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    Wyświetlanie 1-3 z 3
    Tytuł:
    Geometric morphometric analysis and taxonomic revision of the Gzhelian (Late Pennsylvanian) conodont Idiognathodus simulator from North America
    Autorzy:
    HOGANCAMP, NICHOLAS J.
    BARRICK, JAMES E.
    STRAUSS, RICHARD E.
    Powiązania:
    https://bibliotekanauki.pl/articles/945657.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    conodonta
    idiognathodus
    morphometrics
    pennsylvanian
    gzhelian
    north america
    midcontinent
    Opis:
    A new morphometric approach was developed to study morphological variation within P1 elements commonly referred to as Idiognathodus simulator, which was selected to be the biostratigraphic marker for the base of the global Gzhelian Stage (Carboniferous). This new approach combines landmark-based geometric morphometrics with eigen analyses to analyze shape variation within P1 elements of the I. simulator group, and could be used to analyze shape variation in other morphologically similar conodont groups. Specimens analyzed were obtained from three sections of the early Gzhelian Heebner Shale of the Oread cyclothem in the North American Midcontinent region, the cyclothem from which I. simulator was originally named. This analysis shows that the I. simulator group comprises a set of at least five species with asymmetrical P1 element pairs, relatively short adcarinal ridges, and a variably developed eccentric groove. Species discrimination is based on the presence of caudal and rostral lobes, character of the adcarinal ridges, and platform shape. The species I. simulator is restricted to P1 elements with a caudal adcarinal ridge that is isolated from the caudal platform margin. Idiognathodus lateralis sp. nov. is erected to include P1 elements with a caudal adcarinal ridge that is not isolated from the caudal platform margin.
    Źródło:
    Acta Palaeontologica Polonica; 2016, 61, 3; 477-502
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Postcranial osteology of the first early-stage juvenile skeleton of Plateosaurus trossingensis from the Norian of Frick, Switzerland
    Autorzy:
    Nau, D.
    Lallensack, J.N.
    Bachmann, U.
    Sander, P.M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2082237.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    Dinosauria
    Sauropodomorpha
    morphometrics
    morphology
    small body size
    early ontogeny
    Triassic
    Swiss Plateau
    Opis:
    Owing to monospecific mass-accumulation sites in Central Europe, the early-branching sauropodomorph Plateosaurus has one of the best fossil records among dinosaurs. Despite this, early-stage juveniles have been conspicuously absent. However, such specimens are critical in assessing the ontogenetic development of this taxon, as well as the role of heterochrony in sauropodomorph evolution. A new skeleton from the Plateosaurus bonebed at the Gruhalde Quarry (Klettgau Formation, Norian) of Frick, Switzerland, nicknamed “Fabian”, represents the first substantially complete juvenile referrable to Plateosaurus. The specimen includes large portions of the cranium and vertebral column and an almost completely represented appendicular skeleton. Its juvenile ontogenetic stage is confirmed by a lack of neurocentral suture fusion in the axial skeleton. Consistent with this, the estimated total length and body mass of approximately of 2.3 m and 40 kg are considerably smaller than any previously reported specimen of the genus. Surprisingly, the postcranial morphology of the specimen is remarkably consistent with that of osteologically mature individuals, including a virtually fully developed pattern of laminae and fossae in the vertebrae. Comparisons of body proportions are complicated by varying degrees of compaction in the limb elements, but skeletal proportions mostly appear to follow isometry, with the notable exceptions of a relatively long neck, proportionately larger manus, shorter, more gracile humerus and shorter forearm in the juvenile specimen. The observed morphology suggests that adult morphology was either achieved early in ontogeny of Plateosaurus, or alternatively that developmental plasticity, which has previously been found to result in high variability of adult body size, could potentially also extend to morphological development.
    Źródło:
    Acta Palaeontologica Polonica; 2020, 65, 4; 679-708
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Ontogenetic changes in the craniomandibular skeleton of the abelisaurid dinosaur Majungasaurus crenatissimus from the Late Cretaceous of Madagascar
    Autorzy:
    Ratsimbaholison, N.O.
    Felice, R.N.
    O’Connor, P.M.
    Powiązania:
    https://bibliotekanauki.pl/articles/21868.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Instytut Paleobiologii PAN
    Tematy:
    ontogenetic change
    craniomandibular skeleton
    abelisaurid dinosaur
    Majungasaurus crenatissimus
    Dinosauria
    Abelisauridae
    geometric morphometrics
    ontogenesis
    skull
    Cretaceous
    Gondwana
    Late Cretaceous
    Madagascar
    Opis:
    Abelisaurid theropods were one of the most diverse groups of predatory dinosaurs in Gondwana during the Cretaceous. The group is characterized by a tall, wide skull and robust cervical region. This morphology is thought to have facilitated specialized feeding behaviors such as prolonged contact with prey. The Late Cretaceous abelisaurid Majungasaurus crenatissimus typifies this abelisaurid cranial morphotype. Recent fossil discoveries of this species include a partial growth series that allows for the first time an investigation of ontogenetic variation in cranial morphology in a representative abelisaurid. Herein we examine growth trajectories in the shape of individual cranial bones and articulated skulls of Majungasaurus using geometric morphometrics. Several major changes in skull shape were observed through ontogeny, including an increase in the height of the jugal, postorbital, and quadratojugal, an increase in the extent of the contacts between bones, and a decrease in the circumference of the orbit. The skull transitions from relatively short in the smallest individual to tall and robust in large adults, as is seen in other theropods. Such morphological change during ontogeny would likely have resulted in different biomechanical properties and feeding behaviors between small and large individuals. These findings provide a post-hatching developmental framework for understanding the evolution of the distinctive tall skull morphology seen in abelisaurids and other large-sized theropod dinosaurs.
    Źródło:
    Acta Palaeontologica Polonica; 2016, 61, 2
    0567-7920
    Pojawia się w:
    Acta Palaeontologica Polonica
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-3 z 3

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