Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155 Contents lists available at ScienceDirect Palaeogeography, Palaeoclimatology, Palaeoecology journal homepage: www.elsevier.com/locate/palaeo Initial plant diversification and dispersal event in upper Silurian of the Prague Basin T ⁎ Petr Krafta, , Josef Pšeničkab, Jakub Sakalaa,Jiří Frýdac,d a Institute of Geology and Palaeontology, Faculty of Science, Charles University, Albertov 6, 128 43 Praha 2, Czech Republic b Centre of Palaeobiodiversity, West Bohemian Museum in Plzeň, Kopeckého sady 2, 301 00 Plzeň, Czech Republic c Faculty of Environmental Sciences, Czech University of Life Sciences Prague, Kamýcká 129, 165 21 Praha 6-Suchdol, Czech Republic d Czech Geological Survey, Klárov 3/131, 118 21 Prague 1, Czech Republic ARTICLE INFO ABSTRACT Keywords: A relatively rich association of six species of embryophyte plants is known from the upper Silurian of the Prague Přídolí Basin (Bohemian Massif, Czech Republic). All stratigraphically controlled specimens come from the Terrestrialization Neocolonograptus parultimus-Neocolonograptus ultimus Zone of the Přídolí. A new genus and species, Tichavekia Volcanic islands grandis Pšenička, Sakala et Kraft, is established. The new combination Aberlemnia bohemica (Schweitzer) Sakala, Habitat Pšenička et Kraft, comb. nov. illustrates its Lycophytina affinity. The distribution and taphonomy of these plants Climate in the Prague Basin indicates the proximity of exposed land interpreted to be islands of volcanic origin. Two local Sea level associations show primary differences in vegetated areas of the islands and apparent ecological responses of the primitive vascular plants to their habitats. Suitable environments in the coastal zones of volcanic islands in the Prague Basin, which was situated at the outer periphery of a broad Gondwanan shelf, likely represent significant transfer points for an initial dispersion and a first expansion of land plants. Repeated vegetation of the islands is inferred from the discrete distribution of land plants at different stratigraphic levels. These changes are ex- plained partly in context of local changes of the island relief, and partly as responses to global climatic and sea level fluctuations, and fit environmental dynamics of islands of volcanic origin in general. This Initial Plant Diversification and Dispersal Event (IPDDE) is of considerable significance in the evolution of plants documented from the Bohemian Massif. 1. Introduction missing. Tracing early plant evolution is often focused on individual taxa, The search for the oldest land plant (embryophyte) reflects an effort their taxonomy, appearances and stratigraphic ranges. Cooksonia, the to prove a substantial step of terrestrialization. It is of importance for early or even primordial land plant, apparently played a key role: it has molecular biologists and (neo)botanists to calibrate the molecular clock been described from a number of regions, ranges widely from the and establish a starting point for phylogenetic studies of early vascular Silurian to the early Devonian, and is represented by several species plants (e.g. Clarke et al., 2011; Kenrick et al., 2012; Gerrienne et al., such as C. pertoni, C. paranensis, C. banksii, and doubtfully C. cambrensis, 2016). The first appearance of such plants, based on macroscopic evi- C. hemisphaerica (Gonez and Gerrienne, 2010a) with many other spe- dence, can be provisionally considered to have occurred in the Late cimens having been described in open nomenclature. Cooksonia also Ordovician in Poland (Salamon et al., 2018). However, the earliest occupies a special position in the colonization of terrestrial habitats, unequivocal record based on Cooksonia (the oldest accepted macrofossil which is a major aspect of early plant research based on broad studies of land plant) from almost coeval sites in Ireland (Edwards et al., 1983) associations, their successions and distributions (e.g. Edwards and and Bohemia (Libertín et al., 2003, 2018), points to the appearance of Wellman, 2001; Kenrick et al., 2012). This complex paleoecological land plants in the Wenlock. On the other hand, fossil spores and isolated approach has attracted considerable attention over the past two dec- sporangia indicate a much older appearance of embryophytes, probably ades. as early as in the Middle Ordovician (Clarke et al., 2011; Gerrienne Sporadic occurrences in the early Silurian are followed by still in- et al., 2016; Vavrdová, 1984), even if a coeval macrofossil record is frequent and very low diversified vascular plants recorded globally ⁎ Corresponding author. E-mail addresses: [email protected] (P. Kraft), [email protected] (J. Pšenička), [email protected] (J. Sakala), [email protected] (J. Frýda). https://doi.org/10.1016/j.palaeo.2018.09.034 Received 16 April 2018; Received in revised form 25 September 2018; Accepted 26 September 2018 Available online 09 October 2018 0031-0182/ © 2018 Elsevier B.V. All rights reserved. P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155 from the Ludlow (Edwards and Wellman, 2001, tab. 2.1; Edwards and simply called Barrandian or neutrally labeled as Barrandian area). Its Richardson, 2004, tab. 1; Wellman et al., 2013, tab. 29.1). The present geotectonic origin is still a matter of discussion as to whether the paper is focused on the first significant diversification and dispersal Barrandian formed a part of accreted peri-Gondwanan terranes episode of the vascular plants in the Přídolí (e.g., Obrhel, 1962; Kotyk (Stampfli et al., 2002, 2013) or whether it was a small isolated crustal et al., 2002; Kraft and Kvaček, 2017). As we consider it to be one of the block (microcontinent or terrane) often referred to as Perunica key steps in global terrestrialization, we introduce the term Initial Plant (Havlíček et al., 1994; Cocks and Torsvik, 2002; Franke et al., 2017). Diversification and Dispersal Event (IPDDE). This event is well-docu- Whatever its origin, its paleogeographic position at the outer Gond- mented in several paleoregions such as Avalonia, Laurentia, Baltica, wanan shelf is widely agreed (e.g. Scotese, 2001; Servais and Sintubin, Gondwana, South and North China and Kazakhstania (Edwards and 2009; Stampfli et al., 2013; von Raumer et al., 2015). Wellman, 2001, fig. 2.7; Wellman et al., 2013, fig. 29.4) representing Silurian rocks of the Prague Basin comprise mainly black graptolitic wide paleolatitude and paleoclimatic ranges. shale prevailing in the lower part of succession, carbonates forming the Our study of the material discovered in the Prague Basin represents main portion of the upper part, and volcanic rocks related to several an important piece of the puzzle for analysis of the settings which volcanic centres. The facies distribution indicates that shallow water caused this event. Suitable water-land, freshwater-marine water inter- deposits were surrounded by deeper and open marine settings domi- faces on shores, pattern of ocean currents, humid microclimates on nated by hemi-pelagic sedimentation. The volcanic rocks represent terrestrial habitats and other factors were present in several basic set- within-plate, transitional alkali to tholeiitic basalts, which erupted in a tings: along stable coasts of continents, along mobile zones such as continental rift setting through the thick Cadomian crust of the uplifting orogens with dynamic development of coasts and related en- Teplá–Barrandian Unit (Tasáryová et al., 2018). vironments and, finally, around islands. The principal locality Kosov is situated on Kosov Hill south of The remains of the fossil plants from the Přídolí are quite rare in the Beroun in central Bohemia (Fig. 1). It is a classical fossil site of the Prague Basin with the exception of the locality Kosov near Beroun Silurian in the Prague Basin (for details on the Bohemian Silurian see (Fig. 1). Our study is based on relatively common, recently collected Kříž, 1991, 1992, 1998). Note that the name Kosov has been used since material from this site and its vicinity, supplemented with sparse the first half of the 19th century for several different outcrops and published data on other localities in the Basin. sections on its slopes spanning a wide stratigraphic range from the Upper Ordovician to upper Silurian. Our material was collected in the 2. Locality, geological and paleontological settings large quarry in the northwestern side of the Kosov Hill (Velký Kosov; 451 m elevation point) near Jarov (part of Beroun). The quarry was ř ž ř The sedimentary record of Silurian strata of the Prague Basin described in detail by K í (1992). The P ídolí is exposed in the eastern (Havlíček, 1981) represents only a small part of the system of Paleozoic part of the quarry. Fossils of land plants were discovered in the basins (Fig. 1). Those basins formed on the Proterozoic basement re- northeastern part, ~200 m north of the main gate to the quarry, ř ž present younger tectono-stratigraphic components of the crustal block ~100 m southeast of the section no. 356 (the section described by K í , called the Teplá-Barrandian Unit (also considered as terrane, sometimes 1992). The plant remains were collected in loose blocks accumulated Fig. 1. A – Sketch map with the location of the Silurian of the Prague Basin situated in the central part of the Czech Republic (small area southwest of Prague) and in the Bohemian Massif (yellow shaded). B – Simplified detail of the central part of the Prague Basin with extent of the Silurian. The localities mentioned