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The Upper Tremadocian (Ordovician) graptolite Bryograptus: taxonomy, biostratigraphy and biogeography |
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| Authors: | by JÖRG MALETZ SVEN EGENHOFF† RICARDO ALONSO‡ |
| Institution: | Department of Earth Sciences, St Francis Xavier University, Antigonish, Nova Scotia, Canada;e-mail; Department of Geosciences, Colorado State University, 322 Natural Resources Building, Fort Collins, CO 80523-1482, USA;e-mail; Universidad Nacional de Salta, Facultad de Ciencias Naturales, Buenos Aires 177, 4400 Salta, Argentina;e-mail |
| Abstract: | Abstract: The taxonomy, biostratigraphical and palaeogeographical distribution of the Lower Ordovician graptolite genus Bryograptus is evaluated. Bryograptus is recognized as a distinct triradiate anisograptid with a multiramous, pendent rhabdosome. The species of the genus Bryograptus can be interpreted as shallow water faunal elements with a strongly limited biogeographical distribution to the Atlantic Faunal Realm. Bryograptus is restricted to a narrow interval in the Upper Tremadocian, the Bryograptus Biozone of Scandinavia and South America (Argentina), making it a taxon with a high potential for precise biostratigraphical correlations. The proximal end development can be used to differentiate the genus Bryograptus from other pendent multiramous graptoloid genera with a homoplastic rhabdosome development. Characteristics of the proximal end development and structure easily differentiate these genera in relief specimens, but not in flattened material. |
| Keywords: | Ordovician graptolites taxonomy biostratigraphy Baltica South America Argentina Bryograptus |