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Showing 1–13 of 13 results
Advanced filters: Author: Zerina Johanson Clear advanced filters

  • The authors explore dental development in a stem-chondrichthyan ischnacanthid acanthodian to inform our understanding of the ancestral gnathostome dental condition, finding that although dermal oral tubercles are a conserved feature of early gnathostomes, the complex cyclic shedding dentitions and whorls appear to have evolved multiple times.

    • Martin Rücklin
    • Benedict King
    • Philip C. J. Donoghue
    Research
    Nature Ecology & Evolution
    Volume: 5, P: 919-926

  • The discovery of claspers in fossils of antiarch placoderms, an ancient group of armoured fish, suggests that internal fertilization was the ancestral type of reproduction for all jawed vertebrates: this contrasts with the current understanding that external fertilization must be the ancestral state.

    • John A. Long
    • Elga Mark-Kurik
    • Kate Trinajstic
    Research
    Nature
    Volume: 517, P: 196-199

  • The placoderms are a large group of primitive armoured fishes, which, although now extinct, could shed light on the evolution of jawed vertebrates. Recent fossil finds have been discovered with embryos, illustrating that fertilization was internal, but direct evidence for this was missing. Here, the discovery of a completely ossified pelvic clasper in a male Incisoscutum ritchiei confirms internal fertilization in arthrodires, a large and important placoderm group.

    • Per Ahlberg
    • Kate Trinajstic
    • John Long
    Research
    Nature
    Volume: 460, P: 888-889

  • This paper reveals evidence of embryos within Incisoscutum (a member of the arthrodires, a large, important and diverse group of placoderms). Incisoscutum had pelvic girdles of the right structure to support organs like the claspers of sharks, which are used in internal fertilization. The find confirms that internal fertilization and viviparity were much more widespread among the earliest jawed vertebrates than had previously been appreciated.

    • John A. Long
    • Kate Trinajstic
    • Zerina Johanson
    Research
    Nature
    Volume: 457, P: 1124-1127

  • Synchrotron radiation X-ray tomographic microscopy of a developmental series of Compagopiscis croucheri (Arthrodira) indicates that placoderms had true teeth, but that tooth and jaw development was not developmentally or structurally integrated in placoderms.

    • Martin Rücklin
    • Philip C. J. Donoghue
    • Marco Stampanoni
    Research
    Nature
    Volume: 491, P: 748-751

  • Computed tomography analysis of the braincase of the Early Devonian placoderm fish Kolymaspis sibirica suggests a skeletal gill support was involved in the origin of the shoulder girdle and provides new evidence reconciling historic theories about the evolution of paired fins.

    • Martin D. Brazeau
    • Marco Castiello
    • Matt Friedman
    ResearchOpen Access
    Nature
    Volume: 623, P: 550-554

  • Computed tomography reveals that the cranial anatomy of Ordovician stem-group gnathostome Eriptychius americanus from the Harding Sandstone of Colorado, USA, is distinct among vertebrates.

    • Richard P. Dearden
    • Agnese Lanzetti
    • Ivan J. Sansom
    ResearchOpen Access
    Nature
    Volume: 621, P: 782-787

  • The authors report a fossilized vertebrate rib with spiked dermal armour fused to its dorsal surface from the mid-Jurassic of Morocco, which they interpret as the earliest known ankylosaur.

    • Susannah C. R. Maidment
    • Sarah J. Strachan
    • Paul M. Barrett
    Research
    Nature Ecology & Evolution
    Volume: 5, P: 1576-1581