Early Famennian bryozoan fauna from the Baqer-abad section, northeast Isfahan, central Iran
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ORIGINAL PAPER
Early Famennian bryozoan fauna from the Baqer-abad section, northeast Isfahan, central Iran Andrej Ernst 1
&
Ali Bahrami 2 & Ayesheh Parast 2
Received: 15 April 2019 / Revised: 2 July 2019 / Accepted: 16 January 2020 # The Author(s) 2020
Abstract A bryozoan fauna from the Upper Devonian (lower Famennian) of the Bahram Formation of the Baqer-abad section in central Iran contains four species: three trepostomes and one rhabdomesine cryptostome. Two trepostome species and one genus are new: Anomalotoechus parvus sp. nov. and Zefrehopora asynithis gen. nov. et sp. nov. The trepostome Coeloclemis zefrehensis Ernst et al., 2017 and the rhabdomesine cryptostome Euthyrhombopora tenuis Ernst et al., 2017 were recorded previously from the Upper Devonian (Frasnian) of the Bahram Formation at the Zefreh section. The fauna is dominated by the erect ramose Euthyrhombopora tenuis, accompanied by relatively frequent Zefrehopora asynithis, which developed both the erect and encrusting colonies. The bryozoans indicate low to moderate water energy environment in a middle to outer ramp position. Low diversity and high abundance of one species indicate an environmental stress apparently caused by strong sediment deposition. No significant differences in the composition of the bryozoan assemblages of the Frasnian and lower Famennian of the Bahram Formation were observed mirroring global patterns. Keywords Bryozoa . Taxonomy . Early Famennian . Northeast Isfahan . Central Iran
Introduction The late Middle and Late Devonian represents a relatively warm period with an acme in diversity, size and latitudinal distribution of reefs and associated shallow-water sediments in the Middle Devonian (Flügel and Kiessling 2002; Joachimski et al. 2009). On the other hand, the midPalaeozoic underwent dramatic change in Earth’s climate This article is registered in Zoobank under urn:lsid:zoobank.org:pub:DAD5D022-364E-4E12-938EFC2434767ABC * Ali Bahrami [email protected] Andrej Ernst [email protected] Ayesheh Parast [email protected] 1
Institut für Geologie, Universität Hamburg, 20146 Hamburg, Germany
2
Department of Geology, Faculty of Sciences, University of Isfahan, Isfahan, Iran
systems which resulted in changes in ocean chemistry and sea level. As a consequence of this, palaeoecosystems were impacted by several mass extinctions and ecological perturbations spanning millions of years (e.g. Talent et al. 1993). Fluctuations in physical palaeoenvironments and resultant mass extinctions were recorded in the sedimentological record by lithological changes and geochemical excursions which are also dependent on the depositional setting (Mottequin et al. 2017). Middle to Late Devonian strata are mainly composed of shallow-water facies and occur in isolated units in central Iran (e.g. Zahedi 1973; Soffel and Förster 1984; Wendt et al. 2005). The distribution of the upper Palaeozoic sediments around Isfahan (Fig. 1) is mostly limited to the northern Isfahan basin (Soh and Natanz regions Najhf, Negheleh, Varkamar, Northe
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