Bryozoans from the Jurginskaya Formation (Famennian, Upper Devonian) of the Tom-Kolyvansk area (Western Siberia, Russia)

Zoya Tolokonnikova Geologos, 2010, 16 (3): 139–152 doi: 10.2478/v10118-009-0009-7 Bryozoans from the Jurginskaya Formation (Famennian, Upper Devonian) of the Tom-Kolyvansk area (Western Siberia, Russia) Zoya Tolokonnikova Kuzbass State Pedagogical Academy, Kuznetsov Str. 6, 654041 Novokuznetsk, Russia; e-mail: Abstract Nine bryozoan species are described from the Jurginskaya Formation (Famennian, Late Devonian) from Western Siberia, Russia, namely: Leptotrypella pojarkovi Orlovski, 1961, Rhombopora subtilis Nekhoroshev, 1977, Klaucena lalolamina Yang, Hu, Xia, 1988, Eofistulotrypa famennensis sp. n., Atactotoechus cellatus sp. n., Nikiforopora jurgensis sp. n., Eridotrypella tyzhnovi sp. n., Mediapora elegans sp. n., and Klaucena gracilis sp. n. The studied assemblage shows palaeogeographical affinity with Kazakhstan, Kirgizia, Transcaucasia, China, and the United States of America. Keywords: Bryozoa, Late Devonian, Western Siberia, Russia Introduction The sedimentary Jurginskaya Formation spreads on the eastern periphery of the TomKolyvansk area (south of Western Siberia, Russia). The age of the formation is Middle-Late Famennian, based on stratigraphy, lithology and fossils (Kraevskaya, 1960; Babin et al., 1999; Gutak & Tolokonnikova, 2010). The first bryozoan fauna was discovered in the 1940s, but without a detailed description (Kraevskaya, 1960). Bryozoans outnumber the other fossils (brachiopods, crinoids, cephalopods, bivalves). The bryozoan assemblage consists of cystoporates (Eofistulotrypa famennensis sp. n.), trepostomes (the already known species Leptotrypella pojarkovi Orlovski, 1961, and three new species: Atactotoechus cellatus sp. n., Nikiforopora jurgensis sp. n., Eridotrypella tyzhnovi sp. n.), as well as rhabdomesines (two already known species Rhombopora subtilis Nekhoroshev, 1977, and Klaucena lalolamina Yang, Hu, Xia, 1988; and two new species: Mediapora elegans sp. n., and Klaucena gracilis sp. n.). Methods and material The material for the present study was collected during the summer of 2008 in the type section of the Jurginskaya Formation on the right bank of the Tom River near the town of Jurga in the Kemerovo region (Fig. 1). The bryozoans were found at three localities, mainly in shales, rarely in calcareous sandstones and siliceous limestones. They were investigated in thin section using a binocular microscope. A total of 103 thin sections were studied. The morphological terminology is adopted from Astrova (1978) and Boardman et al. (1983). The taxonomic descriptions of the bryozoan fauna are based on measurements of the Bryozoans from the Jurginskaya Formation (Famennian, Upper Devonian) of the Tom-Kolyvansk area... 140 Zoya Tolokonnikova Fig. 1. Scheme of spreading of deposits of the Jurginskaya Formation (compiled on unpublished data of Tyzhnov, 1943). morphological characteristics. The inner diameter was measured for hollow characteristics such as apertures and autozooecial chambers. The spacing of the morphological characteristics at the colony surface was measured from the centre to the next centre of the apertures. Additional quantitative characteristics studied are the number of exilazooecia and the acanthostyles surrounding each autozooecial aperture. The spacing of the horizontal structures such as diaphragms was quantified by counting their number in 1 mm of the length of the host autozooecium. Numerical statistical values (mean, standard deviation, variation coefficient, and minimum/maximum values) were calculated following Köhler et al. (1996). The described material is stored at the Kuzbass State Pedagogical Academy (Novokuznetsk, Russia; collection number 4). Systematic palaeontology Phylum Bryozoa Ehrenberg, 1831 Class Stenolaemata Borg, 1926 Order Cystoporata Astrova, 1964 Suborder Fistuliporina Astrova, 1964 Family Fistuliporidae Ulrich, 1882 Genus Eofistulotrypa Morozova, 1959 Type species: Eofistulotrypa manifesta Morozova, 1959, Frasnian (Late Devonian), Kuzbass (Russia). Diagnosis: colonies ramose. Autozooecia with diaphragms. Apertures circular-oval, possessing well-developed lunaria. Vesicles in exozone only. Occurrence: China, Russia, Mongolia; MiddleLate Devonian. Discussion: Eofistulotrypa Morozova, 1959 differs from Fistulotrypa Bassler, 1929 in the absence of vesicular tissue in the endozone. Eofistulotrypa famennensis sp. nov. (Figs. 2 A–C; Table 1) Etymology: referring to the Famennian in which this species was found. Holotype: 4/18.1; paratype: 4/18.2. Type locality: Tom River, Kemerovo region, Russia. Type horizon: Jurginskaya Formation, Podonino horizon, Middle-Late Famennian (Late Devonian). Diagnosis: colonies ramose with self-incrustation. Apertures circular, large; lunaria weakly developed. Vesicles 2–3 rows, developed in exozones only. Description: colonies are ramose with secondary overgrowth. Branches 10–18 mm in diameter, secondary overgrowths 5–7 mm thick. Endozones 4–5 mm wide, exozones 3–6 mm wide. Autozooecial walls 0.012 mm thick in endozones, 0.025 mm thick in exozones. Autozooecial diaphragms straight or inclined, numbering 1–2 on 1 mm of autozooecial length in endozones and 3–5 on 1 mm in exozones. Au- Bryozoans from the Jurginskaya Formation (Famennian, Upper Devonian) of the Tom-Kolyvansk area... 141 Table 1. Descriptive statistics for Eofistulotrypa famennensis sp. nov. Eofistulotrypa famennensis sp. nov. N X SD aperture width [mm] 20 0.30 aperture spacing from centre to centre [mm] 15 0.45 lunaria length [mm] 10 lunaria width [mm] CV MIN MAX 0.029 9.70 0.270 0.37 0.065 14.47 0.350 0.57 0.03 0.012 37.10 0.025 0.05 10 0.09 0.018 20.60 0.075 0.12 vesicles per 1 mm] 10 2.35 0.337 14.36 2.000 3.00 diameter of vesicles [mm] 10 0.17 0.036 20.30 0.120 0.25 Abbreviations: N = number of measurements, X = mean, SD = standard deviation, CV = coefficient of variation, MIN = minimal value, MAX = maximal value. tozooecial apertures circular. Lunaria weakly developed, 0.025 mm thick in the middle part. Vesicles large, abundant, arranged in 2–3 rows, rarely in 5 rows between autozooecia, polygonal in tangential section. Discussion: Eofistulotrypa famennensis sp. nov. is similar to Eofistulipora primacylindilla Xia, 1997 from the Famennian of Xinijang, China (crepida Conodont Zone), but differs in colony form (ramose with secondary overgrowth versus ramose with central zooecia in Eofistulipora primacylindilla). The apertures are circular and the width of 0.27–0.37 mm in Eofistulotrypa famennensis is different in Eofistulipora primacylindilla, which shows an oval shape of 0.14–0.2 mm in width and 0.23–0.28 mm in length. Order Trepostomata Ulrich, 1882 Suborder Amplexoporina Astrova, 1965 Family Atactotoechidae Duncan, 1939 Genus: Atactotoechus Duncan, 1939 Type species: Atactotoechus typicus Duncan, 1939, Traverse Group (Middle Devonian), United States of America. Diagnosis: colonies encrusting, massive or branched. Autozooecia with polyg (...truncated)