Two New Carboniferous Fertile Sphenophylls and their Spores from the Czech Republic

Two new species of sphenophyllalean strobili with in situ spores are proposed from the Radnice Basin of the western and central Bohemian Carboniferous continental basins of the Czech Republic. Bowmanites brasensis sp. nov. from Břasy (Matylda Mine) and B. pseudoaquensis sp. nov. from Ovčín locality are determined mainly on the basis of their spores, which are about 100 µm in diameter. The thick-walled exine of the miospores is laevigate or sometimes very finely scabrate on the proximal contact area. Spores resemble the dispersed species Punctatisporites obesus. Cones of B. brasensis and B. pseudoaquensis are organically connected with stems having prominent blade leaves and represent a new group of sphenophyllalean strobili.


Introduction
The majority of Carboniferous sphenophylls and their spores are stratigraphically important fossils. Some also have palaeo− ecological importance and can be used in palaeoenviron− mental reconstructions. Carboniferous sphenophylls have been classified based on sterile parts of plants (mainly leaves) for many years. Several authors have proposed a large number of sphenophyllalean species, even though heterophylly is wide− spread. The systematics of "leafy" sphenophyllalean taxa con− sists of several species that are probably synonymous. Most sphenophyllalean cones with different modes of preservation (petrifactions and compressions) have been assigned only to the genus Bowmanites. The main criterion for their classifica− tion is the morphology/anatomy of the cones, the significance of their in situ spores having been ignored for many years. This contrasts with modern concepts of the classification of fossil reproductive organs where in situ spores are as impor− tant in taxonomic diagnoses and descriptions as their parent plants (e.g., Thomas 1970;Opluštil 2004, 2006). Au− thors following this concept have developed a new approach to the classification of Carboniferous sphenophyllalean fruc− tifications based on a combination of morphological/anatomi− cal features of the cones and their in situ spores (e.g., Bek 1998Bek , 2004Bek 2003, 2006;Bek et al. in press). This new systematics represents a more natural classification and recognises seven groups (e.g., Libertín and Bek 2006) characterised by different cones and in situ spores. The current paper adds to our knowledge of a new group of spheno− phyllalean plants. Studies of several specimens of compres− sion strobili of Bowmanites brasensis sp. nov. and B. pseudo− aquensis sp. nov. and slides with their in situ spores reveal a new type of sphenophyllalean spore.

History of research
Parent plants of Punctatisporites obesus−producing spores belong to the genus Sphenophyllum which was erected by Brongniart (1822) to formally accommodate fossil plants formerly included in Sphenophyllites. Presl (1838) was prob− ably the first to describe a compression specimen of a sphenophyllalean cone, as Rotularia marsileafolia. Binney (1871) proposed the name Bowmanites for structureless frag− ments of sphenophyllalean cones, while Seward (1898) erected Sphenophyllostachys for cones of Sphenophyllum. Sternberg (1823) described the sphenophyllalean plants Rotularia and Volkmannia from the Carboniferous of the Czech Republic. Bek (1998) and Bek and Opluštil (1998) were the first to describe in situ sphenophyllalean spores from the Czech Republic. There are two approaches for the subdivision and classification of sphenophyllalean cones. The first divides them into three groups (Jugati, Conferti, and Simplices) based on the number and position of spo− rangia on each sporangiophore (Hoskins and Cross 1943). The second approach was suggested by Remy (1955), who proposed four new cone genera of sphenophylls, Koino− stachys, Aspidiostachys, Tristachya, and Anastachys, based on similar criteria with special attention to the number of sporangia. However, he also included some non−spheno− phyllalean taxa (e.g., Anastachys). Both of these divisions united parent plants that produced monolete, trilete, and trilete operculate (vestispores and Pteroretis) spores in one group or one genus.

Localities, material, and methods
The specimens WBMP−F 82, NMP−E 6124 (1484 in Bek and Opluštil 1998), and NMP−E 6293 are from Ovčín opencast mine while specimens WBMP−F 03760, WBMP−F 01334, and WBMP−F 00188 came from Břasy, Matylda Mine (both Radnice Basin, Czech Republic). The geographic positions of these localities are shown in Fig. 1. Digital photomicro− graphs and negatives of spores are stored in the Institute of Geology, Academy of Sciences v.v.i., Prague, whereas digi− tal photographs of the cones and slides with spores are in the NMP. Spores were recovered by dissolving small portions of sporangia in 35 % hydrofluoric acid for 24 h and in nitric acid (40%) for 24-40 h, then cleared in KOH (5%) for 1 h. All spores were mounted in glycerine jelly for direct micro− scopic study. Some spores were examined with a CAMECA SX100 scanning electron microscope. Photomicrographs were taken using an Olympus C330s digital camera and a BX51 light microscope. The terms used for the descriptions of the in situ spores are the same as those in the latest edition of the Glossary of pollen and spore terminology (Punt et al. 2007). In situ spores were classified according to the system for dispersed spores suggested by Kremp (1954, 1955), Dettmann (1963), and Smith and Butterworth (1967).   (Fig. 2C, E) and from 0.5 to 4 mm wide but thicker at the nodes. The internodes are 2-5 mm long. The narrow, elongate leaves can be divided into three or four segments, each with a prominent sharp tip ( Fig. 2A, D). Leaves are arranged in verticills (Fig.  2E), up to six, deeply divided along single vein. The length of lobes is 2-5 mm. Reproductive organs are terminally borne (Figs. 2B, 3A). The strobili are 40-60 mm long and their width, including bracts, is 5-6 mm. The cone axis is rela− tively narrow, approximately 0.5 mm wide (Fig. 3D). Circu− lar sporangia 1 mm in diameter (Figs. 2B, 3B-D) are con− nected to the cone axis by sporangiophores about 0.2 mm long ( Fig. 3B, C). The surface of the sporangia is promi− nently grooved. Sporangiophores with terminal sporangia lie between the axis and sterile bracts (Fig. 3D). Sterile bracts are 4-5 mm long, hook−shaped, prominently deflected at the area with sporangiophores. Trilete spores are circular to subcircular 88(96)106 μm in diameter. Inner body 75(88)100 μm in diameter. The spores are three−dimensionally pre− served ( Fig. 3E-H). The outer exine layer, probably exo− spore, is almost always broken or is not preserved (Fig.  3E-H). Its thickness is 3-6 μm (Fig. 3I) Description.-Stems are monopodially branched, 1-2 mm wide with internodes 2-8 mm long and 1-3 mm wide (Fig.  6A, B, D). Leaves are 4-8 mm with narrow lanceolate margins (Fig. 6 C) and arranged in whorls (Fig. 4A, B 2 ). Cones are 200 mm long and 4-5 mm wide and possess an apex with sterile leaves. Circular sporangia are about 1.5-2 mm in diameter (Figs. 4A 3 , 5A, G, 6E). Sporangia occur between the axis of the cone and sterile bract on reduced sporangiophores (Fig.  5A, G). The surface of sporangia is finely rugose. Sterile bracts are hook−shaped; the apical margins are slightly wider at the end with rounded tips. Sterile stems are 1.0-2.5 mm in diameter.
Remarks.-All the spores are closely similar and can be identified as Punctatisporites cf. obesus because the sculp− ture of the exine is sometimes very finely scabrate (Fig. 5E, F) and not laevigate as given in original diagnosis of P. obesus (Potonié and Kremp 1954

Discussion of the spores
Dispersed Punctatisporites.-The dispersed spore genus Punctatisporites consists of several different spore types. Some species possess a relatively thin (e.g., P. minutus) or thicker exine (e.g., P. breviornatus). The exine of some spe− http://app.pan.pl/acta53/app53−723.pdf     cies is laevigate (e.g., P. calvus), microgranulate (e.g., P. irrasus), vermiculate (e.g., P. vermiculatus), echinate−spinate (e.g., P. decorus), infrareticulate (P. nervatus), setate (P. setu− losus) or possesses a ridge (P. sinuatus). The smallest spores of Punctatisporites are only about 14 μm in diameter, while the largest can reach 140 μm in diameter. Punctatisporites was proposed by Ibrahim (1933) and emended by Potonié and Kremp (1954) for spores with a variable exine sculpture (laevigate, punctate, microreticulate or microgranulate). For example, Guennel (1958) considered that all species with a sculptured exine (like P. punctatus, the type species of the ge− nus) should be separated taxonomically. Punctatisporites to− day consists of several miospore morphotypes and it is evident that the genus is highly heterogenous and represents an artifi− cial taxon. This presumption is supported by the extremely long stratigraphic ranges of the morphologically simplest spores. The first rare records of spores of this type are from the Silurian, more frequently occuring in the Devonian and be− coming more abundant in the Carboniferous (Bek 1998).
Some dispersed Punctatisporites species are more or less similar to P. obesus, like P. limbatus, P. labiatus, P. pseu− dobesus, P. edgarensis, or P. bifurcatus. Laevigatisporites laevigatus and the Permian genus Callumispora may be also be similar.
In situ Punctatisporites.-In situ spores of the Punctati− sporites−type have been described from fructifications of plant species of different stratigraphic ages and taxonomic positions. The oldest in situ record of similar simple spores was published by Hoeg (1967) from a Devonian member of the Trimerophytophytina. Boureau (1964) mentioned in situ spores of the Calamospora-Punctatisporites−type from a sphenopsid cone (Cheirostrobus pettycurensis). The most abundant Punctatisporites−producing plants were ferns and fern−like plants, mainly genera like Corynepteris, Stauro− pteris, Pecopteris, Scolecopteris, Asterotheca, and Radsto− ckia (Balme 1995;Bek 1998). Similar in situ spores are re− ported also from parent plants of Triassic-Jurassic (Potonié 1962), Cretaceous (Krassilov 1982) and even Eocene (Balme 1995) age. Dispersed species of Punctatisporites are far more numerous than those reported in situ. Some spores of the Punctatisporites−type may even represent ontogenetic stages of marattialean microspores of the Cyclogranispo− rites-Verrucosisporites−type (Zodrow et al. 2006).

Results
The strobili of Bowmanites brasensis and B. pseudoaquensis are morphologically similar to Sphenophyllostachys aqu− ensis Remy, 1955 (see Table 1) but differ mainly in their spore contents. In situ spores isolated from the type specimen of S. aquensis by Remy (1955) are laevigate, thin−walled and correspond with the dispersed genus Calamospora, while in situ spores of B. brasensis and B. pseudoaquensis are thick− walled and are assigned to a different spore genus, Punctati− sporites.
In situ spores of both of the new Bohemian species corre− spond to the dispersed species Punctatisporites obesus. In situ spores isolated from the specimen assigned to B. pseudo− aquensis (former S. aquensis) by Bek and Opluštil (1998) differ slightly in total diameter (120 μm on average) com− pared with spores of Bowmanites brasensis. It is evident that the Bohemian specimens, early wrongly assigned to S. aqu− ensis by Bek and Opluštil (1998), differ from the holotype of S. aquensis and represent a new species.
The cone morphologies of Bowmanites pseudoaquensis, B. brasensis, and S. aquensis are only roughly similar. Sterile bracts of Bowmanites brasensis are distinctly dichotomously divided, but bracts of B. pseudoaquensis and S. aquensis are simple and lanceolate. The angle between the axis of the cone and bracts of S. aquensis is larger than in B. pseudoaquensis. Bracts of S. aquensis possess a prominent S−like shape, while bracts of B pseudoaquensis are straighter and those of B. brasensis curve apically two−thirds of their length from the point of attachment. Sporangiophores of B. pseudoaquensis and S. aquensis are relatively short, undivided and their sporangia are borne terminally. Sporangiophores of B. brasensis are relatively long (2 mm) and bear sub−terminal sporangia (Fig. 3C). Sphenophyllostachys aquensis is reported (Remy 1955) from the Duckmantian of Germany (Schacht Adolf locality) whereas Bohemian specimens are from the Bolsovian (Whetstone horizon) of the Radnice Basin.
There is no evidence of heterophylly comparable to that re− ported in Sphenophyllum tenerrimum and S. myriophyllum. The general habit is similar to S. trichomatosum, but B. bra− sensis does not possess trichome bases of the stem.
Similar laevigate, thick−walled spores have never been reported in situ from any Carboniferous fructifications. Division of Punctatisporites spores into natural groups would be facilitated by a good knowledge of their parent plants and/or an accurate grouping of morphologically similar spore types into a few new independent spore groups/genera (according to their sculpture, diameter and exine thickness). This is needed because Punctatisporites is probably the most variable Carboniferous dispersed spore genus known.
It is possible to divide Carboniferous sphenophylls into seven groups based on their in situ spore types and different morphologies and anatomies of the cones (Libertín and Bek 2006). Spores isolated from Bowmanites brasensis and B. pseudoaquensis do not correspond with any members of these groups and represent a new group of Carboniferous spheno− phyllalean plants. Their special position is based mainly on their in situ spores. This suggests that the previous classifica− tions of sphenophyllalean cones given by Hoskins and Cross (1943) and Remy (1955) need basic revision because these classifications group together plants that produce different spores (e.g., monolete versus trilete) and overlook the signifi− cance of in situ spores. We are currently working on a new classification of Carboniferous fertile specimens of spheno− phylls. This revision will be based not only on the morphology of the cones, but also on their in situ spores, underlining the necessity of collaboration between palaeobotanists and paly− nologists.