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 in text and/or in other figures are marked: 1 – Kosov Quarry and Dlouhá hora, 2 – Karlštejn, 3 – Loděnice, 4 – Koněprusy. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

145 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155 below the quarry wall, as it is impossible to collect directly in the wall Holotype. Specimen F21761b housed in WBM, figured in Fig. 2A, D; exposures for safety reasons. The plants occur in decalcified tuffaceous designated herein. shale intercalated with micritic limestone layers and lenses. The plant Isotype. Counterpart of the holotype, F21761a housed in WBM, fossils are most abundant in accumulations with graptolites, especially figured in Fig. 2B. dendroids. These fossiliferous bedding planes are apparently a mixture Type locality and horizon. Kosov Quarry; Požáry Formation, Přídolí, of fossils dwelling in a coastal environment from onshore to shallow Silurian. water rocky bottom enabling attachment of sessile dendroid graptolites. Derivation of name. Referring to its large size in comparison with Graptoloids occur also in some accumulations together with plants. most coeval plants. They confirm the Přídolian age, and the Neocolonograptus parultimus- Diagnosis. Plants up to 140 mm tall. Five times isotomously dichot- Neocolonograptus ultimus Zone (biostratigraphy used in this study ac- omized axes about 1 mm wide, with decreasing length of successive cording to Loydell, 2012; for succession of the Přídolian graptoloid dichotomy. The first dichotomy divides the plant into two asymmetrical species in the Prague Basin see Kříž et al., 1986). The typical occurrence parts. Terminal sporangia generally ~2.5 mm in diameter, sub- of vascular plants in the lower part of the Přídolí at Kosov Hill was sphaerical to ellipsod sacciform in shape, placed on the ends of the referred by Obrhel (1962, 1968), Kříž et al. (1986) and Kříž (1992). The latest extremely short dichotomies. Sporangia bear round structures shallow-water marine nature of the fossil accumulations is also sup- 0.75 to ~1 mm in diameter. Other details regarding in situ spores or ported by the presence of brachiopods (Kříž, 1992) occurring abun- conducting elements unknown. dantly on bedding planes in the blocks from the same section. It is Description. The holotype and isotype represent probably a large worth noting that remains of algae were found on number of strati- part of the original plant/sporophyte with the proximal fertile part graphic levels in the quarry section from the Wenlock to the Přídolí. represented by sporangia (Fig. 2A, B). It was at least 140 mm high, They are sometimes confused with poorly preserved vascular plants or though the basal/root part is missing. Dichotomous axes show five le- their sporangia in collections. vels (labeled A–F; Fig. 2C) of branching and are strictly isotomous. The A first detailed study of the Bohemian upper Silurian plant remains length of the branches depends on the branching level being succes- by Obrhel (1962) illustrates a concentration of plant remains in the N. sively shorter to the top. Axis width is ~1 mm, more or less constant parultimus-N. ultimus Zone at Kosov. He described a diversified asso- along branches and is smooth, lacking any cell character. The proximal ciation: Cooksonia cf. hemisphaerica Lang 1937, Cooksonia sp., ?Cook- dichotomy divided the plant into two asymmetrical parts where one sonia sp. (=Tichavekia grandis here) and indeterminate dichotomously shows one more dichotomy than the other (Fig. 2C). Terminal axes branched sterile telomes. ranges from 1.5 to 4.5 mm in length and are terminated in extremely The specimen described by Schweitzer (1980) as Cooksonia bohe- short dichotomies (Fig. 2D arrow); each axis bears one sporangium. mica is usually referred to as coming from the locality Dlouhá hora. In Two subtending pairs of such sporangia form typical groups of four. fact, Dlouhá hora is the old name for the Kosov (or Velký Kosov in some Probable conductive tissue is visible as darker colored band in the maps) Hill. It was earlier named, for example by J. Barrande (see central part of axes, close to distal short dichotomy (Fig. 2D – XB). Chlupáč , 1999), as Dlauha Hora, the same form of the name as used in Sporangia bear round structures of unknown function, which are 0.75 maps of the “Kaiserpflichtexemplar der Landkarten des stabilen Kata- to ~1 mm in diameter (Fig. 2D – XA). sters” of the village of Jarov (originally Jarow; mapped in 1840). Note Remarks. Tichavekia shows a unique combination of features: higher that J. Barrande used also the name of Kosov (or Kosow) but for a stature (up to 14 cm tall), slender axis with several successive di- different locality. The main range of the Kosov Hill (=Dlouhá hora of chotomies (up to five times) and subsphaerical to ellipsod sacciform past usage) is situated south and southwest of the Kosov Quarry. It is sporangia situated on extremely short last dichotomy. The sporangia unclear why H.-J. Schweitzer used this name (it is used also in the recall those mentioned by Obrhel (1962) and also by Edwards et al. database of the Swedish Museum of Natural History in Stockholm (1999) for their sample No. NMW96.11G.3, but the unusual character where the material is housed). We consider that the Schweitzer's spe- of the plant as a whole supports its assignment as a new genus/species. cimen was discovered on the slope of the Kosov Hill at a different place Concerning its botanical affinities, we follow the classification but close to the site with recently collected plants in northeastern edge presented recently by Gerrienne et al. (2016) in which only the pre- of the quarry. sence of a central vascular strand together with sporangia point to af- finity with Embryophytes (=land plants). In the case of the new genus 3. Systematic paleobotany the vascular strand is only inferred, based on presence of a darker-co- lored band in the central part of the axes. An axis (leafless stem) with In this chapter we describe and comment on the taxa occurring at several successive dichotomies bearing several sporangia can only be Kosov and its surroundings. The studied specimens are housed in the interpreted as being a member of Polysporangiophytes Kenrick et Crane West Bohemian Museum in Plzeň, Czech Republic with exception of the 1991. Determining whether this new fossil genus represents a member type material of Cooksonia bohemica. of ‘Protracheophytes’ or Tracheophytes is only possible based on de- The following abbreviations are used for the institutions and their tection of the nature of conducting elements. However, we did not collections: WBM – West Bohemian museum in Pilsen, CGS – Czech observe any anatomical detail as conducting elements or in situ spores. Geological Survey, Prague, NM – National Museum, Prague, SMNH – A combination of the presence of isotomous branching (successive di- Swedish Museum of Natual History, Stockholm. chotomies) and the absence of any (pseudo)monopodial branching in- Polysporangiophytes Kenrick et Crane 1991 dicates either some basal lineage of Polysporangiophytes or a member Tichavekia Pšenička, Sakala et Kraft, gen. nov. of Lycophytina sensu Kenrick and Crane, 1997, but not Euphyllophytes. Type species. Tichavekia grandis Pšenička, Sakala et Kraft, sp. nov. If we correctly interpret the terminal structures as sporangia and all Derivation of name. After František Tichávek, enthusiast and col- specimens of this taxon that are available for study as a sporophyte, an lector who discovered the type material. important question remains about the gametophyte: was it a thalloid or Diagnosis. Upright plant with at least five times isotomously bran- axial type and was it independent or interconnected with the spor- ched leafless axes. Obovate sporangia terminal, placed on very short ophyte? In this respect, there is an interesting presence of rounded axes forming a group of four sporangia. thalloid structure (see Fig. 2A) occurring on the slab close to Tichavekia. Species included. Tichavekia grandis Pšenička, Sakala et Kraft, sp. nov. It can be tentatively interpreted as both related within the same life- Tichavekia grandis Pšenička, Sakala et Kraft, sp. nov. cycle. However, to elucidate this point as well as a regular co-occur- Figs. 2A–D, 4A rence of “thalloid” structures as Nematothallus or Parka with leafless 1962 ?Cooksonia sp.; Obrhel, p. 85–86, pl. 2, figs 1– 2; text-fig. Abb. branching sporophytes (see in Edwards and Kenrick, 2015) is beyond

146 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155

Fig. 2. A–D – Tichavekia grandis Pšenička, Sakala et Kraft, sp. nov.: A, D – Holotype, WBM F21761b; A – Overall view to large fragment of plant/sporophyte with proximal fertile part represented by sporangia, arrow – roundish thalloid structure, square – detail of sporangia figured on panel D; D – Detail with extremely short terminal dichotomy (arrow without label), each end bears one sporangium, XA – round distal structures on sporangium, XB – probably central vascular band; B – Isotype (counterpart of holotype), WBM F21761a; C – Camera lucida of both counterparts merged together, dichotomously axes show five levels (labeled A–F) of strictly isotomous branching, X? – point of probable dichotomy determined by approximation with the adjacent branch (dotted line). E–G – ?Fusiformitheca sp., WBM F21762: E – shows three levels of dichotomy with one preserved sporangium; F – Detail from panel E of long fusiform sporangium; G – Detail of last dichotomy (arrows) from panel E. All specimens from Kosov Quarry (northeastern part), all photographed in alcohol. the scope of the present paper. from the times of classical monographic works (e.g., Lang and Cookson, Occurrence. Kosov Quarry (northeastern part; south of the section 1935; Lang, 1937) with several overviews of Silurian and Early Devo- 356 by Kříž, 1992); Přídolí. nian floras having been published in the last two decades (Edwards and Wellman, 2001; Edwards and Richardson, 2004; Wellman et al., 2013). Upper Silurian terrestrial ecosystems were dominated by Cooksonia 3.1. Comments on other published taxa representing a sporophyte generation (Edwards and Kenrick, 2015). This iconic fossil plant was recently the subject of two interesting Current knowledge about Silurian floras has progressed significantly

147 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155 papers: one on the classification of the genus (Gonez and Gerrienne, Eocooksonia; see Xue et al., 2015). 2010a), and the other examining the role of Cooksonia in the early The determination of early land plant macrofossils represents a evolution of the embryophyte life cycle (Gerrienne and Gonez, 2011). special problem. In the past, all sterile axes with dichotomies were often At Kosov, three forms assigned or related to Cooksonia were described generally named as Cooksonia or Hostinella (Obrhel, 1962; Kotyk et al., by Obrhel (1962): Cooksonia cf. hemisphaerica, Cooksonia sp. and 2002; Libertín et al., 2003; Edwards et al., 2004). It is clear that in ?Cooksonia sp. many taxa of early land plants the telomes look the same, possess Cooksonia cf. hemisphaerica Lang 1937 as described by Obrhel identical modes of branching and are of a similar width (see Fig. 3A). (1962) corresponds to the original C. hemisphaerica description in Thus, these types of fossils cannot be relied on to distinguish taxa and having typically globose, hemispherical sporangia. We consider it as a only fertile remains are of a taxonomic value. Accordingly the number valid representative of this fossil genus, although M. Uhlířová (oral of specimens suitable for this study has been dramatically reduced from communication) correctly noticed there were up to five successive di- all available remains. chotomies, which is in contradiction with a new emended diagnosis of Cooksonia by Gonez and Gerrienne (2010a). 4. Plant associations Cooksonia sp. sensu Obrhel, 1962 is a fragmentary sporophyte with only one sporangium present. Obrhel (1962) put this specimen closer to The vascular plant association found in the Kosov Quarry comprises C. pertoni and we follow his statement, mainly based on typical shape of Tichavekia grandis Pšenička, Sakala et Kraft, gen. et sp. nov. (four spe- the sporangium. cimens; Fig. 2A–D, 4A), ?Fusiformitheca sp. (single specimen discovered; Obrhel's (1962) ?Cooksonia sp. represents a single specimen with Fig. 2E–G, 4F), Cooksonia cf. hemisphaerica Lang 1937 (one specimen unusually formed sporangia. Schweitzer (1980) considered it as another described by Obrhel, 1962; Fig. 4B), Cooksonia sp. sensu Obrhel, 1962 representative of his newly defined species C. bohemica (see below). (rare; two specimens known; Fig. 4D) and a number of sterile telomes/ However, we interpret this specimen as being attributable to our newly thalluses. They occur in fragments of various sizes. We suspect that the defined genus Tichavekia (see above). specimen of Aberlemnia bohemica (Schweitzer) Sakala, Pšenička et Kraft, As stated above, Schweitzer (1980) described from the area of Kosov comb. nov. (Fig. 4E) described by Schweitzer (1980) was probably Hill a new species of Cooksonia, C. bohemica (Fig. 4E). Our study of very found in a different but nearby place because no other specimen has detailed photos of the original material reveals an overall similar pat- been discovered during many visits to the site in the quarry studied by tern of sporangia including presence of a subdistal dehiscence line be- us. The Kosov locality represents the site with the highest diversity of tween the two valves of the individual sporangium, which is typical of four species in the northeastern part of the quarry but altogether five the recently defined fossil genus Aberlemnia (Gonez and Gerrienne, species are found in the area of the Kosov Hill. 2010b) and is clearly visible there. We consider that Schweitzer's The other place relatively rich in plants is near Karlštejn (Fig. 1). (1980) C. bohemica should be reassigned to the genus Aberlemnia and Baragwanathia brevifolia Kraft et Kvaček 2017 (Fig. 4C) and an un- therefore propose a new combination: Aberlemnia bohemica determined vascular plant were found there. The latter was mentioned (Schweitzer) Sakala, Pšenička et Kraft, comb. nov. (basionym: Cook- by Kraft and Kvaček (2017) based on oral information as belonging to sonia bohemica Schweitzer, Bonn. Palaeonbot. Mitt. 6, 1–34, 1980) in- Cooksonia. However, we found only a sterile telome from this locality in dicating its close relation to Lycophytina sensu Kenrick and Crane, 1997 the collections of the CGS. (Gonez and Gerrienne, 2010b). In summary, six early plant species occur in the Přídolí of the Prague Basin. All are proved or supposed to come from the N. parultimus-N. 3.2. Comments on other new material ultimus Zone (Fig. 5). Five species, reported from the Kosov area, were discovered near the Kosov Volcanic Centre, and two taxa, recorded in Associated with Tichavekia in the northeastern part of Kosov Quarry Karlštejn, were found near the Svatý Jan Volcanic Centre (Fig. 5). (south of the section 356 measured by Kříž, 1992), we found a small fragment of a leafless axis bearing three successive dichotomies 5. Discussion (Figs. 2E, G and 4F) with a 4 mm long fusiform sporangium on one distal part (Fig. 2F). It recalls Fusiformitheca (originally Fusitheca) fan- 5.1. Plant occurrences and environments ningiae (Wellman, Edwards et Axe) Xue et Wang, originally described by Wellman et al. (1998), later emended by Xue and Wang (2011) and also Stratigraphic and paleogeographic distribution of the early vascular recently illustrated by Edwards and Kenrick (2015, fig. 3m). Because no plants in the Prague Basin indicate a succession of environmental details were observed of the presumed in situ spores, which are im- changes in the areas that disappeared due to subsequent geological portant in the reliable generic determination of Fusiformitheca, we refer processes. Such areas existed for a limited time in the Silurian and to this specimen as ?Fusiformitheca sp. persisted probably to the Devonian. During the field research and taxonomic study of early vascular The plants had to grow in at least partly subaerial conditions of plants we encountered two difficulties. The first is related to conclusive terrestrial habitats. Although paleogeographic models of the region evidence of the plant nature of fossils, the second to the determination differ, the exposed land was most probably represented by several is- of plant taxa. It was difficult in some cases to decide if a fossil re- lands inside the Prague Basin. Such islands were likely of volcanic presents plant remains because it can be often very similar to a small origin as their existence coincides with the period of the maximum fragment of a dendroid graptolite. Both when preserved in organic volcanic activity during the late Silurian. They were represented by the compressions can look almost the same. The dendroids, especially the emerged parts of volcanic centres (Fig. 5); two are partly preserved genera Dendrograptus, Callograptus or Stelechocladia, which frequently inside the denudation relic of the Prague Basin, in the Svatý Jan (Měska occur in the Silurian of the Prague Basin, have sparsely arranged wide and Kratochvíl, 1946; Fiala, 1970; Kříž, 1992) and Kosov (Kříž, 1992) stipes without visible thecae which strongly resemble sterile axes of centres. However, their existence was apparently much longer. plants because there was no essential difference in the preserved or- Emerged lands in this part of peri-Gondwana commenced in the ganic material (Fig. 3). However, the mode of branching is quite dif- Prague Basin from the Wenlock (Kříž, 1992) and persisted to its closure ferent. Typical symmetrical dichotomies of plants can be distinguished in the Givetian. The remains of land plants occur in the marine sedi- from the prevailing pseudomonopodial branching of dendroids when ments of the basin with varying frequency and taxonomic composition preserved without any secondary deformation. On the other hand, this during almost its entire post-Llandoverian history (Obrhel, 1968, feature is not entirely unequivocal because of the exceptional existence 1991). The character of the areas, where the plants grew, also changed. of pseudomonopodial branching in some late Silurian plants (e.g. At the beginning of the colonization history in the Silurian, there is firm

148 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155

Fig. 3. Fragment of dendroid graptolite Dendrograptus sp. (B), typical example il- lustrating the mode of preservation con- fusing with plant remains (A). A – Kosov Quarry (northeastern part), Požáry Formation, Přídolí; B – Kosov Quarry (southeastern part), Kopanina Formation, Ludlow. Both samples of identical magnifi- cation; scale bar equals 5 mm.

evidence for plant habitats to be situated on volcanic islands. An ap- of the Kopanina Formation distributed around the volcanic centres and proaching front of the Variscan Orogen during the Middle Devonian also well-documented from other places in the Prague Basin. In con- (Givetian) caused uplift which had a decisive influence on the trast, the relatively short epoch of the Přídolí yielded plenty of fossil spreading of the plant habitats in the region of the Prague Basin at the plant remains. This indicates that the relief of the coastal area of end of its history, when the local diversity and abundance also reached emerged islands during the Wenlock offered suitable areas where plants their maxima (Obrhel, 1968). Between these two points in the tectonic could prosper. The islands can be visualized as of a low altitude with a history of the basin, the Lochkovian to Eifelian succession is dominated flat seashore which, through constant erosion, provided places with by marine carbonate rocks. However, land plants are occasionally suitable substrate for attachment of plants. Increasing volcanic activity found in these marine sediments (Obrhel, 1968, 1991) along with some during the Ludlow changed the relief of the islands which is interpreted fish fossils that are interpreted to dwell in brackish water (Vaškaninová to have become higher with a steep rocky shore. High energy of the surf and Kraft, 2016 based on data of Havlíček, 1998), implying that and an absence of soft substrate is an obstacle for the plant colonization emergent dry land (possibly initially the eroding remnants of volcanic even of modern island coasts with their comparatively advanced plants, islands) coexisted with deposition in the prevailing marine basin. To which are, in addition, not only sea-dispersed (e.g. Ball and Glucksman, explain the intermittent occurrence of emergent land in the subsequent 1975; Thornton et al., 2001). It was shown by Horný (1955) and Kříž Lower Devonian history of the Prague Basin, tectonism and/or sea level (1992) that volcanic activity had gradually decreased and ceased fluctuations are the most probable causes. during the middle Ludlow. The absence of vascular plants in the Ko- The vascular plants provide the best paleobiological evidence of the panina Formation could be emphasized by the generally lower plant proximity of terrestrial environments. Rare supporting evidence was diversity during this time (see above). Once volcanism terminated, an given also in the Devonian by the occurrence of an agnathan vertebrate erosion and corrosion of the islands slowly re-modelled their reliefs, the (Schizosteus perneri) belonging to the group generally considered to live land became gradually lower with coastal profiles that sloped much in fresh or brackish water (Vaškaninová and Kraft, 2016). more gently to the sea. Erosion produced and accumulated a suitable The earliest history of the islands with primitive vegetation during substrate along the coast line again and the second plant community the Silurian has two phases: firstly in the Wenlock (insufficiently stu- was able to colonize it. This community was more diversified as the died; based on material described by Libertín et al., 2003, 2018 and evolution of the plants had produced a number of new forms during the unpublished material deposited in CGS; cryptospores discussed by Kříž, late Silurian. Whereas the first community during the Wenlock was very 1992) and subsequently with a broad peak in the Přídolí (this study). probably monospecific, the second of Přídolí age was composed of We interpret the distribution pattern of the vascular plants especially in several (at least six) species (Fig. 4). terms of changes in the relief and character of the islands. Thus, we The above model of the permanent existence of islands in the region consider the distribution as a succession of the subsequent pioneer plant of the Prague Basin during the Silurian and extending into the Devonian communities rather than early invasion accompanied by suppression fits the results of Kříž (1992) who described details of their history with and replacement of species. respect to volcanism, tectonic movements of individual blocks of the The earliest evidence of vascular plants in the Prague Basin occurs basin, fluctuations of the sea level and facies pattern resulted from se- in the late Sheinwoodian (Wenlock) tuffaceous shale of the Motol dimentation in the shallow-water environment around them. Formation belonging to Cyrtograptus rigidus/Monograptus belophorus The limited distribution of plant remains in the number of localities Zone (Libertín et al., 2003). No land plants have been so far recorded in of the Požáry Formation (Přídolí) also indicates that there was not a the Kopanina Formation (Ludlow) as far as we are aware having in- uniform vegetated zone including all plants, but rather that the area spected numerous fossil collections. We suppose the plants to be absent was environmentally fragmented and the individual taxa occurred on or extremely rare at this level despite a rich fossil record from outcrops the coast separately or in particular associations. It can be interpreted

149 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155

Fig. 4. Gallery of plants recorded in the Přídolí (N. parultimus-N. ultimus Zone) in the Prague Basin. A – Tichavekia grandis Pšenička, Sakala et P. Kraft, sp. nov., WBM F21761a; B – Cooksonia cf. hemisphaerica Lang 1937, NM D-475; C – Baragwanathia brevifolia Kraft et Kvaček 2017, CGS KR 1; D – Cooksonia sp. sensu Obrhel, 1962, private coll. of M. Uhlířová; E – Aberlemnia bohemica (Schweitzer) Sakala, Pšenička et Kraft, comb. nov., SMNH JE-Sch0260B; F – ?Fusiformitheca sp., WBM F21762. A, B, D, F, – Kosov Quarry; C – Karlštejn; E – Dlouhá Hora. All scales equal 10 mm. as reflecting a distribution of habitats along the coast. These primordial Those vegetated coastal segments had to be not only of suitable “patches” are observable from Beroun to the Karlštejn area (Fig. 5). The substrate and effectively protected against devastating wind and waves coastal segment represented by “Dlouhá hora” (southern part of the but also had to be humid enough, with fresh-water supply and reach- Kosov area) was typically populated by Aberlemnia bohemica (data from able by water-dispersion. The humid habitats were located in wet cli- Schweitzer, 1980; originally described as Cooksonia bohemica); Kosov mate zone or, at least, in local microclimates. The local environment Quarry (northern part of the Kosov area) coastal segment provided a had to be stable for sufficient time to accommodate land plants per- habitat for Cooksonia, Tichavekia and Fusiformitheca (this study); and manently or periodically. A stable supplementation of fresh water could the Karštejn segment hosted ?Cooksonia and Baragwanathia (Kraft and be secured by permanent streams or seeps rather than rains or con- Kvaček, 2017). The former two sites were situated in the southwestern densed air humidity with respect to the early plant morphology. Spores part, the latter in the southeastern of the volcanic island. The minimal or plant fragments which enabled subsequent reproduction and spread fragmentation of several plant remains suggests a very short transport out had to be transported to the coastal segments in the sea-water en- and relatively low water dynamics before their burial in the marine vironment (Kraft and Kvaček, 2017) as wind-borne and zoochorous sediment. Therefore, the mentioned localities most probably were si- ways can be respectively considered to have a very limited effect or to tuated close to the vegetated coastal segments and were influenced only be excluded for that time. Even if all mentioned circumstances are clear by local currents and partly also by wind. A location on the leeward side preconditions of the plant terrestrialization, it is quite difficult to of the island is more probable because of lower dynamic of the surf zone imagine these primitive floras being widely distributed along sea coasts. influencing the coast. In this sense, the Initial Plant Diversification and Dispersal Event

150 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155

Fig. 5. Reconstruction of the Silurian volcanic islands in the southwestern part of the central Prague Basin, their supposed changes in time and reconstructed places of the plant distribution based on fossil records from the surrounding marine sediments. (Based on Horný, 1955, tab. 7II–VIII and Kříž, 1992; modified). The localities are identical as in Fig. 1; their stratigraphic positions are shown in the stratigraphic column. Note that this column is not made in any proportion and the maximum extensions of the volcanic centres (map below) are sketched schematically after Kříž (1992). The data on plant occurrences used for the localities: 1 – Kosov Quarry and Dlouhá hora from own collections, Obrhel (1962) and Schweitzer (1980);2– Karlštejn from Kraft and Kvaček (2017);3– Loděnice from Libertín et al. (2003);4– Koněprusy from material reposited in CGS, collected from the section 781, layer no. 13, described by Kříž et al. (1993, p. 813).

151 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155

(IPDDE) of the Přídolí (as well as previous and, maybe, subsequent Ludfordian CIE (5) is the only one of all Silurian CIEs documented in the stages) was apparently patchy in time and space. Dynamic coasts af- Prague Basin with a distinct climatic cooling at the onset of the isotope fected by tectonic processes and volcanism enabled formation and re- anomaly proved directly by the δ18O composition of bioapatite (Lehnert juvenation of suitable environments and habitats. Islands, especially et al., 2007b). Extinction predated the Silurian/Devonian boundary those of volcanic origin, played a key role in acting as transfer points for (Klonk) CIE (6) and the associated transgrediens graptolite Event was long-distance dispersion (Kraft and Kvaček, 2017; cf. Cain et al., 2000 related to an anoxic or disoxic event in the period affecting many for modern equivalents) with a high capability to accommodate new bottom-dwelling species (Hladíková et al., 1997; Manda and Frýda, arrivals (cf. van Kleunen et al., 2015 for modern islands). These aspects 2010). can be also considered to cause quite distinct taxonomic divergence of As mentioned above, all prominent positive carbon isotope vegetated areas (Edwards and Wellman, 2001; Wellman et al., 2013)as anomalies are always predated by a rapid, globally documented fall in documented even from modern island ecosystems: disharmonic floras sea level. This fact was commonly interpreted as evidence for rapid by Carlquist (1974) discussed fittingly by Denslow (2003) and high cooling and change in the climatic regime (Jeppsson, 1990; Munnecke degrees of endemism reported by Kier et al. (2009). et al., 2003; Calner, 2008; Calner and Eriksson, 2006). However, the latter climatic changes were inferred only indirectly from the sedi- 5.2. Discussion of global aspects: carbon anomalies, marine extinction mentological data. Nevertheless, Trotter et al. (2016) recently pub- events and climatic changes lished the first record of the Silurian climate determined from conodont 18 18 δ O compositions (δ Ophos). The seawater temperature record, as well The Silurian Period was a time of several distinct and rapid changes as climatic conditions, well fits previously discussed climatic conditions in the global carbon cycle. These geochemical events, measured inferred from depositional data. through δ13C excursions, were closely related to major crises in marine Occurrences of all above-mentioned carbon isotope anomalies in the ecosystems as well as to paleoclimatic changes (see Jeppsson, 1998; Prague Basin associated with rapid regressions makes it possible to Munnecke et al., 2003, 2010; Noble et al., 2005, 2012; Loydell, 2007; analyse a link between climatic conditions and Barrandian vascular Calner, 2008; Cramer et al., 2011; Trotter et al., 2016 for reviews). The plant associations. The oldest vascular plants, coming from the global carbon cycle with complex biogeochemical pathways has im- Wenlockian C. rigidus/M. belophorus Biozone (Libertín et al., 2003), pacted not only on the Earth's climate but also on the evolution of appeared during a warmer interval after the second largest CIE, the marine and terrestrial ecosystems over geological time. The Silurian early Sheinwoodian (Ireviken) CIE (3), which represented a cool period Period (lasting only about 25 Myr) represents a rather unstable period (Trotter et al., 2016). Similarly, the vascular plant association com- in the Earth's history because it is characterized by six major positive posed of at least six species from the Přídolian N. parultimus-N. ultimus carbon isotope excursions (CIE); numbered from oldest to youngest: (1) Biozone, discussed herein, occurs during a warm period after a cool the early Aeronian CIE, (2) the late Aeronian CIE, (3) the early Shein- interval associated with the mid-Ludfordian (Lau) CIE (5) (Lehnert woodian (Ireviken) CIE, (4) the Homerian (Mulde) CIE, (5) the mid- et al., 2007b; Frýda, unpub. data). It is noteworthy, that both vascular Ludfordian (Lau) CIE and (6) the pre-Silurian/Devonian boundary plant associations occurred when a large part of the regional carbonate (Klonk) CIE. Most of the CIEs were documented on different paleo- platform was exposed and partly erroded which was especially the case continents including tropical as well as mid latitudal regions (Cramer for the mid-Ludfordian (Lau) CIE (5) in the Prague Basin. Subaerial et al., 2011). Munnecke et al. (2003, 2010) compiled common features exposure of the carbonate platform can be considered to result in a of the Silurian CIEs from various paleocontinents and showed that the suitable substrate (“soil”) production spreading habitats suitable for the positive carbon isotope anomalies are predated by extinction events in primitive vascular plants (Fig. 6). marine ecosystems. The latter extinctions are each associated with a rapid regression which seems to be climatically driven (Calner, 2008; 6. Conclusions Lehnert et al., 2010; Cramer et al., 2011; Trotter et al., 2016). Most of the positive δ13C anomalies were first described from pa- Based on several independent models, the Prague Basin and its is- leotropical regions, especially from Baltica (see Calner, 2008 for re- lands were situated in the Rheic Ocean at the periphery of the wide view), and their global distribution was recognized later. During the Gondwanan shelf, i.e. far from the Gondwanan craton in the outer last several years most of the Silurian major positive δ13C anomalies periphery of a marginal sea. Plant colonization in the region implies a were documented also in the Prague Basin which was located about 30° significant role for islands in plant dispersion. The spores transported S of the paleoequator (e.g., Franke et al., 2017), i.e. at mid-paleolati- by ocean currents used such islands, especially in warmer climatic tudinal zone. zones, as an intermediate habitat on the way to global distribution. The late Aeronian CIE (2), the associated graptolite sedgwickii ex- Humid microclimate, a variety of environments and substrates, and tiction event and a rapid marine regression was hitherto documented isolation of the island coasts were ideal prerequisites for development only in graptolitic shale facies (Štorch and Frýda, 2012). The early of plant diversity. Although significant differences exist between early Sheinwoodian (Ireviken) CIE (3) was also linked with rapid regression. land plant vegetation and modern angiosperm-prevailing flora, making However, it belongs to less-known CIEs in the Silurian of the Prague an actualistic approach very weak in many aspects, there are many Basin (Frýda et al., 2015). The double-peaked Homerian (Mulde) CIE similarities to modern coastal habitats, especially those on islands. (4), predated by the lundgreni extinction Event and a rapid regression, Today such islands are gateways for many pioneer as well as invasion was documented both from the graptolitic shale and limestone facies taxa and islands situated in the tropical climate zones are widely re- (Kozłowska-Dawidziuk et al., 2001; Frýda and Frýdová, 2014, 2016). garded as centres of plant diversity. The role of islands in the early One of the largest positive carbon isotope excursions of the entire dispersion of plants is by comparison largely unrecognized and the is- Phanerozoic, the mid-Ludfordian (Lau) CIE (5), as well as the oldest lands in the Prague Basin were apparently among those playing a key known Silurian/Devonian boundary (Klonk) CIE (6), is both well-doc- role in this process, strongly influenced by local environment dynamics ummented in the Prague Basin. The mid-Ludfordian CIE (5) was pre- as well as global climatic and sea level changes. dated by the conodont Lau and graptolite kozlowskii bioevents (Štorch, The described plant association is a last piece of the puzzle illus- 1995; Slavík et al., 2010). This positive δ13C anomaly (Frýda and trating a special position of the Bohemian Massif in plant evolution. The Manda, 2013) is associated with a large regression within the Prague Early Paleozoic history from its beginning in the early Silurian is re- Basin producing a stratigraphic gap in shallow water depositional en- corded in its part, the Central Bohemian Unit with the relic of the vironments (Lehnert et al., 2007a; Gocke et al., 2013) and erosional Prague Basin. The global Initial Plant Diversification and Dispersal surfaces in deeper water environments (Manda et al., 2012). The mid- Event (IPDDE) in the Přídolí, epoch of the late Silurian (studied herein),

152 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155

Fig. 6. Visualization of the early land plant habitat in the landward margin of the abrasion platform of inactive vol- canic island during a regressive event in Přídolí, late Silurian. Such environ- ment is supposed in the emerged top of the Kosov Volcanic Centre. The tide range on the seaward side of the plat- form (tidal flat) and reach of the storm waves are illustrated by extent of ce- phalopod and trilobite shells. The plants growing above this limit are considered to be torn off during ex- ceptional storms. Their remains asso- ciated with shells in the foreground (highlighted darker) could be trans- ported also individually when they died or because of wind or rain. (The cephalopod shells in the foreground are 15–20 cm long.)

attaining a local diversity and distribution maximum in the Givetian (660 pp.). (Middle Devonian) are major paleobotanical features of this region in Chlupáč, I., 1999. Barrande's stratigraphic concepts, palaeontological localities and tra- – – – fl dition comparison with the present state. J. Czech Geol. Soc. 44 (1 2), 3 30. the Early Paleozoic. Rich Late Paleozoic oras of the Euro-American Clarke, J.T., Warnock, R., Donoghue, P.C., 2011. Establishing a time-scale for plant tropical realm are related to the humid periods in Carboniferous and evolution. New Phytol. 192 (1), 266–301. https://doi.org/10.1111/j.1469-8137. partly also to the Permian of the Bohemian Massif. They illustrate an 2011.03794.x. Cocks, L.R.M., Torsvik, T.H., 2002. Earth geography from 500 to 400 million years ago: a early gymnosperm expansion. Cretaceous plants preserved in con- faunal and palaeomagnetic review. J. Geol. Soc. Lond. 159 (6), 631–644. https://doi. tinental as well as marine sediments document an early history of an- org/10.1144/0016-764901-118. giosperms. Cenozoic plant history in the Bohemian Massif is a quite Cramer, B.D., Brett, C.E., Melchin, M.J., Männik, P., Kleffner, M.A., McLaughlin, P.I., complete record of climate-related changes. Thus, the key events of Lloydell, D.K., Munnecke, A., Jeppsson, L., Corradini, C., Brunton, F.R., Saltzman, M.R., 2011. Revised correlation of Silurian provincial series of North America with 13 plant evolution are now completed in the unique Central European area global and regional chronostratigraphic and δ Ccarb chemostratigraphy. Lethaia 44 providing a very rich fossil record through the whole history of plant (2), 185–202. https://doi.org/10.1111/j.1052–3931.2010.00234.x. evolution. Denslow, J.S., 2003. Weeds in paradise: thoughts on the invasibility of tropical islands. Ann. Mo. Bot. Gard. 90 (1), 119–127. https://doi.org/10.2307/3298531. Edwards, D., Kenrick, P., 2015. The early evolution of land plants, from fossils to geno- Acknowledgments mics: a commentary on Lang (1937) ‘On the plant-remains from the Downtonian of England and Wales’. Philos. Trans. R. Soc. Lond. B 370 (1666), 20140343. https:// š doi.org/10.1098/rstb.2014.0343. We are obliged to Franti ek Tichávek for kindly making his collec- Edwards, D., Richardson, J.B., 2004. Silurian and Lower Devonian plant assemblages tion of Silurian plants available for study. We thank Monika Uhlířová from the Anglo-Welsch Basin: a palaeobotanical and palynological synthesis. Geol. J. and Jan Thuma for loans of specimens from their private collections 39 (3–4), 375–402. https://doi.org/10.1002/gj.997. č fi Edwards, D., Wellman, C.H., 2001. Embryophytes on land: the Ordovician to Lochkovian and Martin Sou ek for his help in the eld. We are grateful to Thomas (Lower Devonian) record. In: Gensel, P.G., Edwards, D. (Eds.), Plants Invade the Denk (SMNH Stockholm) and Jiří Kvaček (NM Praha) for photos of Land. Evolutionary and Environmental Perspectives. Columbia University Press, New specimens housed in collections of their institutions, and Jiří Svoboda York, pp. 3–28. Edwards, D., Feehan, J., Smith, D.G., 1983. A late Wenlock flora from Co. Tipperary, for drawing of landscape reconstruction. We thank two anonymous Ireland. Bot. J. Linn. Soc. 86 (1–2), 19–36. https://doi.org/10.1111/j.1095-8339. reviewers for their very constructive comments improving our manu- 1983.tb00715.x. script. We are obliged to Ian Percival (Geological Survey of New South Edwards, D., Wellman, C.H., Axe, L., 1999. Tetrads in sporangia and spore masses from Wales) for his language improvement and his valuable comments. This the Upper Silurian and Lower Devonian of the Welsh Borderland. Bot. J. Linn. Soc. 130 (2), 111–156. https://doi.org/10.1111/j.1095-8339.1999.tb00515.x. paper was supported by the project Progress Q45 of the Charles Edwards, D., Banks, H.P., Ciurca Jr., S.J., Laub, R.S., 2004. NewSilurian cooksonias from University, Prague (to P.K. and J.S.) and projects of Grant Agency of dolostones of north-eastern North America. Bot. J. Linn. Soc. 146 (4), 399–413. Czech Republic GAP210/12/2053 (to J.P.) and GA17-18120S (to J.F.). https://doi.org/10.1111/j.1095-8339.2004.00332.x. fi Fiala, F., 1970. Silurian and Devonian diabases of the Barrandian Basin, Sborník Part of the studied material was collected with nancial support of the geologických věd, Řada G. 17, 7–89 (in Czech, English summary). West Bohemian Museum in Plzeň through the project no. UUP 2015/1 Franke, W., Cocks, L.R., Torsvik, T.H., 2017. The Palaeozoic Variscan oceans revisited. (to P.K.). Gondwana Res. 48, 257–284. https://doi.org/10.1016/j.gr.2017.03.005. Frýda, J., Frýdová, B., 2014. First evidence for the Homerian (late Wenlock, Silurian) positive carbon isotope excursion from peri-Gondwana: new data from the References Barrandian (Perunica). Bull. Geosci. 89 (3), 617–634. https://doi.org/10.3140/bull. geosci.1493. Frýda, J., Frýdová, B., 2016. The Homerian (late Wenlock, Silurian) carbon isotope ex- Ball, E., Glucksman, J., 1975. Biological colonization of Motmot, a recently-created tro- cursion from Perunica: does dolomite control the magnitude of the carbon isotope – pical island. Proc. R. Soc. Lond. B 190 (1101), 421 442. https://doi.org/10.1098/ excursion? Can. J. Earth Sci. 53 (7), 695–701. https://doi.org/10.1139/cjes-2015- rspb.1975.0104. 0188. Cain, M.L., Milligan, B.G., Strand, A.E., 2000. Long distance seed dispersal in plant po- Frýda, J., Manda, Š., 2013. A long–lasting steady period of isotopically heavy carbon in – pulations. Am. J. Bot. 87 (9), 1217 1227. https://doi.org/10.2307/2656714. the late Silurian ocean: evolution of the δ13C record and its significance for an in- – Calner, M., 2008. Silurian global events at the tipping point of climate change. In: tegrated δ13C, graptolite and conodont stratigraphy. Bull. Geosci. 88 (2), 463–482. – Ashraf, M.T. (Ed.), Mass Extinctions. Springer-Verlag, Berlin, Heidelberg, pp. 21 58. https://doi.org/10.3140/bull.geosci.1436. – – – – https://doi.org/10.1007/978 3 540 75916 4_4. Frýda, J., Lehnert, O., Joachimski, M., 2015. First record of the early Sheinwoodian Calner, M., Eriksson, M.J., 2006. Evidence for rapid environmental changes in low lati- carbon isotope excursion (ESCIE) from the Barrandian area of northwestern tudes during the Late Silurian Lau Event: the Burgen-1 drillcore, Gotland, Sweden. peri–Gondwana. Estonian J. Earth Sci. 64 (1), 42–46. https://doi.org/10.3176/earth. – Geol. Mag. 143 (1), 15 24. https://doi.org/10.1017/S001675680500169X. 2015.8. Carlquist, S., 1974. Island Biology. Columbia University Press, New York, London Gerrienne, P., Gonez, P., 2011. Early evolution of life cycles in embryophytes: a focus on

153 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155

the fossil evidence of gametophyte/sporophyte size and morphological complexity. J. Soc. Lond. B 224 (517), 421–449. https://doi.org/10.1098/rstb.1935.0004. Syst. Evol. 49 (1), 1–16. https://doi.org/10.1111/j.1759-6831.2010.00096.x. Lehnert, O., Frýda, J., Buggisch, W., Munnecke, A., Nützel, A., Kříž, J., Manda, Š., 2007a. Gerrienne, P., Servais, T., Vecoli, M., 2016. Plant evolution and terrestrialization during δ13C record across the Ludlow Lau Event: new data from mid palaeo–latitudes of Palaeozoic times – the phylogenetic context. Rev. Palaeobot. Palynol. 227, 4–18. northern peri–Gondwana (Prague Basin, Czech Republic). Palaeogeogr. https://doi.org/10.1016/j.revpalbo.2016.01.004. Palaeoclimatol. Palaeoecol. 245 (1–2), 227–244. https://doi.org/10.1016/j.palaeo. Gocke, M., Lehnert, O., Frýda, J., 2013. Facies development and palynomorphs during the 2006.02.022. Lau Event (Late Silurian) in a non-tropical carbonate environment: shallow and deep Lehnert, O., Eriksson, M.J., Calner, M., Joachimski, M., Buggisch, W., 2007b. Concurrent water examples from the Barrandian Area (Czech Republic). Facies 59 (3), 611–630. sedimentary and isotopic indications for global climatic cooling in the Late Silurian. https://doi.org/10.1007/s10347-012-0328-y. Acta Palaeontol. Sin. 46, 249–255 (Suppl.). Gonez, P., Gerrienne, P., 2010a. A new definition and a lectotypification of the genus Lehnert, O., Mannik, P., Joachimski, M.M., Calner, M., Frýda, J., 2010. Palaeoclimate Cooksonia Lang 1937. Int. J. Plant Sci. 171 (2), 199–215. https://doi.org/10.1086/ perturbations before the Sheinwoodian glaciation: a trigger for extinctions during the 648988. ‘Ireviken Event’. Palaeogeogr. Palaeoclimatol. Palaeoecol. 296 (3–4), 320–331. Gonez, P., Gerrienne, P., 2010b. Aberlemnia caledonica gen. et comb. nov., a new name for https://doi.org/10.1016/j.palaeo.2010.01.009. Cooksonia caledonica Edwards 1970. Rev. Palaeobot. Palynol. 163, 64–72. https:// Libertín, M., Labuťa, R., Dašková, J., 2003. The oldest vascular plants from the Bohemian doi.org/10.1016/j.revpalbo.2010.09.005. Massif, Zprávy o geologických výzkumech v roce 2002. 127 (In Czech, English Havlíček, V., 1981. Development of a linear sedimentary depression exemplified by the summary.). Prague basin (Ordovician–Middle Devonian; Barrandian area – central Bohemia). Libertín, M., Kvaček, J., Bek, J., Žárský, V., Štorch, P., 2018. Sporophytes of poly- Sbor. geol. Věd, Geol. 35, 7–48. sporangiate land plants from the early Silurian period may have been photo- Havlíček, V., 1998. Variscan folding and faulting in the Lower Palaeozoic basins. In: synthetically autonomous. Nat. Plants 4, 269–271. https://doi.org/10.1038/s41477- Chlupáč, I., Havlíček, V., Kříž, J., Kukal, Z., Štorch, P. (Eds.), Palaeozoic of the 018-0140-y. Barrandian (Cambrian to Devonian). Czech Geological Survey, Prague, pp. 165–169. Loydell, D.K., 2007. Early Silurian positive δ13C excursions and their relationship to Havlíček, V., Vaněk, J., Fatka, O., 1994. Perunica microcontinent in the Ordovician (its glaciations, sea–level changes and extinction events. Geol. J. 42 (5), 531–546. position within the Mediterranean Province, series division, benthic and pelagic as- https://doi.org/10.1002/gj.1090. sociations). In: Sbor. geol. Věd, Geol. 46. pp. 23–56. Loydell, D.K., 2012. Graptolite biozone correlation charts. Geol. Mag. 149 (1), 124–132. Hladíková, J., Hladil, J., Kříbek, B., 1997. Carbon and oxygen isotope record across https://doi.org/10.1017/S0016756811000513. Pridoli to Givetian stage boundaries in the Barrandian basin (Czech Republic). Manda, Š., Frýda, J., 2010. Silurian–Devonian boundary events and their influence on Palaeogeogr. Palaeoclimatol. Palaeoecol. 132 (1), 225–241. https://doi.org/10. cephalopod evolution: evolutionary significance of cephalopod egg size during mass 1016/S0031-0182(97)00062-X. extinctions. Bull. Geosci. 85 (3), 513–540. https://doi.org/10.3140/bull.geosci.1174. Horný, R., 1955. The Budňany Beds in the Western Part of the Silurian of the Barrandian. Manda, Š., Štorch, P., Slavík, L., Frýda, J., Kříž, J., Tasáryová, Z., 2012. Graptolite, Sborník Ústředního ústavu geologického, oddíl geologický 21 (2), 315–447. conodont and sedimentary record through the late Ludlow Kozlowskii Event Jeppsson, L., 1990. An oceanic model for lithological and faunal changes tested on the (Silurian) in shale dominated succession of Bohemia. Geol. Mag. 149 (3), 507–531. Silurian record. J. Geol. Soc. Lond. 147 (4), 663–674. https://doi.org/10.1144/gsjgs. https://doi.org/10.1017/S0016756811000847. 147.4.0663. Měska, G., Kratochvíl, J., 1946. Geological and Petrological Notes Concerning a Rock Jeppsson, L., 1998. Silurian oceanic events: Summary of general characteristics. In: From the Neighbourhood of Sv. Jan pod Skalou, Classified as Basalt. Sbor. St. geol. Landing, E., Johnson, M.E. (Eds.), Silurian Cycles: Linkages of Dynamic Stratigraphy Úst. Čs. Republ. 13. pp. 189–205 (in Czech, Russian and English summaries). With Atmospheric, Oceanic and Tectonic Changes. New York State Museum Bulletin Munnecke, A., Samtleben, C., Bickert, T., 2003. The Ireviken Event in the lower Silurian 491. pp. 239–257. of Gotland, Sweden – relation to similar Palaeozoic and Proterozoic events. Kenrick, P., Crane, P.R., 1991. Water-conducting cells in early fossil land plants: im- Palaeogeogr. Palaeoclimatol. Palaeoecol. 195 (1–2), 99–124. https://doi.org/10. plications for the early evolution of tracheophytes. Bot. Gaz. 152 (3), 335–356. 1016/S0031-0182(03)00304-3. https://doi.org/10.1086/337897. Munnecke, A., Calner, M., Harper, D.A.T., Servais, T., 2010. Ordovician and Silurian Kenrick, P., Crane, P.R., 1997. The Origin and Early Diversification of Land Plants. A sea–water chemistry, sea level, and climate: a synopsis. Palaeogeogr. Palaeoclimatol. Cladistic Study. Smithsonian Institute Press, Washington DC and London (441 pp.). Palaeoecol. 296 (3–4), 389–413. https://doi.org/10.1016/j.palaeo.2010.08.001. Kenrick, P., Wellman, C.H., Schneider, H., Edgecombe, G.D., 2012. A timeline for ter- Noble, P.J., Zimmerman, M.K., Holmden, C., Lenz, A.C., 2005. Early Silurian restrialization: consequences for the carbon cycle in the Palaeozoic. Philos. Trans. R. (Wenlockian) δ13C profiles from the Cape Phillips Formation, Arctic Canada and their Soc. Lond. B 367 (1588), 519–536. https://doi.org/10.1098/rstb.2011.0271. relation to biotic events. Can. J. Earth Sci. 42 (8), 1419–1430. https://doi.org/10. Kier, G., Kreft, H., Lee, T.M., Jetz, W., Ibisch, P.L., Nowicki, C., Mutke, J., Barthlott, W., 1139/e05-055. 2009. A global assessment of endemism and species richness across island and Noble, P.J., Lenz, A.C., Holmden, C., Masiak, M., Zimmerman, M.K., Poulson, S.R., mainland regions. PNAS 106 (23), 9322–9327. https://doi.org/10.1073/pnas. Kozłowska, A., 2012. Isotope geochemistry and plankton response to the Ireviken 0810306106. (Earliest Wenlock) and Cyrtograptus lundgreni Extinction Events, Cape Phillips van Kleunen, M., Dawson, W., Essl, F., Pergl, J., Winter, M., Weber, E., Kreft, H., Weigelt, Formation, Arctic Canada. In: Talent, J.A. (Ed.), Earth and Life – Global Biodiversity, P., Kartesz, J., Nishino, M., Antonova, L.A., Barcelona, J.F., Cabezas, F.J., Cárdenas, Extinction Intervals and Biogeographic Perturbations Through Time. Series: D., Cárdenas-Toro, J., Castaño, N., Chacón, E., Chatelain, C., Ebel, A.L., Figueiredo, International Year of Planet Earth Springer, Dordrecht, Heidelberg, London, New E., Fuentes, N., Groom, Q.J., Henderson, L., Inderjit, Kupriyanov, A., Masciadri, S., York, pp. 631–652. https://doi.org/10.1007/978–90–481–3428–1_12. Meerman, J., Morozova, O., Moser, D., Nickrent, D.L., Patzelt, A., Pelser, P.B., Obrhel, J., 1962. Die Flora der Přídolí-Schichten (Budňany-Stufe) des mittelböhmischen Baptiste, M.P., Poopath, M., Schulze, M., Seebens, H., Shu, W.-S., Thomas, J., Silurs. Geologie 11, 83–97. Velayos, M., Wieringa, J.J., Pyšek, P., 2015. Global exchange and accumulation of Obrhel, J., 1968. Der Silur- und Devonflora des Barrandiums. Paläont. Abh., Abt. B 2, non-native plants. Nature 525 (7567), 100–103. https://doi.org/10.1038/ 661–706. nature14910. Obrhel, J., 1991. Rostlinné fosílie z nemetamorfovaného staršího paleozoika Čech a Kotyk, M.E., Basinger, J.F., Gensel, P.G., de Freitas, T.A., 2002. Morphologically complex Moravy. Čas. Mineral. Geol. 36 (4), 263–277. plant macrofossils from the Late Silurian of Arctic Canada. Am. J. Bot. 89 (6), von Raumer, J.F., Stampfli, G.M., Arenas, R., Sánchez Matínez, S., 2015. Ediacaran to 1004–1013. https://doi.org/10.3732/ajb.89.6.1004. Cambrian oceanic rocks of the Gondwana margin and their tectonic interpretation. Kozłowska-Dawidziuk, A., Lenz, A., Štorch, P., 2001. Upper Wenlock and Lower Ludlow Int. J. Earth Sci. 104 (5), 1107–1121. https://doi.org/10.1007/s00531-015-1142-x. (Silurian), post–extinction graptolites, Všeradice section, Barrandian Area, Czech (Geologische Rundschau). Republic. J. Paleontol. 75 (1), 147–164. https://doi.org/10.1017/ Salamon, M., Gerrienne, P., Steemans, P., Gorzelak, P., Filipiak, P., Le Hérissé, A., Paris, S0022336000031966. F., Cascales-Miñana, B., Brachaniec, T., Misz-Kennan, M., Niedźwiedzki, R., Trela, W., Kraft, P., Kvaček, Z., 2017. Where the lycophytes come from? – a piece of the story from 2018. Putative Late Ordovician land plants. New Phytol. 218, 1305–1309. https:// the Silurian of peri-Gondwana. Gondwana Res. 45, 180–190. https://doi.org/10. doi.org/10.1111/nph.15091. 1016/j.gr.2017.02.001. Schweitzer, H.-J., 1980. Die Gattungen Renalia Gensel und Psilophyton Dawson im Kříž, J., 1991. The Silurian of the Prague Basin (Bohemia) – tectonic, eustatic and vol- Unterdevon des Rheinlandes. In: Bonner paläobot. Mitt. 6. pp. 1–34. canic controls of facies and faunal development. In: Bassett, M.G., Lane, P.D., Scotese, C.R., 2001. Atlas of Earth History. vol. 1 PALEOMAP Project, Arlington, Texas Edwards, D. (Eds.), The Murchison Symposium: Proceedings of an International (58 pp.). Conference on the Silurian System. Special Papers in Palaeontology 44. pp. 179–203. Servais, T., Sintubin, M., 2009. Avalonia, Armorica, Perunica: terranes, microcontinents, Kříž, J., 1992. Silurian Field Excursions. Prague Basin (Barrandian), Bohemia. Geological microplates or palaeobiogeographical provinces? In: Bassett, M.G. (Ed.), Early Series No. 13 National Museum of Wales, Cardiff (111 pp.). Palaeozoic Peri-Gondwana Terranes: New Insights from Tectonics and Biogeography. Kříž, J., 1998. Silurian. In: Chlupáč, I., Havlíček, V., Kříž, J., Kukal, Z., Štorch, P. (Eds.), Geological Society of London, Special Publication 325. pp. 103–115. https://doi.org/ Palaeozoic of the Barrandian (Cambrian to Devonian). Czech Geological Survey, 10.1144/SP325.5. Prague, pp. 79–101. Slavík, L., Kříž, J., Carls, P., 2010. Reflection of the mid-Ludfordian Lau Event in con- Kříž, J., Jaeger, H., Paris, F., Schönlaub, H.P., 1986. Přídolí – the fourth subdivison of the odont faunas of Bohemia. Bull. Geosci. 85 (3), 395–414. https://doi.org/10.3140/ Silurian. Jahrb. Geol. Bundesanst. 129 (2), 291–360. bull.geosci.1204. Kříž, J., Dufka, P., Jaeger, H., Schönlaub, H.P., 1993. The Wenlock/Ludlow Boundary in Stampfli, G.M., Raumer, J.F., Borel, G.D., 2002. Paleozoic Evolution of Pre-Variscan the Prague Basin (Bohemia). Jahrb. Geol. Bundesanst. 136 (4), 809–839. Terranes: From Gondwana to the Variscan Collision. Geological Society of America Lang, W.H., 1937. On the plant-remains from the Downtonian of England and Wales. Special Paper 364. pp. 263–280. https://doi.org/10.1130/0-8137-2364-7.263. Philos. Trans. R. Soc. Lond. B 227 (544), 245–291. https://doi.org/10.1098/rstb. Stampfli, G.M., Hochard, C., Vérard, C., Wilhem, C., von Raumer, J., 2013. The formation 1937.0004. of Pangea. Tectonophysics 593, 1–19. https://doi.org/10.1016/j.tecto.2013.02.037. Lang, W.H., Cookson, I.C., 1935. On a Flora, including vascular land plants, associated Štorch, P., 1995. Biotic crises and post–crisis recoveries recorded by graptolite faunas of with Monograptus, in rocks of Silurian age, from Victoria, Australia. Philos. Trans. R. the Barrandian area, Czech Republic. Geolines 3, 59–70.

154 P. Kraft et al. Palaeogeography, Palaeoclimatology, Palaeoecology 514 (2019) 144–155

Štorch, P., Frýda, J., 2012. The late Aeronian graptolite sedgwickii event, associated po- the peri-Gondwanan shelf in the Lower/Middle Devonian boundary marine deposits. sitive carbon isotope excursion and facies changes in the Prague Synform (Barrandian Foss. Imprint 72 (3–4), 155–160. https://doi.org/10.14446/FI.2016.155. area, Bohemia). Geol. Mag. 149 (6), 1089–1106. https://doi.org/10.1017/ Vavrdová, M., 1984. Some plant microfossils of possible terrestrial origin from the S001675681200026X. Ordovician of Central Bohemia. Věst. Ústř. Úst. geol. 59 (3), 165–170. Tasáryová, Z., Janoušek, V., Frýda, J., 2018. Failed Silurian continental rifting at the NW Wellman, C.H., Edwards, D., Axe, L., 1998. Permanent dyads in sporangia and spore margin of Gondwana – evidence from basaltic volcanism of the Prague Basin masses from the Lower Devonian of the Welsh Borderland. Bot. J. Linn. Soc. 127 (2), (Teplá–Barrandian Unit, Bohemian Massif). Int. J. Earth Sci. https://doi.org/10. 117–147. https://doi.org/10.1111/j.1095-8339.1998.tb02092.x. 1007/s00531-017-1530-5. Wellman, C.H., Steemans, P., Vecoli, M., 2013. Palaeophytogeography of Ordovician – Thornton, I.W.B., Cook, S., Edwards, J.S., Harrison, R.D., Schipper, C., Shanahan, M., Silurian land plants. In: Harper, D.A.T., Servais, T. (Eds.), Early Palaeozoic Singadan, R., Yamuna, R., 2001. Colonization of an island volcano, Long Island, Biogeography and Palaeogeography. Geological Society London Memoirs 38. pp. Papua New Guinea, and an emergent island Motmot, in its caldera lake. VII. 461–476. https://doi.org/10.1144/M38.29. Overview and discussion. J. Biogeogr. 28 (11−12), 1389–1408. https://doi.org/10. Xue, J.Z., Wang, Q., 2011. Fusiformitheca, a new name for Fusitheca Wellman, Edwards et 1046/j.1365-2699.2001.2811121389.x. Axe, 1998, non Bonorden, 1864. Palaeoworld 20 (1), 98. https://doi.org/10.1016/j. Trotter, J.A., Williams, I.S., Barnes, C.R., Männik, P., Simpson, A., 2016. New conodont palwor.2010.12.006. δ18O records of Silurian climate change: Implications for environmental and biolo- Xue, J.-Z., Wang, Q., Wang, D.-M., Wang, Y., Hao, S.-G., 2015. New observations of the gical events. Palaeogeogr. Palaeoclimatol. Palaeoecol. 443, 34–48. https://doi.org/ early land plant Eocooksonia (Upper Silurian) of Xinjiang, China. J. Asian Earth Sci. 10.1016/j.palaeo.2015.11.011. 101, 30–38. https://doi.org/10.1016/j.jseaes.2015.02.003. Vaškaninová, V., Kraft, P., 2016. A unique occurrence of a psammosteid heterostracan on

155