Desmograptus micronematoides, a Silurian dendroid graptolite, and its ultrastructure

Kate M. Saunders, Denis E. B. Bates, Joanne Kluessendorf, David Loydell, Donald G. Mikulic

    Research output: Contribution to journalArticlepeer-review


    Desmograptus micronematodes from Thornton quarry, Cook County, Illinois, USA, remarkably preserved in relief and encased in pyrite, is described. The internal details of the thecae, and of the stolon system, examined using the SEM, allow the reconstruction of the growth of a stipe. The stolons and stolonal nodes are formed of a dense crassal fabric, and are surrounded by a loose fabric of three-dimensional fibrils. The nodes have a complex structure of three boxes with proximal and distal nozzles. The base of a bitheca, and the base of each autothecal cup, has a central nozzle surrounded by a unique honeycomb fabric. The ultrastructure of the cortical fibrils, with their clockwise striations, is similar to that in Dendrograptus, and may be universal in the graptolites. The nodes of the stolon system appear identical to those of Acanthograptus and other dendroids, but differ from those of the extant hemichordate Rhabdopleura, which have only a diaphragm, and lack box structures.
    Original languageEnglish
    Pages (from-to)541-559
    Number of pages19
    Issue number3
    Publication statusPublished - May 2009


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