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Acta Musei Nationalis Pragae, Series B, Historia Naturalis, 62 (1–2): 1–70 issued June 2006 Sborník Národního muzea, Serie B, Přírodní vědy, 62 (1–2): 1–70 TREMADOCIAN TRILOBITES OF THE PRAGUE BASIN, CZECH REPUBLIC MICHAL MERGL Department of Biology, University of West Bohemia, Klatovská 51, 306 19, Plzeň, Czech Republic; e-mail: [email protected] Mergl, M. (2006): Tremadocian Trilobites of the Prague Basin, Czech Republic. – Acta Mus. Nat. Pragae, Ser. B, Hist. Nat., 62 (1–2): 1–70. Praha. ISSN 0036-5343. Abstract: A revision of the trilobites of the Třenice and Mílina Formations (Upper Tremadocian) confi rms the presence of 29 species. Celdometopus gen. n. is established, and six new species, Agerina clymene, Hemibarrandia klouceki, Holoubkochei- lus asopus, Parabathycheilus krafti, Platypeltoides perseis, and Pricyclopyge oceanitis are described. All formerly described species of the genera Geragnostus, Ottenbyaspis, Hemibarrandia, Holoubkovia, Anacheirurus, Parapilekia, Parabathyche- ilus, Holoubkocheilus, Proteuloma, Harpides, Holubaspis, Dikelokephalina, Ceratopyge, Niobina, Apatokephalus, Celdo- metopus, and Eulomina, are re-described or further commented on. Old and new data about their morphology, distribution, and affi nity are summarized. The fauna contains numerous cosmopolitan taxa, but most of the species show Gondwanan affi nity, especially among calymenaceans and by the presence of an early cyclopygid. Compared with other regions, the total absence of olenid trilobites is characteristic. A high taxonomic diversity with dominant cheirurids and illaenids makes this one of the richest late Tremadocian trilobite faunas ever described. ■ Trilobita, taxonomy, Tremadocian, Ordovician, Barrandian area, Prague Basin, Bohemia, Czech Republic. Received January 30, 2006 Introduction phical framework. The horizon and locality at which a uni- que and nearly complete specimen of this species was found The fi rst report of the Tremadocian trilobites from the is not precisely known. The specimen, sometimes called the Barrandian area was written by Celda Klouček in the year rarest trilobite of Bohemia (Prantl 1945), was found in the 1914. However, a unique specimen of Harpiges grimmi iron ores at Holoubkov iron works in or around 1840, and its BARRANDE, 1872 had been known since the mid nine- exact locality has remained unknown since the fi rst report. teenth century. The Bohemian Tremadocian trilobites have The suggestions of locating the site near Dobřív (Krejčí been described by many authors (Růžička 1926, 1931, 1877) or Mirošov (Purkyně 1914, Prantl 1945) are probably Klouček 1931, Vaněk 1965, Pek 1977, Mergl 1984a, 1994), incorrect. Uncertainty about the locality led to speculations but some species were established on poorly preserved or that the species is of younger Arenig age (Barrande 1872). too few specimens. They have not been properly studied, In August 1914, Professor Celda Klouček found the and are sometimes described as being insuffi ciently known remains of trilobites in the reddish chert cobblestones by other authors (Moore 1959, Peng 1990, Fortey and of a road near Hořovice. After a short search he found Owens 1991, Ebbestad 1999). the original trilobite-bearing bed at a local quarry at the Most of the newly studied material was collected during Olešná village near Komárov in the SW part of the Prague the past twenty years at the classical and new localities. Basin. This bed is situated in the upper part of the Mílina Earlier authors (Klouček 1917, 1925, 1926a, Koliha 1937, Formation, and its lithology and petrography have been Růžička 1926, 1931) noted the remarkably high diversity described in detail by Kettner (1916). Until Klouček’s fi nd, of the trilobite fauna in the known localities. The main pur- the fauna of the reddish cherts was considered to be very pose of the present research is to utilize small fragments and poor, consisting only of linguliform brachiopods, sponges, morphologically less attractive exoskeletal parts (librigenae, and an orthid Jivinella incola. In 1917, Klouček listed doublures, smooth fragments, and thoracic segments). In eleven trilobite species, with only approximate generic this way, the author attempt to reveal the morphology of attributions. Modifi ed versions of this list of trilobite taxa hitherto unknown but taxonomically signifi cant exoskele- were repeatedly published in the following years (Koliha tal parts. The results enable a better reconstruction of the 1924, 1937, Klouček 1926a). In 1920, Klouček found a si- species. Furthermore, the new evaluation of the remarkably milar trilobite fauna in the Úvaly east of Prague. From this rich Tremadocian trilobite of the Prague Basin fauna might region he reported fi fteen trilobite species (Klouček 1922), bring some new views to the evolutionary history of benthic among which occurred Harpides cf. rugosus. In 1924, a pri- faunas in the southwest periphery of Gondwana in the early vate collector named Vojtěch Kraft, together with Klouček, Ordovician. discovered a diverse but very fragmental trilobite fauna in Historical overview the dumps of the abandoned “V Ouzkém” iron ore mine near Holoubkov. Klouček (1925) suggested the same age of Harpides grimmi BARRANDE, 1872 is the earliest the trilobite fauna, but the haematite in which these fossils known trilobite of Tremadocian age in the present stratigra- occur has recently been referred to the subjacent Třenice 1 Formation. Klouček (1925) listed thirteen trilobite species in the known localities since the 1930s. The fi nd of the tri- from the Mílina Formation. However, only one species was lobite Bavarilla cf. hofensis at Popovice near Brandýs, east diagrammatically fi gured by the author (Klouček 1926b), of Prague, was briefl y commented on by Vaněk (1999), but and another trilobite fragment from Holoubkov was fi gured this specimen was not accessible to the present author. without any formal description (Klouček 1931). According their manuscripts and short notes, Klouček and Jan Koliha Geological setting intended to publish a trilobite monograph based on their The early Ordovician sedimentation in the Prague Basin own fi ndings from the years 1914 to 1931 (Klouček and started by the deposition of coarse grained siliciclastics in Koliha 1927, Klouček 1931). However, the preparation of a narrow, tectonically based trench extending from Roky- this work was halted by Klouček’s death in 1935. cany in the SW to the Úvaly in the NE (Text-fi gs. 1, 2). The In the meantime, a private collector named R. Růžička transgression of the basal Třenice Formation overlies an (1926) had published a study of trilobites collected at the uneven surface formed by Precambrian or Cambrian rock. “V Ouzkém” locality near Holoubkov. He reported 21 spe- The Třenice Formation is comprised of coarse- to medium- cies. Eight of them he described as new, but his determina- -grained sandstones (lithic greywackes and arkoses) and, at tion and illustrations were of poor quality. This paper was its base, by petromictic conglomerates of a local proveni- immediately criticised by Klouček and Koliha (1927), and ence. Eroded Upper Cambrian volcanics surrounding the was followed by a short reply from Růžička (1928). Five years basin were the main source of rhyolite and andesite clasts later, Růžička (1931) published another short paper descri- in the sandstones. Local haematite impregnations in conglo- bing additional fi nds from the “V Ouzkém” locality with the merates and sandstones are common. On the contrary, thin formal description of one new species. Two more short pa- lenticular haematitic beds, often quartzitic and associated pers by Růžička (1935, 1941) dealt with the trilobites from with stromatolitic structures, are very local. The thickness the Olešná locality of the overlying Mílina Formation. of the Třenice Formation ranges from 0 to 30 m, and rarely After the Second World War, the investigation of the up to 70 m (Havlíček 1998). Tremadocian trilobite fauna produced only short reports The overlying Mílina Formation has comparatively based on old material collected between the wars. The sys- smaller extent, and has been considered to be of a regres- tematics, nomenclature, and morphology of selected taxa sive character by many authors (Kettner 1921, Bouček 1947, were reviewed by several authors (Prantl and Přibyl 1947, Havlíček and Šnajdr 1956). However, the Mílina Formation 1949a, Přibyl 1950, 1953, Vaněk 1959). Kalat (1949) briefl y in the Komárov area rests on Upper Cambrian volcanics, reported the discovery of a new trilobite locality in Úvaly thus having rather a transgressive than regressive charac- east of Prague. In the mid-1960s, Vaněk published a short ter. For the formation pink, red-brown, and grey chert beds paper and a larger trilobite monograph of the Tremadocian intercalated with fi ne red-brown greywackes and thin inter- trilobites of Central Bohemia (Vaněk 1964, 1965). This beds of silty shales are typical. The facies development of monograph is the fi rst complete review of the trilobites of the Mílina Formation in the Úvaly area is characteristic by the Třenice and Mílina Formations. Subsequently, Havlí- fi ne-grained sandstones and quartzitic shales. The thickness ček and Vaněk (1966) reviewed the results. Vaněk (1965) of the formation ranges from 0 to 30 m (Havlíček 1998). reported 23 trilobite species, mostly based on the material collected by the previous authors and collectors. However, the validity of Vaněk’s taxonomic determination has to be considered as somewhat questionable. For example,