Gavialis

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Christopher A. Brochu - One of the best experts on this subject based on the ideXlab platform.

  • An Expanded Combined Evidence Approach to the Gavialis Problem Using Geometric Morphometric Data from Crocodylian Braincases and Eustachian Systems
    2016
    Co-Authors: Maria Eugenia, Christopher A. Brochu, Leone Gold, Mark A. Norell
    Abstract:

    The phylogenetic position of the Indian gharial (Gavialis gangeticus) is disputed- morphological characters place Gavialis as the sister to all other extant crocodylians, whereas molecular and combined analyses find Gavialis and the false gharial (Tomistoma schlegelii) to be sister taxa. Geometric morphometric techniques have only begun to be applied to this issue, but most of these studies have focused on the exterior of the skull. The braincase has provided useful phylogenetic information for basal crurotarsans, but has not been explored for the crown group. The Eustachian system is thought to vary phylogenetically in Crocodylia, but has not been analytically tested. To determine if gross morphology of the crocodylian braincase proves informative to the relationships of Gavialis and Tomistoma, we used two- and three-dimensional geometric morphometric approaches. Internal braincase images were obtained using high-resolution computerized tomography scans. A principal components analysis identified that the first component axis was primarily associated with size and did not show groupings that divide the specimens by phylogenetic affinity. Sliding semi-landmarks and a relative warp analysis indicate that a unique Eustachian morphology separates Gavialis from other extant members of Crocodylia. Ontogenetic expansion of the braincase results in a more dorsoventrally elongate median Eustachian canal. Changes in the shape of the Eustachian system do provide phylogenetic distinctions between major crocodylian clades. Each morphometric dataset, consisting of continuous morphological characters, was added independently to a combined cladistic analysis of discret

  • An expanded combined evidence approach to the Gavialis problem using geometric morphometric data from crocodylian braincases and Eustachian systems.
    PLOS ONE, 2014
    Co-Authors: Maria Eugenia Leone Gold, Christopher A. Brochu, Mark A. Norell
    Abstract:

    The phylogenetic position of the Indian gharial (Gavialis gangeticus) is disputed - morphological characters place Gavialis as the sister to all other extant crocodylians, whereas molecular and combined analyses find Gavialis and the false gharial (Tomistoma schlegelii) to be sister taxa. Geometric morphometric techniques have only begun to be applied to this issue, but most of these studies have focused on the exterior of the skull. The braincase has provided useful phylogenetic information for basal crurotarsans, but has not been explored for the crown group. The Eustachian system is thought to vary phylogenetically in Crocodylia, but has not been analytically tested. To determine if gross morphology of the crocodylian braincase proves informative to the relationships of Gavialis and Tomistoma, we used two- and three-dimensional geometric morphometric approaches. Internal braincase images were obtained using high-resolution computerized tomography scans. A principal components analysis identified that the first component axis was primarily associated with size and did not show groupings that divide the specimens by phylogenetic affinity. Sliding semi-landmarks and a relative warp analysis indicate that a unique Eustachian morphology separates Gavialis from other extant members of Crocodylia. Ontogenetic expansion of the braincase results in a more dorsoventrally elongate median Eustachian canal. Changes in the shape of the Eustachian system do provide phylogenetic distinctions between major crocodylian clades. Each morphometric dataset, consisting of continuous morphological characters, was added independently to a combined cladistic analysis of discrete morphological and molecular characters. The braincase data alone produced a clade that included crocodylids and Gavialis, whereas the Eustachian data resulted in Gavialis being considered a basally divergent lineage. When each morphometric dataset was used in a combined analysis with discrete morphological and molecular characters, it generated a tree that matched the topology of the molecular phylogeny of Crocodylia.

  • Landmark configurations for the braincase (A) and Eustachian systems (B).
    2014
    Co-Authors: Maria Eugenia Leone Gold, Christopher A. Brochu, Mark A. Norell
    Abstract:

    A: The braincase analysis used 15 Type I and Type II landmarks (Table 1). Specimen number AMNH R15163 Crocodylus acutus. B: Exemplary midsagittal slice and landmark placement for Eustachian system analysis. Inset diagram shows the landmark configuration. Black circles with white borders are Type I and II landmarks; white circles with black borders are sliding semi-landmarks. Specimen number AMNH R81802 Gavialis gangeticus.

  • Plot of RW1 versus RW2 from the 2D analysis of the Eustachian system.
    2014
    Co-Authors: Maria Eugenia Leone Gold, Christopher A. Brochu, Mark A. Norell
    Abstract:

    Larger and smaller specimens are located towards the positive and negative ends of RW1, respectively. Members of Alligatoridae (orange) generally overlap with members of Crocodylidae (blue). Tomistoma (purple) overlaps with both Alligatoridae and Crocodylidae. Gavialis (green) occupies morphospace that is mostly unoccupied by other crocodylians, except the smallest Gavials, which overlaps the Tomistoma morphospace. Inset diagrams at the extremes of each axis show the landmark configuration for the starred location on that axis. Along RW1, Larger specimens have a more vertically oriented Eustachian canal than smaller specimens, for which the canal is more horizontal. Changes along RW2 have to do with the relative shape of the anterior and posterior Eustachian canals.

  • Phylogenetic tree from morphological and molecular data (left) and total evidence (right), with Alligatoroidea collapsed.
    2014
    Co-Authors: Maria Eugenia Leone Gold, Christopher A. Brochu, Mark A. Norell
    Abstract:

    Both analyses return Gavialis within Crocodylidae, supporting the molecular hypothesis of Crocodylia. The morphological and molecular data created 360 MPTs length of length 17534. The total evidence tree resulted in 360 MPTs length 17541.530. The strict consensus of each is shown. Numbers in boxes denote clades: 1 - Crocodylidae, 2 - Gavialidae. Bootstrap and Bremer values are shown above and below each corresponding node, respectively. Red branches indicate different relationships between the two trees.

Rayfield Emily - One of the best experts on this subject based on the ideXlab platform.

Ballell Antonio - One of the best experts on this subject based on the ideXlab platform.

  • Data from: Convergence and functional evolution of longirostry in crocodylomorphs
    2019
    Co-Authors: Ballell Antonio, Moon, Benjamin C., Porro, Laura B., Benton, Michael J., Rayfield, Emily J.
    Abstract:

    During the Mesozoic, Crocodylomorpha had a much higher taxonomic and morphological diversity than today. Members of one particularly successful clade, Thalattosuchia, are well-known for being longirostrine: having long, slender snouts. It has generally been assumed that Thalattosuchia owed their success in part to the evolution of longirostry, leading to a feeding ecology similar to that of the living Indian gharial, Gavialis. Here, we compare form and function of the skulls of the thalattosuchian Pelagosaurus and Gavialis using digital reconstructions of the skull musculoskeletal anatomy and finite element models to show that they had different jaw muscle arrangements and biomechanical behaviour. Additionally, the relevance of feeding-related mandibular traits linked to longirostry in the radiation of crocodylomorph clades was investigated by conducting an evolutionary rates analysis under the variable rates model. We find that, even though Pelagosaurus and Gavialis share similar patterns of stress distribution in their skulls, the former had lower mechanical resistance. This suggests that compared to Gavialis, Pelagosaurus was unable to process large, mechanically less tractable prey, instead operating as a specialised piscivore that fed on softer and smaller prey. Secondly, innovation of feeding strategies was achieved by rate acceleration of functional characters of the mandible, a key mechanism for the diversification of certain clades like thalattosuchians and eusuchians. Different rates of functional evolution suggest divergent diversification dynamics between teleosaurids and metriorhynchids in the Jurassic

  • Gavialis cranium unilateral anterior
    2019
    Co-Authors: Ballell Antonio, Moon Benjamin, Porro Laura, Benton Michael, Rayfield Emily
    Abstract:

    Abaqus input file of Gavialis cranium simulating an unilateral anterior bite

  • Gavialis mandible bilateral middle
    2019
    Co-Authors: Ballell Antonio, Moon Benjamin, Porro Laura, Benton Michael, Rayfield Emily
    Abstract:

    Abaqus input file of Gavialis mandible simulating a bilateral middle bite

  • Gavialis cranium bilateral posterior
    2019
    Co-Authors: Ballell Antonio, Moon Benjamin, Porro Laura, Benton Michael, Rayfield Emily
    Abstract:

    Abaqus input file of Gavialis cranium simulating a bilateral posterior bite

  • Gavialis mandible unilateral anterior
    2019
    Co-Authors: Ballell Antonio, Moon Benjamin, Porro Laura, Benton Michael, Rayfield Emily
    Abstract:

    Abaqus input file of Gavialis mandible simulating an unilateral anterior bite

Mark A. Norell - One of the best experts on this subject based on the ideXlab platform.

  • An Expanded Combined Evidence Approach to the Gavialis Problem Using Geometric Morphometric Data from Crocodylian Braincases and Eustachian Systems
    2016
    Co-Authors: Maria Eugenia, Christopher A. Brochu, Leone Gold, Mark A. Norell
    Abstract:

    The phylogenetic position of the Indian gharial (Gavialis gangeticus) is disputed- morphological characters place Gavialis as the sister to all other extant crocodylians, whereas molecular and combined analyses find Gavialis and the false gharial (Tomistoma schlegelii) to be sister taxa. Geometric morphometric techniques have only begun to be applied to this issue, but most of these studies have focused on the exterior of the skull. The braincase has provided useful phylogenetic information for basal crurotarsans, but has not been explored for the crown group. The Eustachian system is thought to vary phylogenetically in Crocodylia, but has not been analytically tested. To determine if gross morphology of the crocodylian braincase proves informative to the relationships of Gavialis and Tomistoma, we used two- and three-dimensional geometric morphometric approaches. Internal braincase images were obtained using high-resolution computerized tomography scans. A principal components analysis identified that the first component axis was primarily associated with size and did not show groupings that divide the specimens by phylogenetic affinity. Sliding semi-landmarks and a relative warp analysis indicate that a unique Eustachian morphology separates Gavialis from other extant members of Crocodylia. Ontogenetic expansion of the braincase results in a more dorsoventrally elongate median Eustachian canal. Changes in the shape of the Eustachian system do provide phylogenetic distinctions between major crocodylian clades. Each morphometric dataset, consisting of continuous morphological characters, was added independently to a combined cladistic analysis of discret

  • An expanded combined evidence approach to the Gavialis problem using geometric morphometric data from crocodylian braincases and Eustachian systems.
    PLOS ONE, 2014
    Co-Authors: Maria Eugenia Leone Gold, Christopher A. Brochu, Mark A. Norell
    Abstract:

    The phylogenetic position of the Indian gharial (Gavialis gangeticus) is disputed - morphological characters place Gavialis as the sister to all other extant crocodylians, whereas molecular and combined analyses find Gavialis and the false gharial (Tomistoma schlegelii) to be sister taxa. Geometric morphometric techniques have only begun to be applied to this issue, but most of these studies have focused on the exterior of the skull. The braincase has provided useful phylogenetic information for basal crurotarsans, but has not been explored for the crown group. The Eustachian system is thought to vary phylogenetically in Crocodylia, but has not been analytically tested. To determine if gross morphology of the crocodylian braincase proves informative to the relationships of Gavialis and Tomistoma, we used two- and three-dimensional geometric morphometric approaches. Internal braincase images were obtained using high-resolution computerized tomography scans. A principal components analysis identified that the first component axis was primarily associated with size and did not show groupings that divide the specimens by phylogenetic affinity. Sliding semi-landmarks and a relative warp analysis indicate that a unique Eustachian morphology separates Gavialis from other extant members of Crocodylia. Ontogenetic expansion of the braincase results in a more dorsoventrally elongate median Eustachian canal. Changes in the shape of the Eustachian system do provide phylogenetic distinctions between major crocodylian clades. Each morphometric dataset, consisting of continuous morphological characters, was added independently to a combined cladistic analysis of discrete morphological and molecular characters. The braincase data alone produced a clade that included crocodylids and Gavialis, whereas the Eustachian data resulted in Gavialis being considered a basally divergent lineage. When each morphometric dataset was used in a combined analysis with discrete morphological and molecular characters, it generated a tree that matched the topology of the molecular phylogeny of Crocodylia.

  • Landmark configurations for the braincase (A) and Eustachian systems (B).
    2014
    Co-Authors: Maria Eugenia Leone Gold, Christopher A. Brochu, Mark A. Norell
    Abstract:

    A: The braincase analysis used 15 Type I and Type II landmarks (Table 1). Specimen number AMNH R15163 Crocodylus acutus. B: Exemplary midsagittal slice and landmark placement for Eustachian system analysis. Inset diagram shows the landmark configuration. Black circles with white borders are Type I and II landmarks; white circles with black borders are sliding semi-landmarks. Specimen number AMNH R81802 Gavialis gangeticus.

  • Plot of RW1 versus RW2 from the 2D analysis of the Eustachian system.
    2014
    Co-Authors: Maria Eugenia Leone Gold, Christopher A. Brochu, Mark A. Norell
    Abstract:

    Larger and smaller specimens are located towards the positive and negative ends of RW1, respectively. Members of Alligatoridae (orange) generally overlap with members of Crocodylidae (blue). Tomistoma (purple) overlaps with both Alligatoridae and Crocodylidae. Gavialis (green) occupies morphospace that is mostly unoccupied by other crocodylians, except the smallest Gavials, which overlaps the Tomistoma morphospace. Inset diagrams at the extremes of each axis show the landmark configuration for the starred location on that axis. Along RW1, Larger specimens have a more vertically oriented Eustachian canal than smaller specimens, for which the canal is more horizontal. Changes along RW2 have to do with the relative shape of the anterior and posterior Eustachian canals.

  • Phylogenetic tree from morphological and molecular data (left) and total evidence (right), with Alligatoroidea collapsed.
    2014
    Co-Authors: Maria Eugenia Leone Gold, Christopher A. Brochu, Mark A. Norell
    Abstract:

    Both analyses return Gavialis within Crocodylidae, supporting the molecular hypothesis of Crocodylia. The morphological and molecular data created 360 MPTs length of length 17534. The total evidence tree resulted in 360 MPTs length 17541.530. The strict consensus of each is shown. Numbers in boxes denote clades: 1 - Crocodylidae, 2 - Gavialidae. Bootstrap and Bremer values are shown above and below each corresponding node, respectively. Red branches indicate different relationships between the two trees.

Emily Rayfield - One of the best experts on this subject based on the ideXlab platform.

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