephen C VotierAbstract:Summary 1. Identifying priority areas for Marine Vertebrate conservation is complex because species of conservation concern are highly mobile, inhabit dynamic habitats and are difficult to monitor. 2. Many Marine Vertebrates are known to associate with oceanographic fronts – physical interfaces at the transition between water masses – for foraging and migration, making them important candidate sites for conservation. Here, we review associations between Marine Vertebrates and fronts and how they vary with scale, regional oceanography and foraging ecology. 3. Accessibility, spatiotemporal predictability and relative productivity of front-associated foraging habitats are key aspects of their ecological importance. Predictable mesoscale (10s– 100s km) regions of persistent frontal activity (‘frontal zones’) are particularly significant. 4. Frontal zones are hotspots of overlap between critical habitat and spatially explicit anthropogenic threats, such as the concentration of fisheries activity. As such, they represent tractable conservation units, in which to target measures for threat mitigation. 5. Front mapping via Earth observation (EO) remote sensing facilitates identification and monitoring of these hotspots of vulnerability. Seasonal or climatological products can locate biophysical hotspots, while near-real-time front mapping augments the suite of tools supporting spatially dynamic ocean management. 6. Synthesis and applications. Frontal zones are ecologically important for mobile Marine Vertebrates. We surmise that relative accessibility, predictability and productivity are key biophysical characteristics of ecologically significant frontal zones in contrasting oceanographic regions. Persistent frontal zones are potential priority conservation areas for multiple Marine Vertebrate taxa and are easily identifiable through front mapping via EO remote sensing. These insights are useful for Marine spatial planning and Marine biodiversity conservation, both within Exclusive Economic Zones and in the open oceans.
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molecular markers reveal spatially segregated cryptic species in a critically endangered fish the common skate dipturus batis
Proceedings of The Royal Society B: Biological Sciences, 2010Co-Authors: Andrew M Griffiths, David W Sims, Stephen P Cotterell, Aliya El Nagar, Jim R Ellis, Arve Lynghammar, Matthew Mchugh, Francis Neat, Nicolas G Pade, Nuno QueirozAbstract:Many sharks and skates are particularly vulnerable to overfishing because of their large size, slow growth, late maturity and low fecundity. In Europe dramatic population declines have taken place in common skate (Dipturus batis L.), one of the largest demersal fish in regional shelf seas, leading to extirpations from substantial parts of its former range. Here we report the discovery of cryptic species in common skate collected from the northeast Atlantic continental shelf. Data from nuclear microsatellite markers indicated two clearly distinct clades and phylogenetic analysis of mitochondrial DNA sequences demonstrated monophyly of each one of them. Capture locations showed evidence of strong spatial segregation, with one taxon occurring mainly in waters off the southern British Isles and around Rockall, while the other was restricted to more northerly shelf waters. These apparently cryptic species showed overlapping substrate and depth preferences, but distributional limits were closely related to temperature gradients, potentially indicating thermal limits to their distributions. This discovery of hidden diversity within a large, critically endangered Marine Vertebrate demonstrates how Marine biodiversity can be underestimated, even in such a relatively well-studied and heavily exploited region.
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sexual segregation in Marine fish reptiles birds and mammals behaviour patterns mechanisms and conservation implications
Advances in Marine Biology, 2008Co-Authors: Victoria J Wearmouth, David W SimsAbstract:Abstract Sexual segregation occurs when members of a species separate such that the sexes live apart, either singly or in single‐sex groups. It can be broadly categorised into two types: habitat segregation and social segregation. Sexual segregation is a behavioural phenomenon that is widespread in the animal kingdom yet the underlying causes remain poorly understood. Sexual segregation has been widely studied among terrestrial mammals such as ungulates, but it has been less well documented in the Marine environment. This chapter clarifies terms and concepts which have emerged from the investigation of sexual segregation in terrestrial ecology and examines how a similar methodological approach may be complicated by differences of Marine species. Here we discuss the behavioural patterns of sexual segregation among Marine fish, reptile, bird and mammal species. Five hypotheses have been forwarded to account for sexual segregation, largely emerging from investigation of sexual segregation in terrestrial ungulates: the predation risk, forage selection, activity budget, thermal niche–fecundity and social factors hypotheses. These mechanisms are reviewed following careful assessment of their applicability to Marine Vertebrate species and case studies of Marine Vertebrates which support each mechanism recounted. Rigorous testing of all hypotheses is lacking from both the terrestrial and Marine Vertebrate literature and those analyses which have been attempted are often confounded by factors such as sexual body‐size dimorphism. In this context, we indicate the value of studying model species which are monomorphic with respect to body size and discuss possible underlying causes for sexual segregation in this species. We also discuss why it is important to understand sexual segregation, for example, by illustrating how differential exploitation of the sexes by humans can lead to population decline.