Search for dissertations about: "Zerina Johanson"

Found 2 swedish dissertations containing the words Zerina Johanson.

  2. 1. The Origin of Tooth Replacement : Three-dimensional Synchrotron Histology Visualizes the Dental Development of Silurian Stem Osteichthyans

    Author : Donglei Chen; Per Ahlberg; Zerina Johanson; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES;

    Abstract : Mechanisms of tooth replacement distribute incongruently among extant gnathostomes (jawed vertebrates): a permanent tooth-generating dental lamina exists in chondrichthyans (cartilaginous fish) and tetrapods but not teleosts, whereas tooth shedding by basal hard tissue resorption occurs in tetrapods and teleosts but not chondrichthyans. Theories about the evolution of tooth development have been biased towards the chondrichthyan conveyor-belt replacement, since there has been no fossil evidence for the origin of osteichthyan (bony fish and tetrapods) tooth replacement until now. READ MORE

  4. 2. Morphology, Taxonomy and Interrelationships of Tristichopterid Fishes (Sarcopterygii, Tetrapodomorpha)

    Author : Daniel Snitting; Per Erik Ahlberg; Graham Budd; Henning Blom; Zerina Johanson; Uppsala universitet; []
    Keywords : Organismic biology; Sarcopterygii; Tetrapodomorpha; Tristichopteridae; biogeography; phylogeny; Computed Tomography; Devonian; Organismbiologi;

    Abstract : Tristichopterids (Sarcopterygii, Tetrapodomorpha) form a monophyletic group of exclusively Devonian fishes. This thesis consists of descriptions of new material of tristichopterids and closely related taxa, as well as new interpretations and descriptions of previously figured material. READ MORE