Paweł Filipiak

Palynofacies around the Frasnian/Famennian boundary in the Holy Cross Mountains, southern Poland

Abstract Palynofacies have been analysed in two representative Frasnian/Famennian (F/F) localities (Kowala Quarry and Łagow-Plucki trench) in the Holy Cross Mountains, Poland, with the aim of reconstructing sedimentary conditions and palynofloral history over the extinction boundary interval. Leiospheres are the most common palynomorphs. Taxonomically impoverished acritarch assemblages and a low proportion of land-derived material indicate offshore sedimentation in a mid-shelf environment, with some evidence of an earliest Famennian regression. Increased productivity of phytoplankton near the F/F boundary was possibly related to eutrophication of the epeiric seas, thus causing anoxic conditions close to and on the seafloor. No significant changes in palynofacies have been observed through the F/F boundary deposits in these Laurussian shelf basins, in agreement with data from other parts of the Devonian world.

Palynology and Microfacies of Lower Devonian Mixed Carbonate-Siliciclastic Deposits in Podolia, Ukraine

Investigation of mixed carbonate-siliciclastic Lower Devonian deposits have been carried out in the Ivanye Zolote and Ustechko sections in Podolia, Ukraine. Based on palynomorph evidence, the age of the samples studied is late Lochkovian, not older than the NM Oppel Miospore Zone, specifically the Si Lineage Zone. The presence of acritarchs and chitinozoans points to dominantly marine depositional conditions. However, a regressive environmental change to-ward more brackish conditions is indicated by a decrease in the taxonomic diversity of acritarchs in the topmost samples, the simultaneous disappearance of chitinozoans, and an increase in leiosphaerid frequency. Furthermore, evolution of limestone microfacies demonstrates a progressive transition from a shrinking marine basin toward a brackish, storm-af-fected muddy lagoon, manifested by recurrent profusion of impoverished, mostly opportunistic and euryhaline shelly benthos (nuculanid bivalves, leperditicopids and other ostracods, terebratulid brachiopods), chaetetid demosponges and diverse ichthyofauna. The association of plant (mainly nematophytes and some tracheids) and animal (eurypterid, ?scor-pion, and possibly other arthropod) remains points to the presence of nearby Early Devonian wetland vegetation, provid-ing food and shelter for various semi-aquatic and other terrestrial arthropods.

Organic remains of tentaculitids: New evidence from Upper Devonian of Poland

Organic remains of tentaculitids have been recovered during palynological research on archival samples from the Dobrzyca 2 borehole (Western Pomerania). Until now tentaculitids are widely known from their abundant mineralised shells. As organic remains, on the other hand, they have only been known since 2004. The present discovery is currently the second one of this kind found in Upper Devonian strata. The shape and morphology of some recognized tentaculitid organic remains are similar to embryonic and juvenile forms of dacryoconarids belonging to orders Nowakiida and Stylionida. Based on palynomorphs, the age of the two samples investigated has been established as Frasnian, RB and RD local miospore zones.

Putative Late Ordovician land plants

The colonization of early terrestrial ecosystems by embryophytes (i.e. land plants) irreversibly changed global biogeochemical cycles (Berner & Kothavala, 2001; Berner et al., 2007; Song et al., 2012). However, when and how the process of plant terrestrialization took place is still intensely debated (Kenrick & Crane, 1997; Kenrick et al., 2012; Edwards et al., 2014; Edwards & Kenrick, 2015). Current knowledge suggests that the earliest land plants evolved from charophycean green algae (Karol et al., 2001) most probably during Early-Middle Ordovician times (Rubinstein et al., 2010; and references cited therein). They were represented by small nonvascular bryophyte-like organisms (Edwards & Wellman, 2001;Wellman et al., 2003; Kenrick et al., 2012). The oldest fossil evidence from dispersed spores of presumable bryophytic nature is known from aMiddle Ordovician locality (c. 470million years ago (Ma), Rubinstein et al., 2010; Fig. 1) from Argentina (Gondwana palaeocontinent). The dispersed spore fossil record also suggests that the first radiation of vascular plants probably occurred during Late Ordovician times (c. 450Ma, Steemans et al., 2009). However, unequivocal macrofossils of vascular plants appear much later, during mid-Silurian (c. 430Ma, Edwards et al., 1992). This macrofossil evidence comes from the fossil-genus Cooksonia, an early polysporangiophyte (i.e. a plant with bifurcating axes and more than one sporangium), which is considered the earliest vascular land plant (Edwards et al., 1992; Fig. 1). Further advances in knowledge about the origin and early dispersion of polysporangiophytes are needed for a better understanding of the initial plant diversification. Unfortunately, unravelling the initial steps of polysporangiophyte evolution is hindered by gaps in the fossil record of the earliest plants as well as by limitations of inference based on molecular clocks (Kenrick et al., 2012; Edwards & Kenrick, 2015). Assessing the affinities of fragmentary fossils is frequently only tentative. Most often, only partial evidence for land plant nature is visible on fossils of Silurian–Devonian age. Nevertheless, there are numerous examples in the deep-time fossil record of organisms that have been interpreted as early embryophytes even though unambiguous land plant characters were not demonstrated. For instance, Edwards & Feehan (1980) reported on some Silurian terminal sporangia and dichotomous axes interpreted as Cooksonia-type plantswith no evidence for in situ spores nor for tracheids.Wellman et al. (2003) described the first plant mesofossils with in situ spores from the Ordovician (Katian) fossil record, but the morphology of the parent plants remains unknown. More recently, Morris et al. (2011) reported on numerous fragments of LowerDevonian plants with terminal sporangia and dichotomous axes, some of them lacking preserved unambiguous land plant characters. Interestingly, some of the plants illustrated by Morris et al. (2011, pl. VI) appear closely similar to those reported in Fig. 2 (see later). Here, we document an Ordovician (Hirnantian, c. 445Ma) putative plant macrofossil assemblage. The specimens come from an Upper Ordovician locality at Zbrza in the southern Holy Cross Mountains (HCM, central Poland, SW peri-Baltica; Supporting Information Figs S1, S2, see also Notes S1). The fossils occur in mudstones of the uppermost Ordovician (Hirnantian) Zalesie Formation dated by trilobites, brachiopods and palynomorphs (Kielan, 1959; Temple, 1965; Masiak et al., 2003; Trela & Szczepanik, 2009). The age of the plant-bearing sediments is confirmed by acritarchs and chitinozoans (Notes S1). Reported evidence consists of dichotomously branched slender axes, some with terminal discoid or ovoid structures interpreted as sporangia, which could represent the earliest macrofossil occurrence of polysporangiophytes (Fig. 1). The plant fossils described herein are scattered among various fragments of coalifiedmaterial. Two branching axes broken at both ends (3 mm long9 0.1 mm wide and 2 mm long9 0.3 mm wide, respectively; Fig. 2a,b) are attributable to the fossil genusHostinella that includes vegetative isotomously branched axes. Another specimen shows a trichotomous axis division (3.2 mm long9 0.3 mm wide; Fig. 2c), a feature known to occur in some late Silurian–early Devonian plants (Gonez & Gerrienne, 2010a, b). The studied samples also yielded several probably fertile axes. A small, dichotomously branched, slender and leafless stem (1.5 mm long9 0.2 mmwide; Fig. 2d) bears terminal structures interpreted as sporangia (0.4 mm long9 0.3 mm wide; Fig. 2d). The two other fertile specimens are not branched.They consist of a short axis (1.1 mm long9 0.3 mm wide; Fig. 2e) ending either in a horizontally stretched, presumably cup-shaped, structure interpreted as a sporangium (0.8 mm long9 1.1 mm wide; Fig. 2e) or in an ovoid/hemispherical sporangium-like body (1.3 mm long9 1 mm wide; Fig. 2f). Their form, size and structure seem to be close to those observed fromCooksonia pertoni (Fig. 2e; Lang, 1937; Edwards & Feehan, 1980) and C. hemisphaerica (Fig. 2f; Edwards & Rogerson, 1979; Edwards & Feehan, 1980), respectively. Moreover, the specimen illustrated in Fig. 2(d) looks quite similar to the bifurcating axis showing the basal part of a sporangium described by Edwards et al. (2014, Fig. 3f). Within a macerated residue, we found rare trilete spores resembling the Ambitisporites avitus-dilutus (Steemans et al., 1996; Fig. 2g,h), a morphon interpreted as indicative of vascular plants (Fanning et al., 1988; Steemans et al., 2009); however the trilete marks of our specimens are not regularly formed, which casts doubts on their trilete spore nature. Interestingly, there are a variety of Ordovician spores with irregular trilete-like folds, such as Besselia nunaatica (Nøhr-Hansen & Koppelhus, 1988) that are well known from mosses and hornworts. The last important feature shown by our