The Earliest Ostracods from the Ordovician of the Prague Basin, Czech Republic
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DE DE GRUYTER Acta Geologica Polonica, Vol. 64 (2014), No. 4, pp. 367–392 OPEN DOI: 10.2478/agp-2014-0021 G The earliest ostracods from the Ordovician of the Prague Basin, Czech Republic KAROLÍNA LAJBLOVÁ AND PETR KRAFT Institute of Geology and Palaeontology, Charles University, Albertov 6, 128 43 Praha 2, Czech Republic. E-mails: [email protected], [email protected] ABSTRACT: Lajblová, K. and Kraft, P. 2014. The earliest ostracods from the Ordovician of the Prague Basin, Czech Republic. Acta Geologica Polonica, 64 (4), 367–392. Warszawa. The earliest ostracods from the Bohemian Massif (Central European Variscides) have been recorded from the Middle Ordovician of the Prague Basin (Barrandian area), in the upper Klabava Formation, and became an abundant component of fossil assemblages in the overlying Šárka Formation. Both early ostracod associations consist of eight species in total, representing mainly eridostracans, palaeocopids, and binodicopids. The revision, description, or redescription of all species and their distribution in the basin is provided. Their diversification patterns and palaeogeographical relationships to ostracod assemblages from other regions are discussed. Key words: Ostracoda; Middle Ordovician; Barrandian area; Prague Basin; Taxonomy; Palaeobiogeography. INTRODUCTION to middle Middle Ordovician. The oldest ostracods appear rarely in the volcanosedimentary Ejpovice Ostracods belong to the most abundant arthro- Member at the top of the Klabava Formation, dated pods, with their fossil record extending back to the as late Dapingian. They started to be common in the Early Ordovician. They represent one of the most overlying Šárka Formation, of latest Arenigian to successful crustacean groups. They first appeared in Oretanian age (early to middle Darriwilian; Text-fig. 2) the middle Tremadocian of Baltica, represented by (e.g. Budil et al. 2007; Polechová 2013), although the genus Nanopsis (Tinn and Meidla 2004). The di- their species diversity was still low, at least as com- versity of ostracods started to grow distinctly during pared to Baltica (Tinn and Meidla 1999, 2004; Tinn the Middle Ordovician (late Floian to Darriwilian), et al. 2006; Schallreuter 1980), Avalonia (Siveter with the peak of their Ordovician diversity reached in 2009) and Laurentia (Burr and Swain 1965; Swain the Late Ordovician (Braddy et al. 2004; Meidla 1962; Swain 1987; Landing et al. 2013). Ostracod 1996; Tinn and Meidla 2004; Williams et al. 2008). faunas of the Klabava and Šárka formations record In the sediments of the peri-Gondwanan Prague Basin the beginning of the successive increase of ostracod (Barrandian area of the Bohemian Massif; Czech Re- diversity that reached its peak in the early Katian of public; Text-fig. 1), the oldest ostracods have been the Late Ordovician (Přibyl 1979; Schallreuter and noted in the Klabava Formation (Text-fig. 2). The for- Krůta 1988). mation is up to 300 m thick and is dated as Arenigian The Prague Basin ostracods show obvious affini- (roughly Floian to Dapingian), of the middle Lower ties to ostracods from Baltoscandia (e.g. Öpik 1935; Unauthenticated Download Date | 1/13/15 10:07 AM 368 KAROLÍNA LAJBLOVÁ AND PETR KRAFT Hessland 1949; Henningsmoen 1953; Jaanusson 1957; fauna in nodules near Úvaly (Auval in the original) Schallreuter 1993; Tinn et al. 2010) and Avalonia (e.g. east of Prague, listing Cytherina prunella Barr. [= Siveter 2009), as discussed earlier by Dzik (1983) and Conchoprimitia osekensis (Přibyl, 1979)] among the Schallreuter and Krůta (1988, 1994), and commented recognised species. Barrande (1872) established two on more recent papers dealing with Early Ordovician species from the Šárka Formation: Beyrichia bo- ostracods of other regions, e.g. from Argentina (Salas hemica Barrande, 1872 (= Brephocharieis ctiradi et al. 2007; Salas 2011; Salas and Vaccari 2012) and Schallreuter and Krůta, 1988) and Primitia prunella Iran (Ghobadi Pour et al. 2011). Barrande, 1872 [= Conchoprimitia osekensis (Přibyl, The present paper provides a taxonomic revision of 1979)]. After Barrande’s (1872) descriptions, no sys- Early and Middle Ordovician ostracods from the tematic study was made for almost hundred years, al- Prague Basin, based on existing collections and on though ostracods of the Šárka Formation were listed newly acquired material. Also, it discusses their in various publications. Krejčí and Feistmantel (1885, palaeobiogeographical affinities and changes of their 1890) mentioned Beyrichia as a typical Ordovician taxonomic diversity in these early stages of their evo- fossil and this genus together with Primitia as typi- γ lution. cal of unit d1 (corresponding to the present Šárka and Dobrotivá formations combined). Wentzel (1891) compared the Barrandian Lower Palaeozoic with that HISTORY OF RESEARCH from the British Isles. He noted a possible correlation γ of unit d1 in the Barrandian area with the British The ostracods of the Klabava Formation consti- Llandeilo, based on faunal similarities, including re- tute the oldest known ostracod fauna in Bohemia. Be- spective occurrences of the ostracod species cause of their restricted occurrence confined to one Beyrichia Bohemica Barr. and Beyrichia complicata specific facies of calcareous tuffites, in which the os- Salt. It should be noted that all previously mentioned tracods are rare and often poorly preserved, they ostracods were exclusively from siliceous nodules. were first reported as late as 1980 (Krůta 1980). The first ostracods from shales of the Šárka Forma- Based on specimens visible on undissolved slabs, tion were reported by Iserle (1903) based on material Krůta (1980) recognised the following taxa: Primi- from a new locality west of Rokycany, in the slope tiella sp. A, Primitiella sp. B; ? Bythocypris sp. A, ? called “Klabavka” (Klabavská stráň nowadays). Bythocypris sp. B and Conchoprimitia sp. Dzik Among other fossils, he listed Primitia prunella (1983) isolated specimens from calcareous rewashed Barr.? as quite abundant but unfavourably preserved. tuffs (tuffites) with hydrofluoric acid and figured Holub (1908) published a revised faunal list from the two species from the same facies: Cerninella sp. n. same locality (called Drahouš by him) and mentioned and Pyxion sp. Schallreuter and Krůta (1988) revised Beyrichia bohemica Barr. and Primitia prunella Barr. Dzik’s (1983) material and used the same methods for He also reported the new locality with shales of the isolating ostracod specimens. They established sev- Šárka Formation at Kamenný Újezd near Rokycany, eral new taxa (one genus and four species): Glosso- from where he listed Primitia prunella Barr. Subse- morphites (G.) mytoensis Schallreuter and Krůta, quently, however, again most of the papers reported 1988 (= Cerninella sp. n. of Dzik 1983), Paricon- on ostracods from nodules, with notes on specimens choprimitia ventronasata Schallreuter and Krůta, from shales being exceptional. Želízko (1905) 1988, Karinutatia eoren Schallreuter and Krůta, 1988 recorded abundant Primitia bohemica Barr. (= Con- and Mytoa Schallreuter and Krůta, 1988 with Mytoa choprimitia osekensis) from the Šárka Formation; γ klabava Schallreuter and Krůta, 1988 (= Pyxion sp. Horizon D-d1 in the original, at Cekov – Cekovský of Dzik 1983), as its type species. rybník Pond. Holub (1910) mentioned abundant oc- The first ostracods from the Šárka Formation (= currence of Primitia prunella in siliceous nodules. d1 Horizon, Etage D in the original), in which ostra- Bouček (1926a) published lists of fossils from shales cods are very abundant, were mentioned by Barrande and nodules from a measured section in the brickyard (1856), who reported a new fauna from the siliceous in Praha-Vokovice. He listed two ostracods, Primitia nodules from near the town of Rokycany. He quoted prunella Barr. and Beyrichia bohemica Barr. (?). In Cytherina prunella ? Barr. (nomen nudum), the the French version of the same paper, Bouček species later formally designated based on the spec- (1926b) mentioned only the former species. Kraft imen from the Upper Ordovician (Králův Dvůr For- (1928) summarised data on fossil sites of the Osek- γ mation now, d5 Horizon of the Etage D originally). Kváň Zone (d ), which includes those belonging to Shortly afterwards, Reuss (1857) found a similar the Šárka Formation in its modern concept. He quoted Unauthenticated Download Date | 1/13/15 10:07 AM 369 EARLIEST OSTRACODS FROM THE ORDOVICIAN OF THE PRAGUE BASIN Beyrichia bohemica, Primitia prunella Barr. and Formation. Thus, the only sample with all of the Primitia transiens from nodule sites north of Roky- specimens of Dilobella grandis was found near the cany (referred to by him as cumulative locality village of Lhotka u Berouna and comes from the Do- “Osek, Díly, Rokycany”). Havlíček and Vaněk brotivá Formation and not from the Šárka Formation, (1966), in their overview of the Ordovician of the as hitherto claimed. Prague Basin, noted that ostracods were abundant in The systematic position of Cerninella complicata the Šárka Formation but were in need of revision. (Salter, 1848) remained uncertain in the revision of They listed two species, with their revised generic as- Beyrichia bohemica Barrande, 1872, the type species signment: Parapyxion prunellus (Barr.) (= Con- of Cerninella Přibyl, 1966, made by Schallreuter et choprimitia osekensis) [Parapyxion prunella in the al. (1984). This species was later redescribed by text part] and Talinella complicata (Salt.) Siveter (1985) who referred it to a new genus (= Brephocharieis