Richard Cloutier

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Richard Cloutier

Richard Cloutier

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Biography

Universite du Quebec a Rimouski - Biology

professeur-chercheur chez Université du Québec à Rimouski
Higher Education
Richard
Cloutier
Rimouski, Quebec, Canada
Since 2000, I have integrated evolutionary developmental biology to my paleontological and systematic expertises. For the past 5 yrs, I have been working on a series of projects that could be divided into three major axes: (1) phenotypic plasticity, (2) evolutionary developmental patterns, and (3) paleobiology.

Experience

  • The Natural History Museum

    Postdoctoral Researcher

    Research in vertebrate paleontology and phylogenetic analysis

  • Université du Québec à Rimouski

    professeur-chercheur

    Teaching and research

  • United medical and dental school, Guy's Hospital

    Postdoctoral Fellow

    Research in paleohistology and image analysis

  • CNRS

    Chargé de recherche

    research in systematics, paleontology and paleoenvironment associated with major events in lower vertebrate evolution

Education

  • University of Kansas

    PhD

    Systematics & Ecology

  • University of Kansas

    Master of Philosophy (M.Phil.)

    Zoology/Animal Biology

  • Université de Montréal

    Master of Science (MSc)

    Biostatistics

Publications

  • Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

    Journal of Fish Biology

    An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

  • Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

    Journal of Fish Biology

    An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

  • Dynamic Skeletogenesis in Fishes: Insight of Exercise Training on Developmental Plasticity

    Developmental Dynamics

    Background: Through developmental and evolutionary time, organisms respond variably to their environment not only in terms of size and shape but also in term of timing. Developmental plasticity can potentially act on various aspects of the timing of developmental events. When dealing with the chondrification and ossification of the vertebrate skeleton, developmental properties include the onset, offset, duration of events, transitions of skeletal states, order of events in a sequence, and the trajectories of developmental events. We studied the phenotypic response of median fin endoskeleton in developing newly-hatched Arctic charr (Salvelinus alpinus) under differential water velocity. Results: Developmental progress of chondrification in all fins is less influenced than ossification by an increase of water velocity. The most responsive elements, meaning those elements with greater onset plasticity owing to a water velocity increase, differ in terms of early versus late developmental events. The most responsive elements are those that chondrify and to a greater extent ossify later in the development. Conclusions: Plasticity is documented for the timing of onset and the transition of skeletal states rather than the order of events within a sequence. Similarities of plastic response in developmental patterns could be used as a powerful criterion to strengthen the identification of phenotypic modules.

  • Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

    Journal of Fish Biology

    An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

  • Dynamic Skeletogenesis in Fishes: Insight of Exercise Training on Developmental Plasticity

    Developmental Dynamics

    Background: Through developmental and evolutionary time, organisms respond variably to their environment not only in terms of size and shape but also in term of timing. Developmental plasticity can potentially act on various aspects of the timing of developmental events. When dealing with the chondrification and ossification of the vertebrate skeleton, developmental properties include the onset, offset, duration of events, transitions of skeletal states, order of events in a sequence, and the trajectories of developmental events. We studied the phenotypic response of median fin endoskeleton in developing newly-hatched Arctic charr (Salvelinus alpinus) under differential water velocity. Results: Developmental progress of chondrification in all fins is less influenced than ossification by an increase of water velocity. The most responsive elements, meaning those elements with greater onset plasticity owing to a water velocity increase, differ in terms of early versus late developmental events. The most responsive elements are those that chondrify and to a greater extent ossify later in the development. Conclusions: Plasticity is documented for the timing of onset and the transition of skeletal states rather than the order of events within a sequence. Similarities of plastic response in developmental patterns could be used as a powerful criterion to strengthen the identification of phenotypic modules.

  • Elpistostege and the light and dark side of the moon: New data on the paleoenvironment of the fish-to-tetrapod transition

    Journal of Vertebrate Paleontology, Supplement

    Paleoenvironmental considerations of the fish-to-tetrapod transition have suggested that early tetrapods and their closest relatives, the elpistostegalian fishes, were exploiting a range of habitats. Three Middle-Late Devonian elpistostegalian taxa are most critical to understand this environmental-evolutionary transition. The late Givetian Panderichthys is associated with a deltaic environment, whereas the early-middle Frasnian Tiktaalik is associated with a non-marine depositional setting. The middle Frasnian Elpistostege watsoni is preserved in the renowned Escuminac Formation (Miguasha, Quebec, Canada), a siliciclastic formation interpreted as an estuarine environment. Based on sequential stratigraphy, the Escuminac Formation (119 m) was recently characterized by five transgressive/regressive sequences within an inner wave-dominated estuary showing shifts in continentalization. Furthermore, isotopic (Rb-Sr) analyses of bioapatites support a brackish to marine environment. All known Elpistostege material, including the very first complete specimen recently discovered, has been found in laminated horizons associated with transgressive or highstand components of the stratigraphic sequences. The new specimen has been found in association with the acanthodian Triazeugacanthus and Homalacanthus, the conchostracan Asmusia and the lignophyte Archaeopteris, in a horizon displaying a regular alternation of dark (clay and amorphous organic matter) and light (silt-size calcite and quartz) laminae forming couplets. Individual lamina thicknesses were measured on high resolution digital images of the enclosing bed in order to evaluate the pattern of thickness variation...

  • Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

    Journal of Fish Biology

    An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

  • Dynamic Skeletogenesis in Fishes: Insight of Exercise Training on Developmental Plasticity

    Developmental Dynamics

    Background: Through developmental and evolutionary time, organisms respond variably to their environment not only in terms of size and shape but also in term of timing. Developmental plasticity can potentially act on various aspects of the timing of developmental events. When dealing with the chondrification and ossification of the vertebrate skeleton, developmental properties include the onset, offset, duration of events, transitions of skeletal states, order of events in a sequence, and the trajectories of developmental events. We studied the phenotypic response of median fin endoskeleton in developing newly-hatched Arctic charr (Salvelinus alpinus) under differential water velocity. Results: Developmental progress of chondrification in all fins is less influenced than ossification by an increase of water velocity. The most responsive elements, meaning those elements with greater onset plasticity owing to a water velocity increase, differ in terms of early versus late developmental events. The most responsive elements are those that chondrify and to a greater extent ossify later in the development. Conclusions: Plasticity is documented for the timing of onset and the transition of skeletal states rather than the order of events within a sequence. Similarities of plastic response in developmental patterns could be used as a powerful criterion to strengthen the identification of phenotypic modules.

  • Elpistostege and the light and dark side of the moon: New data on the paleoenvironment of the fish-to-tetrapod transition

    Journal of Vertebrate Paleontology, Supplement

    Paleoenvironmental considerations of the fish-to-tetrapod transition have suggested that early tetrapods and their closest relatives, the elpistostegalian fishes, were exploiting a range of habitats. Three Middle-Late Devonian elpistostegalian taxa are most critical to understand this environmental-evolutionary transition. The late Givetian Panderichthys is associated with a deltaic environment, whereas the early-middle Frasnian Tiktaalik is associated with a non-marine depositional setting. The middle Frasnian Elpistostege watsoni is preserved in the renowned Escuminac Formation (Miguasha, Quebec, Canada), a siliciclastic formation interpreted as an estuarine environment. Based on sequential stratigraphy, the Escuminac Formation (119 m) was recently characterized by five transgressive/regressive sequences within an inner wave-dominated estuary showing shifts in continentalization. Furthermore, isotopic (Rb-Sr) analyses of bioapatites support a brackish to marine environment. All known Elpistostege material, including the very first complete specimen recently discovered, has been found in laminated horizons associated with transgressive or highstand components of the stratigraphic sequences. The new specimen has been found in association with the acanthodian Triazeugacanthus and Homalacanthus, the conchostracan Asmusia and the lignophyte Archaeopteris, in a horizon displaying a regular alternation of dark (clay and amorphous organic matter) and light (silt-size calcite and quartz) laminae forming couplets. Individual lamina thicknesses were measured on high resolution digital images of the enclosing bed in order to evaluate the pattern of thickness variation...

  • External morphology of the Devonian Placoderm Bothriolepis canadensis

    Journal of Vertebrate Paleontology, Supplement

    The external morphology of the well-known, middle Frasnian Bothriolepis canadensis from the Escuminac Formation (Miguasha, Canada) is revised using cutting- edge technology in three-dimensional (3D) digital imagery. Nineteen well-preserved and articulated specimens of B. canadensis were used to reconstruct a 3D digital model of the dermal armor (cephalic and thoracic parts covering 35.6% of the total length), whereas four specimens were used to reconstruct the posterior part of the body. The 3D model representing a large adult specimen (44 cm total length) allows us to investigate some biomechanical aspects and constraints. Mobility of the cephalic armor, submarginal plates (“opercular plates”) and pectoral fins has been previously hypothesized based on inaccurate reconstructions. In contrast to previous reconstructions, there is no indication of mobility between the cephalic and thoracic armors. The submarginal plate is fixed upon the cephalic armor; a gill opening is located between the submarginal plate and the anterior ventrolateral plate of the thoracic armor. The median dorsal ridge of the thoracic armor forms a hydrodynamic dorsal crest with its maximum height along the posterior median dorsal plate. In contrast to previous interpretations, the fully retracted and protracted (70o) position of the pectoral fin allows only for restricted movement. Maximum of mobility is reached in a protracted angle of 16o which allows a rotation of 30o around the brachial process and 20o in an up-and-down movement. The 3D model of B. canadensis brings out some unexpected novelties on a supposedly well-known Devonian fish.

  • Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

    Journal of Fish Biology

    An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

  • Dynamic Skeletogenesis in Fishes: Insight of Exercise Training on Developmental Plasticity

    Developmental Dynamics

    Background: Through developmental and evolutionary time, organisms respond variably to their environment not only in terms of size and shape but also in term of timing. Developmental plasticity can potentially act on various aspects of the timing of developmental events. When dealing with the chondrification and ossification of the vertebrate skeleton, developmental properties include the onset, offset, duration of events, transitions of skeletal states, order of events in a sequence, and the trajectories of developmental events. We studied the phenotypic response of median fin endoskeleton in developing newly-hatched Arctic charr (Salvelinus alpinus) under differential water velocity. Results: Developmental progress of chondrification in all fins is less influenced than ossification by an increase of water velocity. The most responsive elements, meaning those elements with greater onset plasticity owing to a water velocity increase, differ in terms of early versus late developmental events. The most responsive elements are those that chondrify and to a greater extent ossify later in the development. Conclusions: Plasticity is documented for the timing of onset and the transition of skeletal states rather than the order of events within a sequence. Similarities of plastic response in developmental patterns could be used as a powerful criterion to strengthen the identification of phenotypic modules.

  • Elpistostege and the light and dark side of the moon: New data on the paleoenvironment of the fish-to-tetrapod transition

    Journal of Vertebrate Paleontology, Supplement

    Paleoenvironmental considerations of the fish-to-tetrapod transition have suggested that early tetrapods and their closest relatives, the elpistostegalian fishes, were exploiting a range of habitats. Three Middle-Late Devonian elpistostegalian taxa are most critical to understand this environmental-evolutionary transition. The late Givetian Panderichthys is associated with a deltaic environment, whereas the early-middle Frasnian Tiktaalik is associated with a non-marine depositional setting. The middle Frasnian Elpistostege watsoni is preserved in the renowned Escuminac Formation (Miguasha, Quebec, Canada), a siliciclastic formation interpreted as an estuarine environment. Based on sequential stratigraphy, the Escuminac Formation (119 m) was recently characterized by five transgressive/regressive sequences within an inner wave-dominated estuary showing shifts in continentalization. Furthermore, isotopic (Rb-Sr) analyses of bioapatites support a brackish to marine environment. All known Elpistostege material, including the very first complete specimen recently discovered, has been found in laminated horizons associated with transgressive or highstand components of the stratigraphic sequences. The new specimen has been found in association with the acanthodian Triazeugacanthus and Homalacanthus, the conchostracan Asmusia and the lignophyte Archaeopteris, in a horizon displaying a regular alternation of dark (clay and amorphous organic matter) and light (silt-size calcite and quartz) laminae forming couplets. Individual lamina thicknesses were measured on high resolution digital images of the enclosing bed in order to evaluate the pattern of thickness variation...

  • External morphology of the Devonian Placoderm Bothriolepis canadensis

    Journal of Vertebrate Paleontology, Supplement

    The external morphology of the well-known, middle Frasnian Bothriolepis canadensis from the Escuminac Formation (Miguasha, Canada) is revised using cutting- edge technology in three-dimensional (3D) digital imagery. Nineteen well-preserved and articulated specimens of B. canadensis were used to reconstruct a 3D digital model of the dermal armor (cephalic and thoracic parts covering 35.6% of the total length), whereas four specimens were used to reconstruct the posterior part of the body. The 3D model representing a large adult specimen (44 cm total length) allows us to investigate some biomechanical aspects and constraints. Mobility of the cephalic armor, submarginal plates (“opercular plates”) and pectoral fins has been previously hypothesized based on inaccurate reconstructions. In contrast to previous reconstructions, there is no indication of mobility between the cephalic and thoracic armors. The submarginal plate is fixed upon the cephalic armor; a gill opening is located between the submarginal plate and the anterior ventrolateral plate of the thoracic armor. The median dorsal ridge of the thoracic armor forms a hydrodynamic dorsal crest with its maximum height along the posterior median dorsal plate. In contrast to previous interpretations, the fully retracted and protracted (70o) position of the pectoral fin allows only for restricted movement. Maximum of mobility is reached in a protracted angle of 16o which allows a rotation of 30o around the brachial process and 20o in an up-and-down movement. The 3D model of B. canadensis brings out some unexpected novelties on a supposedly well-known Devonian fish.

  • New methodology for 3D reconstruction of fossil fish using digital imagery

    Journal of Vertebrate Paleontology, Supplement

    Non-invasive technologies, such as CT-scan, traditional and synchrotron-based micro-CT-scan, are gaining in popularity for quantitative visualization of fossilized anatomical structures and ultrastructures. However, most studies in virtual paleontology are performed on a limited number of specimens owing to the cost of utilisation and the time required for image acquisition, processing, and interpretation. Usage of such technologies can also be limited by the taphonomic condition and size of the fossils, as well as the type of matrix surrounding the specimens. However, three-dimensional reconstruction (3D) of taxon does not necessarily require histological and ultrastructural investigation. Non-invasive 3D laser surface scanner provides the possibility to acquire high-definition surface-scanned images of prepared specimens without the potential limitations imposed by other technologies. Results are rapid and easy to use for research purpose and collection management. A new and precise method to 3D-reconstruct fossilized taxon was developed using a 3D laser surface scanner combined with cutting- edge digital imagery tools. Nineteen well-preserved and articulated specimens of the Late Devonian placoderm Bothriolepis canadensis (Miguasha, eastern Canada) were scanned at maximum resolution. Digital data were cleaned in an acquisition and processing software. Using a digital sculpting software, superposition of multiple 3D meshed models allows for size and shape corrections and taphonomical corrections providing an unbiased and accurate reconstruction of B. canadensis. This new digital reconstruction highlights previous anatomical misinterpretations on the morphology, size and shape, and articulation of this placoderm; most of the modifications would not have been possible without the usage of the digital 3D model.

  • Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

    Journal of Fish Biology

    An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

  • Dynamic Skeletogenesis in Fishes: Insight of Exercise Training on Developmental Plasticity

    Developmental Dynamics

    Background: Through developmental and evolutionary time, organisms respond variably to their environment not only in terms of size and shape but also in term of timing. Developmental plasticity can potentially act on various aspects of the timing of developmental events. When dealing with the chondrification and ossification of the vertebrate skeleton, developmental properties include the onset, offset, duration of events, transitions of skeletal states, order of events in a sequence, and the trajectories of developmental events. We studied the phenotypic response of median fin endoskeleton in developing newly-hatched Arctic charr (Salvelinus alpinus) under differential water velocity. Results: Developmental progress of chondrification in all fins is less influenced than ossification by an increase of water velocity. The most responsive elements, meaning those elements with greater onset plasticity owing to a water velocity increase, differ in terms of early versus late developmental events. The most responsive elements are those that chondrify and to a greater extent ossify later in the development. Conclusions: Plasticity is documented for the timing of onset and the transition of skeletal states rather than the order of events within a sequence. Similarities of plastic response in developmental patterns could be used as a powerful criterion to strengthen the identification of phenotypic modules.

  • Elpistostege and the light and dark side of the moon: New data on the paleoenvironment of the fish-to-tetrapod transition

    Journal of Vertebrate Paleontology, Supplement

    Paleoenvironmental considerations of the fish-to-tetrapod transition have suggested that early tetrapods and their closest relatives, the elpistostegalian fishes, were exploiting a range of habitats. Three Middle-Late Devonian elpistostegalian taxa are most critical to understand this environmental-evolutionary transition. The late Givetian Panderichthys is associated with a deltaic environment, whereas the early-middle Frasnian Tiktaalik is associated with a non-marine depositional setting. The middle Frasnian Elpistostege watsoni is preserved in the renowned Escuminac Formation (Miguasha, Quebec, Canada), a siliciclastic formation interpreted as an estuarine environment. Based on sequential stratigraphy, the Escuminac Formation (119 m) was recently characterized by five transgressive/regressive sequences within an inner wave-dominated estuary showing shifts in continentalization. Furthermore, isotopic (Rb-Sr) analyses of bioapatites support a brackish to marine environment. All known Elpistostege material, including the very first complete specimen recently discovered, has been found in laminated horizons associated with transgressive or highstand components of the stratigraphic sequences. The new specimen has been found in association with the acanthodian Triazeugacanthus and Homalacanthus, the conchostracan Asmusia and the lignophyte Archaeopteris, in a horizon displaying a regular alternation of dark (clay and amorphous organic matter) and light (silt-size calcite and quartz) laminae forming couplets. Individual lamina thicknesses were measured on high resolution digital images of the enclosing bed in order to evaluate the pattern of thickness variation...

  • External morphology of the Devonian Placoderm Bothriolepis canadensis

    Journal of Vertebrate Paleontology, Supplement

    The external morphology of the well-known, middle Frasnian Bothriolepis canadensis from the Escuminac Formation (Miguasha, Canada) is revised using cutting- edge technology in three-dimensional (3D) digital imagery. Nineteen well-preserved and articulated specimens of B. canadensis were used to reconstruct a 3D digital model of the dermal armor (cephalic and thoracic parts covering 35.6% of the total length), whereas four specimens were used to reconstruct the posterior part of the body. The 3D model representing a large adult specimen (44 cm total length) allows us to investigate some biomechanical aspects and constraints. Mobility of the cephalic armor, submarginal plates (“opercular plates”) and pectoral fins has been previously hypothesized based on inaccurate reconstructions. In contrast to previous reconstructions, there is no indication of mobility between the cephalic and thoracic armors. The submarginal plate is fixed upon the cephalic armor; a gill opening is located between the submarginal plate and the anterior ventrolateral plate of the thoracic armor. The median dorsal ridge of the thoracic armor forms a hydrodynamic dorsal crest with its maximum height along the posterior median dorsal plate. In contrast to previous interpretations, the fully retracted and protracted (70o) position of the pectoral fin allows only for restricted movement. Maximum of mobility is reached in a protracted angle of 16o which allows a rotation of 30o around the brachial process and 20o in an up-and-down movement. The 3D model of B. canadensis brings out some unexpected novelties on a supposedly well-known Devonian fish.

  • New methodology for 3D reconstruction of fossil fish using digital imagery

    Journal of Vertebrate Paleontology, Supplement

    Non-invasive technologies, such as CT-scan, traditional and synchrotron-based micro-CT-scan, are gaining in popularity for quantitative visualization of fossilized anatomical structures and ultrastructures. However, most studies in virtual paleontology are performed on a limited number of specimens owing to the cost of utilisation and the time required for image acquisition, processing, and interpretation. Usage of such technologies can also be limited by the taphonomic condition and size of the fossils, as well as the type of matrix surrounding the specimens. However, three-dimensional reconstruction (3D) of taxon does not necessarily require histological and ultrastructural investigation. Non-invasive 3D laser surface scanner provides the possibility to acquire high-definition surface-scanned images of prepared specimens without the potential limitations imposed by other technologies. Results are rapid and easy to use for research purpose and collection management. A new and precise method to 3D-reconstruct fossilized taxon was developed using a 3D laser surface scanner combined with cutting- edge digital imagery tools. Nineteen well-preserved and articulated specimens of the Late Devonian placoderm Bothriolepis canadensis (Miguasha, eastern Canada) were scanned at maximum resolution. Digital data were cleaned in an acquisition and processing software. Using a digital sculpting software, superposition of multiple 3D meshed models allows for size and shape corrections and taphonomical corrections providing an unbiased and accurate reconstruction of B. canadensis. This new digital reconstruction highlights previous anatomical misinterpretations on the morphology, size and shape, and articulation of this placoderm; most of the modifications would not have been possible without the usage of the digital 3D model.

  • Great Canadian Lagerstätten 4. The Devonian Miguasha biota (Quebec): an UNESCO World Heritage, a time capsule in the early history of vertebrates

    Geoscience Canada

    Over the past 170 years, the Late Devonian Miguasha biota from eastern Canada has yielded a diverse aquatic assemblage including 20 species of lower vertebrates (anaspids, osteostracans, placoderms, acanthodians, actinopterygians and sarcopterygians), a more limited invertebrate assemblage, and a continental component including plants, scorpions and millipedes. Originally interpreted as a freshwater lacustrine environment, recent paleontological, taphonomic, sedimentological and geochemical evidence corroborates a brackish estuarine setting. Over 18,000 fish specimens have been recovered showing various modes of fossilization, including uncompressed material and soft-tissue preservation. Most vertebrates are known from numerous, complete, articulated specimens. Exceptionally well-preserved larval and juvenile specimens have been identified for 14 out of the 20 species of fishes, allowing growth studies. Numerous horizons within the Escuminac Formation are now interpreted as either Konservat– or Konzentrat–Lagerstätten.

  • Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

    Journal of Fish Biology

    An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

  • Dynamic Skeletogenesis in Fishes: Insight of Exercise Training on Developmental Plasticity

    Developmental Dynamics

    Background: Through developmental and evolutionary time, organisms respond variably to their environment not only in terms of size and shape but also in term of timing. Developmental plasticity can potentially act on various aspects of the timing of developmental events. When dealing with the chondrification and ossification of the vertebrate skeleton, developmental properties include the onset, offset, duration of events, transitions of skeletal states, order of events in a sequence, and the trajectories of developmental events. We studied the phenotypic response of median fin endoskeleton in developing newly-hatched Arctic charr (Salvelinus alpinus) under differential water velocity. Results: Developmental progress of chondrification in all fins is less influenced than ossification by an increase of water velocity. The most responsive elements, meaning those elements with greater onset plasticity owing to a water velocity increase, differ in terms of early versus late developmental events. The most responsive elements are those that chondrify and to a greater extent ossify later in the development. Conclusions: Plasticity is documented for the timing of onset and the transition of skeletal states rather than the order of events within a sequence. Similarities of plastic response in developmental patterns could be used as a powerful criterion to strengthen the identification of phenotypic modules.

  • Elpistostege and the light and dark side of the moon: New data on the paleoenvironment of the fish-to-tetrapod transition

    Journal of Vertebrate Paleontology, Supplement

    Paleoenvironmental considerations of the fish-to-tetrapod transition have suggested that early tetrapods and their closest relatives, the elpistostegalian fishes, were exploiting a range of habitats. Three Middle-Late Devonian elpistostegalian taxa are most critical to understand this environmental-evolutionary transition. The late Givetian Panderichthys is associated with a deltaic environment, whereas the early-middle Frasnian Tiktaalik is associated with a non-marine depositional setting. The middle Frasnian Elpistostege watsoni is preserved in the renowned Escuminac Formation (Miguasha, Quebec, Canada), a siliciclastic formation interpreted as an estuarine environment. Based on sequential stratigraphy, the Escuminac Formation (119 m) was recently characterized by five transgressive/regressive sequences within an inner wave-dominated estuary showing shifts in continentalization. Furthermore, isotopic (Rb-Sr) analyses of bioapatites support a brackish to marine environment. All known Elpistostege material, including the very first complete specimen recently discovered, has been found in laminated horizons associated with transgressive or highstand components of the stratigraphic sequences. The new specimen has been found in association with the acanthodian Triazeugacanthus and Homalacanthus, the conchostracan Asmusia and the lignophyte Archaeopteris, in a horizon displaying a regular alternation of dark (clay and amorphous organic matter) and light (silt-size calcite and quartz) laminae forming couplets. Individual lamina thicknesses were measured on high resolution digital images of the enclosing bed in order to evaluate the pattern of thickness variation...

  • External morphology of the Devonian Placoderm Bothriolepis canadensis

    Journal of Vertebrate Paleontology, Supplement

    The external morphology of the well-known, middle Frasnian Bothriolepis canadensis from the Escuminac Formation (Miguasha, Canada) is revised using cutting- edge technology in three-dimensional (3D) digital imagery. Nineteen well-preserved and articulated specimens of B. canadensis were used to reconstruct a 3D digital model of the dermal armor (cephalic and thoracic parts covering 35.6% of the total length), whereas four specimens were used to reconstruct the posterior part of the body. The 3D model representing a large adult specimen (44 cm total length) allows us to investigate some biomechanical aspects and constraints. Mobility of the cephalic armor, submarginal plates (“opercular plates”) and pectoral fins has been previously hypothesized based on inaccurate reconstructions. In contrast to previous reconstructions, there is no indication of mobility between the cephalic and thoracic armors. The submarginal plate is fixed upon the cephalic armor; a gill opening is located between the submarginal plate and the anterior ventrolateral plate of the thoracic armor. The median dorsal ridge of the thoracic armor forms a hydrodynamic dorsal crest with its maximum height along the posterior median dorsal plate. In contrast to previous interpretations, the fully retracted and protracted (70o) position of the pectoral fin allows only for restricted movement. Maximum of mobility is reached in a protracted angle of 16o which allows a rotation of 30o around the brachial process and 20o in an up-and-down movement. The 3D model of B. canadensis brings out some unexpected novelties on a supposedly well-known Devonian fish.

  • New methodology for 3D reconstruction of fossil fish using digital imagery

    Journal of Vertebrate Paleontology, Supplement

    Non-invasive technologies, such as CT-scan, traditional and synchrotron-based micro-CT-scan, are gaining in popularity for quantitative visualization of fossilized anatomical structures and ultrastructures. However, most studies in virtual paleontology are performed on a limited number of specimens owing to the cost of utilisation and the time required for image acquisition, processing, and interpretation. Usage of such technologies can also be limited by the taphonomic condition and size of the fossils, as well as the type of matrix surrounding the specimens. However, three-dimensional reconstruction (3D) of taxon does not necessarily require histological and ultrastructural investigation. Non-invasive 3D laser surface scanner provides the possibility to acquire high-definition surface-scanned images of prepared specimens without the potential limitations imposed by other technologies. Results are rapid and easy to use for research purpose and collection management. A new and precise method to 3D-reconstruct fossilized taxon was developed using a 3D laser surface scanner combined with cutting- edge digital imagery tools. Nineteen well-preserved and articulated specimens of the Late Devonian placoderm Bothriolepis canadensis (Miguasha, eastern Canada) were scanned at maximum resolution. Digital data were cleaned in an acquisition and processing software. Using a digital sculpting software, superposition of multiple 3D meshed models allows for size and shape corrections and taphonomical corrections providing an unbiased and accurate reconstruction of B. canadensis. This new digital reconstruction highlights previous anatomical misinterpretations on the morphology, size and shape, and articulation of this placoderm; most of the modifications would not have been possible without the usage of the digital 3D model.

  • Great Canadian Lagerstätten 4. The Devonian Miguasha biota (Quebec): an UNESCO World Heritage, a time capsule in the early history of vertebrates

    Geoscience Canada

    Over the past 170 years, the Late Devonian Miguasha biota from eastern Canada has yielded a diverse aquatic assemblage including 20 species of lower vertebrates (anaspids, osteostracans, placoderms, acanthodians, actinopterygians and sarcopterygians), a more limited invertebrate assemblage, and a continental component including plants, scorpions and millipedes. Originally interpreted as a freshwater lacustrine environment, recent paleontological, taphonomic, sedimentological and geochemical evidence corroborates a brackish estuarine setting. Over 18,000 fish specimens have been recovered showing various modes of fossilization, including uncompressed material and soft-tissue preservation. Most vertebrates are known from numerous, complete, articulated specimens. Exceptionally well-preserved larval and juvenile specimens have been identified for 14 out of the 20 species of fishes, allowing growth studies. Numerous horizons within the Escuminac Formation are now interpreted as either Konservat– or Konzentrat–Lagerstätten.

  • A new piece of the Devonian fish-to-tetrapod puzzle: The discovery of a complete specimen of Elpistostege

    Journal of vertebrate paleontology

    Recent hypotheses on the origin of tetrapods rely heavily on the anatomy of only a few tetrapod-like fossils from the Middle-Upper Devonian. These tetrapod-like taxa, referred to as elpistostegalians, constitute a paraphyletic group including Panderichthys rhombolepis from the late Givetian of Latvia, Elpistostege watsoni from the middle Frasnian of Quebec, and Tiktaalik roseae from the early-middle Frasnian of Arctic Canada. Although of uncertain phylogenetic position, Gogonasus andrewsaea from the early Frasnian of Western Australia and Livoniana multidentata from the late Givetian of Latvia and Estonia have also been suggested to be closely related to elpistostegalians. With the exception of Livoniana (fragments of lower jaw) and Elpistostege (two partial skulls and a small trunk segment), the anatomy of Panderichthys and Tiktaalik is fairly well documented. The recent discovery of a 1.56 m-long, completely articulated specimen of Elpistostege watsoni from the Escuminac Formation (Miguasha) is filling out a major gap of anatomical information with respect to the fish-to-tetrapod transition. Elpistostege has elongated trunk and caudal regions with oversized pectoral fins. A high- energy CT-scan investigation of the complete specimen reveals internal cranial and paired fin anatomy. This makes it the most complete elpistostegalian known allowing us to reinvestigate its phylogenetic position. Elpistostege is unambiguously more closely related to Tiktaalik and early tetrapods than to Panderichthys.

  • A new piece of the Devonian fish-to-tetrapod puzzle: The discovery of a complete specimen of Elpistostege

    Journal of Vertebrate Paleontology, Supplement

    Recent hypotheses on the origin of tetrapods rely heavily on the anatomy of only a few tetrapod-like fossils from the Middle-Upper Devonian. These tetrapod-like taxa, referred to as elpistostegalians, constitute a paraphyletic group including Panderichthys rhombolepis from the late Givetian of Latvia, Elpistostege watsoni from the middle Frasnian of Quebec, and Tiktaalik roseae from the early-middle Frasnian of Arctic Canada. Although of uncertain phylogenetic position, Gogonasus andrewsaea from the early Frasnian of Western Australia and Livoniana multidentata from the late Givetian of Latvia and Estonia have also been suggested to be closely related to elpistostegalians. With the exception of Livoniana (fragments of lower jaw) and Elpistostege (two partial skulls and a small trunk segment), the anatomy of Panderichthys and Tiktaalik is fairly well documented. The recent discovery of a 1.56 m-long, completely articulated specimen of Elpistostege watsoni from the Escuminac Formation (Miguasha) is filling out a major gap of anatomical information with respect to the fish-to-tetrapod transition. Elpistostege has elongated trunk and caudal regions with oversized pectoral fins. A high- energy CT-scan investigation of the complete specimen reveals internal cranial and paired fin anatomy. This makes it the most complete elpistostegalian known allowing us to reinvestigate its phylogenetic position. Elpistostege is unambiguously more closely related to Tiktaalik and early tetrapods than to Panderichthys.

  • Early ontogeny of the Atlantic halibut Hippoglossus hippoglossus head

    Journal of Fish Biology

    An ontogenetic sequence of Atlantic halibut Hippoglossus hippoglossus larvae, reared in intensive culture conditions, was cleared and stained and histologically processed to determine normal cranial chondrification for specimens ranging from 0 to 41 days post-hatch (dph). Twenty-six cranial cartilaginous structures were described, at daily intervals post-hatch. The ontogenetic trajectory, composed of alternating steps and thresholds, was interpreted as saltatory. In comparison with other flatfishes, H. hippoglossus exhibits delayed onset of chondrification. From 9 dph onwards, the ontogenetic trajectory resembles more than that of the turbot Psetta maxima than that of the common sole Solea solea or the summer flounder Paralichthys dentatus and winter flounder Pseudopleuronectes americanus. Hippoglossus hippoglossus with the gaping-jaw malformation, common in intensively cultured individuals of this species, were examined histologically. The reason larvae cannot close their mouth, as their yolk-sac resorbs, seems to be related to the fusion of the interhyal to the hyosymplectic and ceratohyal with which it is normally articulated.

  • Dynamic Skeletogenesis in Fishes: Insight of Exercise Training on Developmental Plasticity

    Developmental Dynamics

    Background: Through developmental and evolutionary time, organisms respond variably to their environment not only in terms of size and shape but also in term of timing. Developmental plasticity can potentially act on various aspects of the timing of developmental events. When dealing with the chondrification and ossification of the vertebrate skeleton, developmental properties include the onset, offset, duration of events, transitions of skeletal states, order of events in a sequence, and the trajectories of developmental events. We studied the phenotypic response of median fin endoskeleton in developing newly-hatched Arctic charr (Salvelinus alpinus) under differential water velocity. Results: Developmental progress of chondrification in all fins is less influenced than ossification by an increase of water velocity. The most responsive elements, meaning those elements with greater onset plasticity owing to a water velocity increase, differ in terms of early versus late developmental events. The most responsive elements are those that chondrify and to a greater extent ossify later in the development. Conclusions: Plasticity is documented for the timing of onset and the transition of skeletal states rather than the order of events within a sequence. Similarities of plastic response in developmental patterns could be used as a powerful criterion to strengthen the identification of phenotypic modules.

  • Elpistostege and the light and dark side of the moon: New data on the paleoenvironment of the fish-to-tetrapod transition

    Journal of Vertebrate Paleontology, Supplement

    Paleoenvironmental considerations of the fish-to-tetrapod transition have suggested that early tetrapods and their closest relatives, the elpistostegalian fishes, were exploiting a range of habitats. Three Middle-Late Devonian elpistostegalian taxa are most critical to understand this environmental-evolutionary transition. The late Givetian Panderichthys is associated with a deltaic environment, whereas the early-middle Frasnian Tiktaalik is associated with a non-marine depositional setting. The middle Frasnian Elpistostege watsoni is preserved in the renowned Escuminac Formation (Miguasha, Quebec, Canada), a siliciclastic formation interpreted as an estuarine environment. Based on sequential stratigraphy, the Escuminac Formation (119 m) was recently characterized by five transgressive/regressive sequences within an inner wave-dominated estuary showing shifts in continentalization. Furthermore, isotopic (Rb-Sr) analyses of bioapatites support a brackish to marine environment. All known Elpistostege material, including the very first complete specimen recently discovered, has been found in laminated horizons associated with transgressive or highstand components of the stratigraphic sequences. The new specimen has been found in association with the acanthodian Triazeugacanthus and Homalacanthus, the conchostracan Asmusia and the lignophyte Archaeopteris, in a horizon displaying a regular alternation of dark (clay and amorphous organic matter) and light (silt-size calcite and quartz) laminae forming couplets. Individual lamina thicknesses were measured on high resolution digital images of the enclosing bed in order to evaluate the pattern of thickness variation...

  • External morphology of the Devonian Placoderm Bothriolepis canadensis

    Journal of Vertebrate Paleontology, Supplement

    The external morphology of the well-known, middle Frasnian Bothriolepis canadensis from the Escuminac Formation (Miguasha, Canada) is revised using cutting- edge technology in three-dimensional (3D) digital imagery. Nineteen well-preserved and articulated specimens of B. canadensis were used to reconstruct a 3D digital model of the dermal armor (cephalic and thoracic parts covering 35.6% of the total length), whereas four specimens were used to reconstruct the posterior part of the body. The 3D model representing a large adult specimen (44 cm total length) allows us to investigate some biomechanical aspects and constraints. Mobility of the cephalic armor, submarginal plates (“opercular plates”) and pectoral fins has been previously hypothesized based on inaccurate reconstructions. In contrast to previous reconstructions, there is no indication of mobility between the cephalic and thoracic armors. The submarginal plate is fixed upon the cephalic armor; a gill opening is located between the submarginal plate and the anterior ventrolateral plate of the thoracic armor. The median dorsal ridge of the thoracic armor forms a hydrodynamic dorsal crest with its maximum height along the posterior median dorsal plate. In contrast to previous interpretations, the fully retracted and protracted (70o) position of the pectoral fin allows only for restricted movement. Maximum of mobility is reached in a protracted angle of 16o which allows a rotation of 30o around the brachial process and 20o in an up-and-down movement. The 3D model of B. canadensis brings out some unexpected novelties on a supposedly well-known Devonian fish.

  • New methodology for 3D reconstruction of fossil fish using digital imagery

    Journal of Vertebrate Paleontology, Supplement

    Non-invasive technologies, such as CT-scan, traditional and synchrotron-based micro-CT-scan, are gaining in popularity for quantitative visualization of fossilized anatomical structures and ultrastructures. However, most studies in virtual paleontology are performed on a limited number of specimens owing to the cost of utilisation and the time required for image acquisition, processing, and interpretation. Usage of such technologies can also be limited by the taphonomic condition and size of the fossils, as well as the type of matrix surrounding the specimens. However, three-dimensional reconstruction (3D) of taxon does not necessarily require histological and ultrastructural investigation. Non-invasive 3D laser surface scanner provides the possibility to acquire high-definition surface-scanned images of prepared specimens without the potential limitations imposed by other technologies. Results are rapid and easy to use for research purpose and collection management. A new and precise method to 3D-reconstruct fossilized taxon was developed using a 3D laser surface scanner combined with cutting- edge digital imagery tools. Nineteen well-preserved and articulated specimens of the Late Devonian placoderm Bothriolepis canadensis (Miguasha, eastern Canada) were scanned at maximum resolution. Digital data were cleaned in an acquisition and processing software. Using a digital sculpting software, superposition of multiple 3D meshed models allows for size and shape corrections and taphonomical corrections providing an unbiased and accurate reconstruction of B. canadensis. This new digital reconstruction highlights previous anatomical misinterpretations on the morphology, size and shape, and articulation of this placoderm; most of the modifications would not have been possible without the usage of the digital 3D model.

  • Great Canadian Lagerstätten 4. The Devonian Miguasha biota (Quebec): an UNESCO World Heritage, a time capsule in the early history of vertebrates

    Geoscience Canada

    Over the past 170 years, the Late Devonian Miguasha biota from eastern Canada has yielded a diverse aquatic assemblage including 20 species of lower vertebrates (anaspids, osteostracans, placoderms, acanthodians, actinopterygians and sarcopterygians), a more limited invertebrate assemblage, and a continental component including plants, scorpions and millipedes. Originally interpreted as a freshwater lacustrine environment, recent paleontological, taphonomic, sedimentological and geochemical evidence corroborates a brackish estuarine setting. Over 18,000 fish specimens have been recovered showing various modes of fossilization, including uncompressed material and soft-tissue preservation. Most vertebrates are known from numerous, complete, articulated specimens. Exceptionally well-preserved larval and juvenile specimens have been identified for 14 out of the 20 species of fishes, allowing growth studies. Numerous horizons within the Escuminac Formation are now interpreted as either Konservat– or Konzentrat–Lagerstätten.

  • A new piece of the Devonian fish-to-tetrapod puzzle: The discovery of a complete specimen of Elpistostege

    Journal of vertebrate paleontology

    Recent hypotheses on the origin of tetrapods rely heavily on the anatomy of only a few tetrapod-like fossils from the Middle-Upper Devonian. These tetrapod-like taxa, referred to as elpistostegalians, constitute a paraphyletic group including Panderichthys rhombolepis from the late Givetian of Latvia, Elpistostege watsoni from the middle Frasnian of Quebec, and Tiktaalik roseae from the early-middle Frasnian of Arctic Canada. Although of uncertain phylogenetic position, Gogonasus andrewsaea from the early Frasnian of Western Australia and Livoniana multidentata from the late Givetian of Latvia and Estonia have also been suggested to be closely related to elpistostegalians. With the exception of Livoniana (fragments of lower jaw) and Elpistostege (two partial skulls and a small trunk segment), the anatomy of Panderichthys and Tiktaalik is fairly well documented. The recent discovery of a 1.56 m-long, completely articulated specimen of Elpistostege watsoni from the Escuminac Formation (Miguasha) is filling out a major gap of anatomical information with respect to the fish-to-tetrapod transition. Elpistostege has elongated trunk and caudal regions with oversized pectoral fins. A high- energy CT-scan investigation of the complete specimen reveals internal cranial and paired fin anatomy. This makes it the most complete elpistostegalian known allowing us to reinvestigate its phylogenetic position. Elpistostege is unambiguously more closely related to Tiktaalik and early tetrapods than to Panderichthys.

  • A new piece of the Devonian fish-to-tetrapod puzzle: The discovery of a complete specimen of Elpistostege

    Journal of Vertebrate Paleontology, Supplement

    Recent hypotheses on the origin of tetrapods rely heavily on the anatomy of only a few tetrapod-like fossils from the Middle-Upper Devonian. These tetrapod-like taxa, referred to as elpistostegalians, constitute a paraphyletic group including Panderichthys rhombolepis from the late Givetian of Latvia, Elpistostege watsoni from the middle Frasnian of Quebec, and Tiktaalik roseae from the early-middle Frasnian of Arctic Canada. Although of uncertain phylogenetic position, Gogonasus andrewsaea from the early Frasnian of Western Australia and Livoniana multidentata from the late Givetian of Latvia and Estonia have also been suggested to be closely related to elpistostegalians. With the exception of Livoniana (fragments of lower jaw) and Elpistostege (two partial skulls and a small trunk segment), the anatomy of Panderichthys and Tiktaalik is fairly well documented. The recent discovery of a 1.56 m-long, completely articulated specimen of Elpistostege watsoni from the Escuminac Formation (Miguasha) is filling out a major gap of anatomical information with respect to the fish-to-tetrapod transition. Elpistostege has elongated trunk and caudal regions with oversized pectoral fins. A high- energy CT-scan investigation of the complete specimen reveals internal cranial and paired fin anatomy. This makes it the most complete elpistostegalian known allowing us to reinvestigate its phylogenetic position. Elpistostege is unambiguously more closely related to Tiktaalik and early tetrapods than to Panderichthys.

  • Profile of a Devonian killer: Eusthenopteron foordi, top-predator of the Escuminac fish assemblage

    Journal of Vertebrate Paleontology, Supplement

    In recent ecosystems, opportunistic predators restrain community interactions by applying a top-down control on interspecific relationships. The Upper Devonian Miguasha Fossil-Lagerstätte (Quebec, eastern Canada) provides the opportunity to describe part of the ecological structure of this paleocommunity owing to the exceptionalstate of preservation and the high concentration of fossil fishes. The Escuminac assemblage includes 20 vertebrate species belonging to anaspids, osteostracans, placoderms, acanthodians, actinopterygians and sarcopterygians. Ecomorphological (based on non-metric multidimensional scaling) and 3D modelling approaches on all Escuminac fish species provided (1) a structural pattern for the predator-prey relationships and (2) new elements (i.e., bottom-up versus top-down control on interspecific relationships) to understand the paleoecological persistence of the ecosystem through time. Among the 20 vertebrate species, the osteolepiform Eusthenopteron foordi is interpreted as the top-predator of the assemblage. Digestive tract contents have been observed in 66 specimens of E. foordi of which 36% contain identifiable preys. Evidence of foraging by E. foordi has been recorded on five vertebrate species (i.e., Bothriolepis canadensis, Homalacanthus concinnus, Cheirolepis canadensis, Scaumenacia curta and E. foordi) and on conchostracans. The preservation of full-size ingested prey items provides new insights on the anatomy of the gastrointestinal tract of E. foordi and its capacity to contain large prey items (up to 86% of the predator length). The predation mode of E. foordi shows behavioral and morphological similarities with extant aquatic top-predators. Opportunistic predation and the abundance and richness of lower trophic level in aquatic Devonian ecosystems, such as the Escuminac paleoestuary, constrained the trophic structure of the fish biota.