ABSTRACT:Klapper, G. and Vodrážková, S. 2013. Ontogenetic and intraspecific variation in the late Emsian -Eifelian (Devonian) conodonts Polygnathus serotinus and P. bultyncki in the Prague Basin (Czech Republic) and Nevada (western U.S.). Acta Geologica Polonica, 63 (2), 153-174, Warszawa. Telford 1975 and P. bultyncki Weddige 1977 from the Prague Basin and Nevada display normal variation for Devonian conodont species. A considerable number of previous authors, however, have proposed unnecessary synonyms of these two species, primarily because they have not recognized ontogenetic variation. In contrast, we interpret the variation as ontogenetic as well as intraspecific and present detailed synonymies as a result. A third species, P. praetrigonicus Bardashev 1992, which has been carried in open nomenclature for many years, is an important indicator of the basal costatus Zone in the Prague Basin, New York, and Nevada. We review the stratigraphic distribution of these three species and the conodont zonation across the Emsian-Eifelian (Lower-Middle Devonian) boundary. Polygnathus pseudocostatus sp. nov. (partitus-costatus zones, central Nevada) is described herein. We have observed a decrease in the pit size during ontogeny in P. bultyncki although we have not measured enough specimens to rule out intraspecific versus ontogenetic variation. Samples from populations of Polygnathus serotinusKey Words: Devonian; Emsian-Eifelian conodont zonation; Ontogenetic and intraspecific variation; Taxonomic revision.Acta Geologica Polonica, Vol. 63 (2013), No. 2, pp. 153-174 DOI: 10.2478/agp-2013 Brought to you by | MIT Libraries Authenticated Download Date | 5/10/18 9:06 AM 154 GILBERT KLAPPER AND STANISLAVA VODRÁŽKOVÁ Clark 1967;Sandberg and Ziegler 1973;Dzik 2002Dzik , 2006Miller 2007). The reason for this may be that a microfossil collection is not always encountered from which an ontogenetic series can be reconstructed based on specimens that each represent a single growth stage. It is thus not surprising that supposedly new conodont species have been proposed by authors who have not taken ontogenetic variation into consideration.On the subject of ontogeny in an overview of palaeontological taxonomy, Forey et al. (2004, p. 645) wrote: "Palaeontologists, in general, are hampered by the lack of knowledge of ontogenetic variation. Growth stages of individual taxa have received separate names, which may spuriously increase apparent diversity." . . "but the problem is far more acute in the fossil record and can only be solved by fortuitous finds." However, study of micropalaeontological collections that yield either a single species of one genus or just two species of distinctly different morphology may potentially allow more frequent reconstruction of ontogenetic series than is generally possible with macrofossils. That is, we are referring to those macrofossils in which single specimens do not preserve the record of ontogeny, as opposed, for example, to single specimens of ammonoids which may do so.In his general paper on ...

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Taxonomic composition and stratigraphic distribution of lingulate brachiopod taxa around the Emsian/Eifelian boundary of the Prague Basin were examined. Twelve species have been determined and the presence of others is suggested. The prevalence of micromorphic biernatids, Havlicekion and Opsiconidion, in all the studied samples is significant. A mode of life for biernatids, especially from the genus Opsiconidion, is discussed. A new Devonian occurrence of the siphonotretid Orbaspina is recorded. Lingulate brachiopods do not display any significant change around the Emsian/Eifelian boundary or at the Basal Choteč Event (Middle Devonian, Eifelian, costatus Zone) and thus confirm the general uniformity of lingulate faunas in the Lower and early Middle Devonian.•

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