Geologia Croatica A new species of Selaginella ( Selaginellaceae ) from the bolsovian ( Carboniferous Period ) of the Zonguldak – Amasra Coal basin , north-western Turkey

Most pteridologists recognise Selaginella BEAUV as the only genus of extant plants in the family Selaginellaceae MILDE that contains about 700, mainly tropical, species (TRYON & TRYON, 1981). Anisophyllous Selaginella-like fossils are also known from the Bolsovian onwards and THOMAS (2005) concluded that they were close enough to the anisophyllous species of extant Selaginella to be included in that genus. However, the presence of three, not two, pairs of leaves necessitated the erection of a new sub-genus, Hexaphyllum THOMAS, 2005. Nevertherless, Selaginella is a rare genus in the Carboniferous with approximately ten named species and even some of these have not been described in sufficient detail. Therefore, it was a great surprise when we found fragments of two tiny twigs of a Selaginella after dissolving a small rock fragment with coalified leaves. This sample was taken from the borehole number H 42 in Amasra during the ICCP 575 meeting’s field excursion in Turkey in 2010.


INTRODUCTION
Most pteridologists recognise Selaginella BEAUV as the only genus of extant plants in the family Selaginellaceae MILDE that contains about 700, mainly tropical, species (TRYON & TRYON, 1981).Anisophyllous Selaginella-like fossils are also known from the Bolsovian onwards and THOMAS (2005) concluded that they were close enough to the anisophyllous species of extant Selaginella to be included in that genus.However, the presence of three, not two, pairs of leaves necessitated the erection of a new sub-genus, Hexaphyllum THOMAS, 2005.Nevertherless, Selaginella is a rare genus in the Carboniferous with approximately ten named species and even some of these have not been described in sufficient detail.Therefore, it was a great surprise when we found fragments of two tiny twigs of a Selaginella after dissolving a small rock fragment with coalified leaves.This sample was taken from the borehole number H 42 in Amasra during the ICCP 575 meeting's field excursion in Turkey in 2010.

GEOLOGICAL SETTING
The sedimentation of the Upper Devonian and Visean marine carbonates changed into terrestrial deposition during the Upper Visean and Lower Namurian in the Bartin-Amasra Basin (Derman and Özçelik, 1993).The Namurian Alacaağzi Formation, (up to 570 m thick in the Amasra coalfield), is formed of sandstone, siltstone and claystone sequences with thin uneconomical coal seams in its upper part (CANCA, 1994;KEREY et al., 1986).The Westphalian Kozlu Formation (Langsettian), is up to 900 m in thickness and composed of conglomerates, sandstones, mudstones and 18 mineable coal seams (CANCA, 1994; Ab STRA CT Shoot fragments of a new species of Selaginella BEAUV are described from the Bolsovian (Carboniferous Period) of Amasra, Turkey.The shoots are heterophyllous with three paired ranks of different sized leaves enabling it to be referred to the subgenus Hexaphyllum THOMAS.The size, shape and epidermal details of the leaves enable it to be differentiated from other Pennsylvanian species and referred to a new species Selaginella amasrae ŠIMŮNEK & THOMAS, sp.nov.This new record extends the early distribution of the subgenus suggesting that it first appeared in eastern Variscan Euramerica and the intermontane basins of central Europe, before spreading into the foreland basins of western Euramerica.KEREY et al., 1986).The younger Karadon Formation (mostly Duckmantian, Bolsovian and Asturian) comprises up to 550 m of conglomerates, sandstones and mudstones, and the lower part of this section contains the four most economical coal seams in the Amasra coalfield (CANCA, 1994).The sediments in the lower parts of the Karadon Formation are grey to dark grey while in the upper parts they are reddish grey in colour.
The subsequent Permian Aritdere Formation contains red coloured conglomerates, sandstones and mudstones and is unfossiliferous.

MATERIAL AND METHODS
A small fragment of black claystone with Cordaites UNGER leaves was taken from the borehole core Amasra, no.H 42, from a depth of 626.5 m (Hema Endüstri a.ş).This sample comes from the Karadon Formation and its age is Bolsovian (Moscovian) (CANCA, 1994).The cuticles were prepared by ŠIMŮNEK using standard methods (KERP 1990;KRINGS &KERP, 1997 andKERP &KRINGS, 1999).The plant remains were released from the rock using concen- trated (38 %) hydrofluoric acid (HF) and then washed in distilled water.The resulting phytoleims were macerated in Schulze Solution (40 % nitric acid with a little potassium chlorate) for 27 hours and then bleached using 2 % potassium hydroxide solution until the whole oxidation products (brown) matter was released.After washing again in distilled water, some of the cuticles were mounted in glycerine jelly for light microscopy.Some leaves were mounted on a metal stub for observation by SEM.

DESCRIPTION
Fragments of the following taxa were obtained by macera- The largest fragment of Selaginella is a small shoot about 7mm long and 2mm broad, while the other fragments show just a few leaves or portions of leaves.Because they are such small pieces prepared by maceration, comparison with other species known as much larger shoots preserved as recognisable compressions is a little more difficult than usual.Nevertheless, there are recognisable lateral, median and ventral leaves on the Turkish specimens, the sizes of which, outlines and epidermal features were studied under the microscope.The lateral leaves depart at about 15 º from the axis and are about 1.2 mm long, 600 μm broad with elongate-acute apices and dentate margins.Epidermal cells are elongated along the leaves, about 40 x 15 μm in size, and stomata are 30 x 20 μm.The median leaves depart at about 10-15° from the axis and are about 950 μm long, 300 μm broad with acute apices and dentate margins in their lower parts.Epidermal cells are elongated along the leaves, about 25 x 15 μm in size, and stomata are 30 x 20 μm.The ventral leaves depart at about 10° from the axis and are about 550 μm long, 200 μm broad with acute apices and entire margins.Epidermal cells are elongated along the leaves, about 25 x 10 μm large.No stomata could be seen.
There are three species of Carboniferous Selaginella shoots that have been described in sufficient detail to be wor-thy of comparison with the Turkish specimens.Selaginella gutbieri (GÖPPERT) THOMAS, S. stachygynandroiodes (GEINITZ) THOMAS and S. zeilleri (HALLE) THOMAS are all known from leaf and epidermal characters.Other species such as Selaginellites elongatus (GOLDENBERG) HALLE and Paurodendron fraiponti (LECLERQ) FRY need re-investigating, while others such as S. cf.leptostachys (GOLDENBERG) THOMAS (BEK et al., 2001) are not known in sufficient detail to make a detailed comparison with the Turkish specimens.
The characters of all four species are summarized in Table 1 showing the differences in leaf size, leaf shape and epidermal characters.The most obvious difference between the new Turkish Selaginella and all the others is its much smaller overall size, with its correspondingly much smaller leaves.Indeed, because of the small size, it might easily be overlooked if preserved as a compression on dark shale.The larger species, Selaginella gutbieri, S. stachygynan droides and S. zeilleri are much more obvious as compressions with their spreading lateral leaves and overlapping median leaves.Extant species of heterophyllous Selaginella form full sized leaves close behind their growing apices, so it is extremely unlikely that the Turkish shoots are parts of a larger plant.The size difference of the shoot and its leaves, together with the relatively tight arrangement of its leaves against the stem, the details of its leaf outlines and epidermal cells lead us to the conclusion that the Turkish Selaginella is a new species.

THOMAS
The new locality extends the early distribution of Carboniferous anisophyllous species of Selaginella to Turkey.This new record appears to suggest that the subgenus Hexa phyllum first appeared in eastern Variscan Euramerica and the intermontane basins of central Europe before spreading into the foreland basins of western Euramerica.The small size of the Turkish Selaginella suggests that many other similar specimens have been overlooked.It remains to be seen if new discoveries will add information that will give a clearer picture of the origins and distribution of the anisophyllous species of Selaginella.
tion: Selaginella sp., Cordaites sp., Neuropteris sp., Eusphe nopteris cf.sauveuri and Eusphenopteris sp.Observations here are restricted to Selaginella.Fragments of Selaginella were mounted on two slides, 550/1-2 (Coll.Nos: ZŠ 467 and 468), that are stored in the collections of the Czech Geological Survey, Prague.The SEM stub with Selaginella leaves is number 63, also in the Czech Geological Survey collections.
Etymology: Named after the Coalfield where it was collected.