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.)

Abstract

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 ...

Conodont biostratigraphy of the Nalai section (Guangxi) and new data on the age of the Zdimir beds in South China.

“…In addition to Dale section in the Xianzhou area, the T assemblage was only reported in the Luzhai and Wuxuan (Yu et al 1979, p. 99;Yu & Kuang 1982, p. 46), both of which are geographically close (approximately ninety kilometres, respectively) to the Dale section. According to Wang (1979), the conodont Polygnathus declinatus, a species initially thought to be transitional between P. inversus and P. serotinus by Wang (1979) but viewed as a junior synonym of P. serotinus by Klapper & Vodrážková (2013) and present paper, was reported from the uppermost part of the Shipeng Member to the lowermost part of the Liuhui Member of the Sipai Formation. In addition, P. serotinus together with P. inversus and Nowakia holynensis was also obtained by Bai et al (1982, p. 14) and Bai et al (1994, p. 142) from the middle part of the Liuhui Member at the Dale section.…”

“…Later, the alpha or early morphotype of Lane & Ormiston (1979) was formally termed P. pseudoserotinus by Mawson (1987a), and P. serotinus was only restricted to the beta and gamma morphotypes of Lane & Ormiston (1979). However, Klapper & Vodrážková (2013) treated some supposedly transitional forms between P. inversus and P. serotinus (Klapper & Johnson 1975, pl. 3, figs 19-22, 24-31;Uyeno & Klapper 1980, pl.…”

“…Accordingly, P. pseudoserotinus is accepted as a junior synonym of P. serotinus herein. Klapper & Vodrážková (2013) also made a detailed morphological analysis of Polygnathus serotinus and recognized three informal morphotypes of this species based on the outline of the shelf-like protuberance on the outer side of the pit. In the present paper, morphotype 1 ( Figs 8N, 9E, K, M, O) and morphotype 2 (Figs 8O, 9C, G, I) of Klapper & Vodrážková (2013) are both collected, whereas one juvenile specimen ( Fig.…”

“…Klapper & Vodrážková (2013) also made a detailed morphological analysis of Polygnathus serotinus and recognized three informal morphotypes of this species based on the outline of the shelf-like protuberance on the outer side of the pit. In the present paper, morphotype 1 ( Figs 8N, 9E, K, M, O) and morphotype 2 (Figs 8O, 9C, G, I) of Klapper & Vodrážková (2013) are both collected, whereas one juvenile specimen ( Fig. 9B) with an incipient shelf-like bulge on the outer side of the pit extending farther to the posterior end corresponds to morphotype 3 of Klapper & Vodrážková (2013).…”

“…-Polygnathus linguiformis bultyncki ranges from the serotinus Zone to costatus Zone (Klapper & Vodrážková 2013).…”