TAYLOR, THOMAS1*, HAGEN HASS2, HANS KERP2, and MICHAEL KRINGS2. 1Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS 66045 USA; 2Geologische-Paläontologische Institut und Museum, Westfälische Wilhelms-Universität, Münster, Germany. - Ascomycetes in the Rhynie chert.
In recent years studies of the Rhynie chert have contributed
appreciably to our understanding of the fungi that existed during the
Lower Devonian. One of the recently documented groups is the
ascomycetes, the largest group of true fungi with nearly two thousand
genera. The principal morphological feature of ascomycetes is the
sac-like ascus in which sexual ascospores are produced. Sections of
Asteroxylon aerial stems and rhizomes have been discovered that
contain numerous perithecia that appear just below the epidermis,
often associated with a stomatal complex. In a few specimens
perithecia occur at the base of enations. Perithecia are
globose-spherical and possess a slightly elongate neck. The ostiole is
lined with periphyses. Extending from a two-layered hymenium are
elongate paraphyses and unitunicate asci. Ascospores may be
uni-multicelled, elongate, and demonstrate germination at either end.
Also present on some axes are unbranched conidiophores and cube-shaped
arthrospores produced by segmentation of side branches. The fossil
ascomycetes provide critical information about this unique group of
true fungi, and offer important characters that can be used in
establishing a major lineage of Euascomycetes with perithecial
ascocarps.
Key words: Ascomycetes, Devonian, fungi, Rhynie chert