Rugose Corals Across the Devonian—Carboniferous Boundary in NW Turkey

An uppermost Famennian (Strunian) coral assemblage has been recovered in the middle part of the Yılanlı Formation of the Istanbul Zone (Zonguldak and Bartın areas, NW Turkey). In the Bartın area, the studied fossiliferous interval corresponds to a c. 30 m-thick unit of bioclastic to peloidal wackestone to packstone grading to grainstone and including two stromatoporoid biostromes. In the Zonguldak area, 60 km westward, the bioclastic facies is dominant. The rugose corals are mainly solitary taxa belonging to the genera Campophyllum, Bounophyllum, Amplexocarinia, and ?Metriophyllum, and only one colonial genus occurs: Pseudoendophyllum. This fauna is similar to that documented in Europe. The campophyllids and dibunophyllids are the main component of the uppermost Famennian assemblages in S Belgium, N France, W Germany, NW and S Poland. The endophyllids occur in S Poland, Novaya Zemlya, and in the Ural Mountains. The Istanbul Zone is supposed to be situated in the central part of the Palaeotethys Ocean, along the southern margin of Laurussia during the uppermost Devonian and Carboniferous. The rugose corals indicate some relationship with the eastern part of Laurussia, or that both areas were under a common marine influence at this time. The global Hangenberg event was not recognized in the Turkish localities, except for the disappearance of the corals, occurring less than 19 m below the Devonian—Carboniferous boundary based on the foraminifers. There is no major facies change through the boundary and the first Carboniferous corals (small Uralinia and Caninophyllum) appear 6 m above the D–C boundary. The new species Caninophyllum charli sp. nov. is described from the upper part of the lower Tournaisian.


Introduction
The uppermost Famennian (Strunian) was a transitional period between the slow faunal recovery following the Frasnian-Famennian crisis and the ecological crisis associated with the Devonian-Carboniferous boundary. It was also a period of rapid diversification of corals probably linked with the Strunian transgression prefiguring the Lower Carboniferous high sea level that followed the worldwide low sea level of the Famennian. During this transgressive phase, several events occurred, among which the Hangenberg is the most important because of the associated extinctions. This biotic event is recognised as one the six largest mass extinctions in geological times. The origin of the crisis is still debated but eustatic and climatic changes resulting in perturbations in the carbon cycle are suggested as the main causes (see Kaiser et al. 2008, 2010 andref-erences therein for recent compilation). The Hangenberg event is often associated with the deposition of euxinic black shale in basin and shelf facies, and a common positive shift of δ 13 C carb (Kumpan et al. 2014 for recent review). The crisis strongly affected the marine ecosystems with severe losses within the ammonoids, trilobites, conodonts, ostracods, foraminifers, tabulate, and rugose corals, and the total extinction of the stromatoporoids and placoderm fishes (Kalvoda 1986;Korn 1986;Simakov 1993;Benton 1993;Walliser 1996;Poty 1999;Nicollin and Brice 2004). The modalities of radiation and extinction of rugose corals at the Devonian-Carboniferous boundary were documented by Poty (1999) and Berkowski (2001Berkowski ( , 2002 based mainly on data from Europe, South China, and Eastern Siberia. In the Middle East, uppermost Famennian corals were unknown but shallow water carbonates were documented by Dîl (1975) and Dîl et al. (1976) in the Istanbul Zone (NW Turkey), within the Yılanlı Formation. The recent investigation of Dîl's localities (Dîl 1975;Dîl et al. 1976) yielded an abundant coral fauna and associated foraminifers. The aims of this paper are (i) to document sections covering the Devonian-Carboniferous boundary in NW Turkey and (ii) to describe the uppermost Famennian (Strunian) and lower Tournaisian (Hastarian) rugose corals from these sections. The new data allow a comparison of the faunal assemblage of Turkey with some previously described rugose coral faunas of Eurasia.
In Western Europe, the uppermost Famennian is often synonymised with the term "Strunian". Initially, "Strunian" was used in a time-facies sense (fossiliferous marine carbonate facies overlying the siliciclastics of the Middle-Upper Famennian). The term is currently used in a stratigraphic way only and corresponds to the uppermost Famennian (fourth and last substage of the Famennian) that covers the upper Palmatolepis expansa and Siphonodella praesulcata conodont zones (Conil et al. 1986;Streel et al. 2006). Similarly, the lower Tournaisian substage, defined in Belgium as "Hastarian" and its sequence-, litho-, and bio-stratigraphic identity (Poty et al. 2013) can be recognized in NW Turkey. Since no stratigraphic scheme is available in Turkey, the stratigraphic canvas of Poty et al. (2006), established for Western Europe succession, was successfully applied.  Görür and Tüysüz 2001;Moix et al. 2008;Okay 2008). CCAC, Central Anatolian Crystalline Complex; EAAC, East Anatolian Accretionnary Complex (Sanadaj-Sirjan Block); Lycian Np., Lycian Nappes. B. Geological map of the Istanbul-Zonguldak Zone (modified after Okay et al. 2006) with the position of the Zonguldak and Bartın areas. C. Simplified geological map of the Zonguldak area (redrawn after Hoşgörmez 2007 andCharles 1933) with the location of the sampled sections (G, Gökgöl section). D. Simplified geological map of the Bartın area (redrawn after Tokay 1954) Poty et al. (2006); LS, longitudinal section; MFZ, Mississippian foraminiferal zones of Poty et al. (2006); TS, transverse section.

Geological setting and description of key sections
The Istanbul Zone is classically divided into Istanbul and Zonguldak areas. During the Late Devonian and Early Carboniferous times, the Istanbul Zone was part of the Laurasian southern margin and had been drifting south-ward during the Albian when the Western Black Sea Basin opened (Görür 1988). Its former location was demonstrated by the similarity of the tectonostratigraphic records of the zone with the Moesian terranes (see Görür et al. 1997 and Kalvoda and Bábek 2010 for a recent review). In the Istanbul Zone, the D-C transition is situated within the Trakya flysch series (Özgül 2012 and references therein). In the Zonguldak Zone (Zonguldak and Bartın areas; Fig. 1), the Devonian and Carboniferous carbonate rocks are included in the Yılanlı Formation. The D-C transition is exposed in the Gökgöl section (Zonguldak vicinity) and in the Topluca, Dallıca, and Esenpınar sections (Bartın vicinity).
The Gökgöl section is situated along the road D750 Devrek-Zonguldak, upstream of the Asma hamlet, 4 km south of Zonguldak (41°26'19.28" N 31°50'05.43" E; Fig. 1C: G). The uppermost Famennian is dominated by thick-bedded bioclastic floatstone containing fragments of stromatoporoids, solitary rugose corals (Campophyllum), syringoporids, and Pseudochaetetes. This 3 m-thick fossiliferous horizon (G3) is overlain by a 15 m-thick unit (G7a) composed of pluri-metric (?) massive beds of light dolomitic limestone with no macrofauna (Fig. 2). Several horizons yielded a rich association of foraminifers, including numerous quasiendothyrids indicating the Strunian DFZ7 biozone of Poty et al. (2006). The following 10 m (unit G7b) are dolomitic and non fossiliferous. The G7c unit is dominated by massive light bioclastic limestone (packstone and grainstone) that yielded a foraminiferal fauna typical of the MFZ2 biozone of Poty et al. (2006). The D-C is thus situated within the G7a-c interval (Fig. 2). By comparison with the Topluca section (see below), the boundary should be placed in the lower part of the G7a sub-unit. Unfortunately, the sampling was not detailed enough and the frequent dolomitization often hides the microfossils useful for the boundary identification. The next unit (G8) is marked by the appearance of small black cherts and the progressive darkening of the limestone. The sub-unit G8a (c. 20 m-thick) is dominated by thinly bedded crinoidal and bioclastic limestone (mainly packstone) with brachiopods shells layers and small cherts. The overlying unit shows similar microfacies but the cherts are less frequent and some horizons with corals (Caninophyllum and fragmented syringoporids colonies) were noticed. Its top is dolomitized and capped by an erosive surface. Foraminifers from the G8b fossiliferous level indicate the MFZ3 biozone, i.e., the upper part of the Lower Carboniferous (Fig.  2). The Gökgöl section exposes almost continuously the Tournaisian and Viséan succession (Dîl 1975;Dîl et al. 1976;. The Topluca section is situated 7 km northwest of Bartın town, along a new track created between the Topluca earth pit and the valley road (41°41'10.15" N 32°16'53.54" E; Fig.  1D: T). The section exposes the uppermost Famennian and lower Tournaisian strata near the road to Esenpınar village. The section begins by a thick sequence of greyish coarse-grained dolostone with only ghosts of fossils. The dolomite passes rapidly to bioclastic limestone including two biostromes with stromatoporoids 45 and 60 cm-thick respectively (Fig. 3A). The two levels are separated by c. 8 m of tectonic breccia probably indicating a fault. The biostromes are boundstone made of decimetric lamellar stromatoporoids separated by dolomitic microspar. The solitary rugose coral Bounophyllum praecursor is common in the stromatoporoid facies. More than 80 m of poor outcrop (fault-affected weathered limestone and breccia) separate the biostrome from the rest of the section. After this gap, the facies are bioclastic (packstone-grainstone to rudstone) very rich in rugose corals (Campophyllum; Fig. 3B), stromatoporoids and syringoporids. The foraminifers present in these facies indicate the DFZ7 biozone of Poty et al. (2006). The D-C boundary is situated in the following 25 m that were analysed in detail (Fig. 4). Beds 1 to 10 still contain Campophyllum and stromatoporoids in bioclasticfacies. Beds 11 to 16 still yielded Devonian foraminifers (DFZ7). Beds 17 to 32 are dolomitized and the original facies are not recognizable. Bed 33, less dolomitized, yielded the last Devonian foraminifers (Quasiendothyra; DFZ7). Beds 35-40 yielded only unilocular foraminifers, typical of the lowermost Hastarian MFZ1 biozone. The D-C boundary is placed at the top of bed 33 after the foraminifers. The next unit begins with 4 m of light grey argillaceous nodular limestone containing small black cherts but no corals (Fig. 2). A gap of 12 m separates this unit from the following one, composed of light grey limestone, finely bioclastic with Uralinia simplex, the first Carboniferous coral recorded in Topluca. The next 10 m are massive light-coloured limestone that yielded only fragments of brachiopods.
The Dallıca section is composed of a series of small outcrops along a forestry path north of the Akgöz hamlet (41°40'09.58" N 32°18'34.68" E; Fig. 1D: D). The uppermost Famennian is represented by light-coloured limestone with small colonies of Pseudoendophyllum sp. and cauliflowershaped stromatoporoids. The foraminifers are not diversified but the occurrence of the genus Avesnella allows the identification of the DFZ5-6 biozones of Poty et al. (2006), i.e., the lower part of the Strunian. The quality of the outcrops was not apropriate for logging. The Esenpınar section is also a succession of small outcrops along the road from Esenpınar hamlet to Bartın. The uppermost Famennian crops out approximately 1.5 km west of the hamlet (41°41'13.11' N, 32°15'26.22' E; Fig. 1D: E). The facies are bioclastic and pelloidic and the faunal content includes Campophyllum, syringoporids, and stromatoporoids.

Material and methods
The present paper is based on c. 80 specimens collected in Zonguldak and Bartın areas between 2008 and 2011 and studied in thin section (c. 180 transverse and longitudinal thin sections). The newly collected material is housed at PA.ULg.
Remarks.-According Hill (1981), Campophyllum is the only member of the family Campophyllidae, nevertheless, "Palaeosmilia" aquisgranensis (Frech, 1885) could be included in the same family as it probably evolved from Campophyllum (and has no affinity with the Viséan Palaeosmilia; see Poty 2010). Goldfuss' (1826) type material of Campophyllum flexuosum was considered by this author as Middle Devonian. Schindewolf (1937) and Frech (1885) considered them as Strunian, a view shared by Hill and Jull (1965) in their re-description of Goldfuss' types. Hill and Jull's (1965) paper allowed the definition of the genus to be restrained to Strunian forms. Middle Devonian and Viséan corals attributed to Campophyllum should therefore be reinterpreted. Campophyllum were described is the Namur-Dinant Basin (Belgium, Aachen  Fig. 2). The stratigraphic distribution of some guide taxa is also indicated. vicinity and Avesnois; Poty 1984), Poland (Pomerania, Chwieduk 2005; Holy Cross Mountains, Berkowski 2002) and in the Omolon Massif (Siberia) under the names Protocaninia (Onoprienko 1979a) and Campophyllum (Poty and Onoprienko 1984). Famennian corals of New Mexico, attributed to Campophyllum by Sorauf (1992) show several morphological differences (minor septa not contratingent, short counter septum, complex dissepimentarium) suggesting a distinct genus and possibly in another family. As discussed in Sorauf (1992), these "campophids" are somewhat older (lower Palmatolepis expansa Conodont Zone) than the classic European Strunian Campohyllum. In Europe, Campophyllum appears in the uppermost Famennian (base of Siphonodella praesulcata Conodont Zone) or a little earlier (P. expansa Conodont Zone; Berkowski 2002). From the beginning, Campophyllum shows a surprising morphological plasticity that can be explained by the quick recovery of numerous empty ecological niches after the demise of corals at the Frasnian-Famennian boundary and the very slow post-crisis diversification during the Famennian (Poty 1984(Poty , 2010Berkowski 2002). Unpublished data of Edouard Poty (personal communication, May 2013) indicate the successive appearance of at least six yet unnamed species in a lineage characterized by an increase of corallum diameter and length of septa (Poty 1999). The final species are very large (30-50 mm), counting numerous long septa prefiguring the morphology of "Palaeosmilia" aquisgranensis (Frech, 1885), that probably evolved from Campophyllum at the end of the uppermost Famennian (Poty 2010). Campophyllum and associated genera became extinct at the Hangenberg event preceding the D-C boundary (Poty 1999  Material.-Thirty-six specimens and numerous fragments (65 TS, 20 LS); 24 from the Topluca (Bartın), 7 from Esenpınar (Bartın), and 5 from Gökgöl (Zonguldak), uppermost Famennian.
Description.-The corallum is solitary and cylindrical, up to 15 cm high with a maximum diameter of 25 mm in the calyx. The external wall and parts of the dissepimentarium are often eroded in the large specimens. The mean tabularium diameter is 14 mm (maximum 21 mm). There are 45 septa in average (maximum 60; Fig. 6). The major septa are straight or slightly wavy in the dissepimentarium. They are usually long (up to 3/4 of the corallum diameter) but can be withdrawn or amplexoid in some cases (Fig. 5D, G). Despite their length, they do not reach the axis and leave a free zone of about 5 mm in diameter in the centre of the tabularium. The counter septum usually enters into this central zone. The cardinal septum is sometimes slightly shorter than its neighbours. The minor septa are long (1/2-3/4 of the length of the major septa) and sinuous, particularly in the dissepimentarium. They are contratingent or contraclinant. Some of them are intercepted by second order lonsdaleoid dissepiments. The thickness of the septa is variable, even in one specimen. The thickening occurs mainly in the cardinal quadrants but the counter quadrants are also affected in some specimens. The cardinal fossula is variably marked. Alar fossulae occur occasionally in small sized sections (juvenile stages). The dissepimentarium counts 4-6 rows of concentric interseptal dissepiments (maximum 14 in large specimens). In the latter, the inner rows can be V-shaped and herringbone. The inner row is commonly thickened, particularly in the cardinal quadrants. Some incomplete rows of first and second order lonsdaleoid dissepiments are present in large specimens (Fig. 5M). The external wall is regular and thin. In longitudinal section, the tabulae are usually complete and regularly spaced (Fig. 5J 2 , L). They are typically mesa-shaped, the central part being flat and rising 1-2 mm from the peripheral edge of tabulae. The dissepiments are narrow, often high and Remarks.-In addition to size variation, the variability is extreme in this species and affects all the skeletal elements. The length and thickness of septa can double, even in the same specimen. The cardinal fossula varies from a shallow depression occupied by a long cardinal septum, to an opened fossula edged by curved cardinal-lateral septa and occupied by short and thick septa, and to a long and narrow keyhole-shaped fossula incised in the dissepimentarium. The morphology of the juvenile stages varies from zaphrentoid pattern to amplexoid forms ( Fig. 5D) or stages with radially disposed long septa (Fig. 5K). Also, the dissepimentarium varies from 0 to 20 rows of dissepiments-mainly interseptal but with common lonsdaleoid dissepiments of both orders in large specimens. This plasticity might indicate more than one species but no discrete character allows a clear separation between different forms, all being continuous and all the possible intermediate forms occur. Moreover the quantitative data (e.g., diameter versus number of septa; Fig.  6) form a single continuum. All of them are commonly observed in the topotypic material of C. flexuosum (Edouard Poty, personal communication, May 2013). Further analysis based on the abundant French and Belgian material might refine the definition of C. flexuosum.
The specimens investigated here share with C. flexuosum (Goldfuss, 1826): (i) a long counter septum, (ii) sinuous ("flexuous") septa, (iii) contratingent or contraclinant minor septa, (iv) a narrow dissepimentarium (comparatively to other species, see below). Chwieduk (2005) excluded from C. flexuosum corals with long and thick septa in the juvenile stages, a short cardinal and a long counter septum. However these morphological variations are common within C. flexuosum and do not justify a new species. C. flexuosum has dimensions similar to those of C. cylindricum Onoprienko, 1979b but the latter has straight septa and minor septa less contratingent.
Description.-The corallum is cylindrical, up to 15 cm high and up to 50 mm in diameter. The mean diameter of the tabularium is 20 mm (maximum 36 mm). There are, in average, 54 septa of each order (maximum 68; Fig. 6). The major septa are straight or slightly wavy in the dissepimentarium. They are long and reach the axis of the corallum but leave a septa-free zone 1-6 mm-wide in the central part of the tabularium. The counter septum is very long (up to 5 mm longer than other major septa) and extends up to the axis but without forming a true columella (Fig. 7C 2 ). The cardinal septum is usually shorter than the other septa. The minor septa are long (1/2-3/4 of the length of the major septa) and straight. They are contraclinant or contratingent. Both series of septa are thickened in the juvenile stages. The thickening decreases during the growth of the coral. In mature stages, the septa are thickened in the cardinal parts of the tabularium. The thickening is not symmetrically distributed in the corallum and specimens with septa thickened in only one alar "quadrant" are common (Fig. 7A 1 ). The cardinal fossula is long, larger in its axial part, and edged by thickened cardinal-lateral major septa shorter than the other septa ( Fig. 7C 3 ). In the mature stages, the dissepimentarium counts up to 30 rows of dissepiments: concentric, angulo-concentric, V-shaped or rare herringbone interseptal dissepiments, and some rows of lonsdaleoid dissepiments (Fig. 7B 2 ) that can be naotic. The wall is thin and regular and often eroded. In longitudinal section, the tabulae are complete and associated with numer-  ous densely packed small tabellae. Their shape varies from horizontal, domed to mesa-shaped. Some are concave in the central part and show lateral shoulders (Fig. 7C 4 ). In this case, small tabellae fill the concavity to make the tabularium flatter. The dissepiments are numerous and steeply inclined (70-80°). Two morphologies occur in the same specimen: small globose dissepiments about 1 mm high and long and stretched dissepiments 1-1.5 mm high and 3-5 mm long. There are about 15 dissepiments and 30 tabulae (both complete and tabellae) per centimetre.
Remarks.-The large dimensions, the length of septa and the width of the dissepimentarium are the main characters distinguishing this species from C. flexuosum (Goldfuss, 1826). Nevertheless, the juvenile stages of both species are very similar: major septa thickened and flexuous, minor septa short, short counter septum (compare Fig. 5G and Fig. 7D). For a similar diameter, Campophyllum sp. usually shows a narrower dissepimentarium but this character rapidly changes during ontogeny. Detailed treatment of this form is pending and will be published elsewhere. Suborder Ketophyllina Zhavoronkova, 1972Family Endophyllidae Torley, 1933Genus Pseudoendophyllum Onoprienko, 1979b Type species: Endophyllum nalivkini Gorsky, 1935; uppermost Famennian of Novaya Zemlya, Russia.
Remarks. -Onoprienko (1979b) created Pseudoendophyllum for the corals attributed to Endophyllum Torley, 1933by Gorsky (1935, 1938 in the uppermost Famennian of Novaya Zemlya. As noticed by Berkowski (2002), Gorsky (1935) described his corals as Endophyllum because he could not highlight any difference with the Devonian genus. Nevertheless, no Endophyllum is known between the Frasnian and the uppermost Famennian, so the uppermost Famennian Endophyllum are possibly homeomorphs of the Middle Devonian ones and should thus be considered as Elvis taxa (Berkowski 2001). In Poland, Berkowski (2002) documented two species from the uppermost part of Middle Famennian (Palmatolepis marginifera Zone) to uppermost Famennian (Siphonodella praesulcata Zone).
The origin of the genus should consequently be situated, at least in the Early Famennian. Onoprienko's (1979b) choice to create Pseudoendophyllum is justified if the Middle and Upper Devonian forms have a different origin. Berkowski (2002) proposes two hypotheses for this origin: (i) Pseudoendophyllum evolved from Smithiphyllum by acquiring a cerioid habit; (ii) Pseudoendophyllum is a Tabulophyllum that became colonial (this second option is also favoured by Jell and Hill 1970 for the origin of the Middle Devonian Endophyllum). Tabulophyllum being present in the Famennian (Poty 1984;Berkowski 2002), it might be at the origin of Pseudoendophyllum.
Description.-The colonies are small (10 cm in diameter), fasciculate to sub-cerioid (Fig. 5N). The corallites are cylindrical to sub-prismatic. Their mean width is 16 mm and their tabularium diameter is 9 mm in average (maximum 12 mm). There are 33 septa of each order (maximum 36). The major septa are long but do not reach the centre of the tabularium where a free zone of 1-3 mm large is usually present. They are sinuous or zig-zag, often thick at the base and sometimes up to the tabularium. The cardinal septum is short; the cardinal-lateral septa are also shorter and edge the opened cardinal fossula. The minor septa are long (more than half the length of the major) and enter into the tabularium. They are sinuous and thinner than the major. Some are contraclinant. In the outer part of the dissepimentarium, the major septa appear as septal crests on the wall or the lonsdaleoid dissepiments. All the septa are intercepted by first order (1-7 rows) and second order (3-5 rows) lonsdaleoid dissepiments. The interseptal dissepiments are concentric, V-shaped and herringbone. The wall is thin and regular but usually eroded. In longitudinal section, the tabulae are complete, mesa-shaped or domed, some are depressed axially (Fig. 5Q). The lonsdaleoid dissepiments are 1.5-3 mm long and 0.5 mm high. They are flat and gently inclined in the outer part of the dissepimentarium but smaller (1 mm) and more inclined (60-70°) near the tabularium. The inner row is vertical. There are 12-14 tabulae and up to 24 dissepiments per centimetre. The increase is lateral and non-parricidal. The offsets appear in the peripheral part of the dissepimentarium. The smallest offsets observed are already cylindrical, 3-4 mm in diameter and have less than 20 short sinuous septa (Fig. 5P 1 ). The lonsdaleoid dissepiments appear where corallites reach 4 mm in diameter. Unfortunately, the limited material prevents any blastogenic study of this species.
Remarks.-The Famennian species of Pseudoendophyllum described by Berkowski (2002) are cerioid but the Turkish colonies are fasciculate to sub-cerioid. Two hypotheses can explain this habitus. (i) The colonies are really fasciculate and the present specimen might deserve a distinct generic name. This view was supported by Berkowski (2002) in his review of the present genus as he pointed out the bilateral septal arrangement in some specimens. (ii) The fasciculate habit is due to an effect of sedimentation as documented in cerioid colonies of the genera Lithostrotion, Hexagonaria or Phillipsastrea (Scrutton 1998). This second hypothesis is supported by cauliflower-shaped stromatoporoid, occurring in the same horizon than Pseudoendophyllum colonies, both witnessing irregular or seasonal sedimentation. In that sense, the attribution of the Turkish specimens to Pseudoendophyllum is consequently acceptable.
Pseudoendophyllum sp. was collected in stromatoporoid beds in the Dallıca section (Bartın). The foraminifer assemblage is poor but the occurrence of Avesnella indicates the lower part of the Strunian (DFZ5-6 biozones of Poty et al. 2006 (Frech, 1885). Dibunophyllum being a Viséan genus with well constrained characters, this name was not suitable for the uppermost Famennian specimens.

Diagnosis.-See Berkowski (2002).
Description.-The mean diameter of the corallum is 9.5 mm (maximum 11 mm) and the tabularium is 7 mm wide in average (maximum 9 mm). There are 30 septa of both orders (maximum 32). The major septa are long, straight in the tab-ularium and confluent with the columella. The minor septa are restricted to the dissepimentarium or enter shortly into the tabularium. The cardinal fossula is poorly developed. The axial structure is dibunophylloid or axophylloid, made of an axial plate with 25-30 twisted radial lamellae attached to the axial ends of the major septa. The largest axial structures are not necessarily developed in largest stages. The dissepimentarium counts no more than 2 rows of concentric interseptal dissepiments, several are thickened. The wall is regular. In longitudinal section, the tabulae are domed in the axial part of the tabularium and depressed in periphery. The dissepiments are steeply inclined toward the tabularium.
Remarks. -Chwieduk (2005) created the species Bounophyllum pomeranicum for specimens with dimensions and number of septa less than those of Frech's (1885) species. However, these specimens fall in the variability of the topotypes of B. praecursor (Frech, 1885). Bouno phyllum pomeranicum showing no other distinctive character, it is considered as a junior synonym of B. praecursor. The Turkish specimens fit in the same morphological field of variability, except for their axial structure showing an axial plate much more individualised than in topotypes. This type of variability is, however, commonly observed in taxa with a complex axial structure that may change during the ontogeny or from one specimen to another (e.g., Clisiophyllum, Dibunophyllum, Axophyllum).
Description.-The coralla are eroded and the thickened septa of the cardinal quadrants are usually the only pre-served parts. The approximate diameter of the tabularium varies from 12 to 22 mm, depending on the erosion of peripheral parts. There are 28 septa in average (maximum 30). They are undulating, irregularly thickened but separated from each other, some interseptal dissepiments occupying the space between them. Their axial ends are sharp, except for the cardinal-lateral septa that develop rhopaloid ends. The cardinal septum is shorter and quite undulating. The cardinal fossula is poorly marked. Some interseptal and lonsdaleoid dissepiments are present in the counter side.
Stratigraphic and geographic range.-In S China, U. simplex and U. tangpakouensis are the guide taxa for the lower Tournaisian U. tangpakouensis Zone of Tan et al. (1987), corresponding to the rugose coral RC1γ-RC2 subzones of Poty et al. (2006). In NW Turkey, the species occurs in the light bioclastic limestone of the lower Tournaisian part of the Yılanlı Formation in Bartın area. In equivalent levels of the Gökgöl section, only fragments of tabularium with thickened septa are questionably attributed to U. simplex. The foraminifers associated with the corals indicate the MFZ2 biozone of Poty et al. (2006).

Diagnosis.-See Poty (1981).
Remarks.- Lewis (1929) created the genus Caninophyllum for caniniid corals with septa extending to the axis. This character allows the distinction with Caninia Michelin in Gervais, 1840, Siphonophyllia Scouler in McCoy, 1844and Haplolasma Semenoff-Tian-Chansky, 1974 which all have withdrawn septa. The presence of a loose axial structure is one of the main differences with Bothrophyllum Trautschold, 1879. However, Caninophyllum shows sometimes such an axial structure made of the dilated ends of major septa (e.g., Caninophyllum halkynense Lewis, 1929). The evolution of the genus follows an increase of size and complexity. The stratigraphic succession of species in the Belgian Namur-Dinant Basin exemplified perfectly this lineage. Caninophyllum patulum, the oldest species in Belgium appears early in the Ivorian; Caninophyllum sp. A (Denayer et al. 2011: pl. 4J) characterized the upper Ivorian (Poty 1989); Caninophyllum sp. B (described as C. patulum by Poty 1981) occurs in the Moliniacian; C. archiaci is common in the Livian then finally, C. halkynense appears in the Warnantian. This lineage possibly carries on in the Late Carboniferous where Bothrophyllum Trautschold, 1879 might have evolved from Caninophyllum with axial structure (Poty 1981).
Caninophyllum charli sp. nov.  Diagnosis.-Small Caninophyllum, 30-32 mm in diameter (15-20 mm for the tabularium), having 42-46 septa of each order. Major septa extending to the axis in the juvenile stages but withdrawn in the mature stages, thickened in the cardinal parts of the tabularium. Minor septa rudimentary. Dissepimentarium narrow but complex, constituted of concentric, herringbone and arched interseptal dissepiments. Cardinal fossula conspicuous and opened.
Description.-The corallum is cylindrical, 3-5 cm high. The mean diameter is 32 mm (maximum 38 mm) and the tabularium is in average 17 mm wide (maximum 21 mm). There are, on average, 46 septa of each order (maximum 48). The major septa are long, reaching the axis in the juvenile stages but withdraw toward the periphery during the growth, leaving a central zone of 5-6 mm-wide in the centre of the tabularium (Fig. 8A 2 , C, D). They are thickened but their axial ends are sharp. They bend toward the cardinal fossula in the cardinal quadrants but are straighter in the counter quadrants. The initial thickening occurring in the whole tabularium rapidly decreases during the growth but maintains in the cardinal quadrants in the mature stages. The cardinal septum is shorter and thicker than its neighbouring septa. The minor septa are rudimentary or restricted to the peripheral part of the dissepimentarium. The cardinal fossula is well marked. The dissepimentarium counts 5-12 rows of concentric and herringbone dissepiments and several arched dissepiments in the peripheral part. Second order lonsdaleoid dissepiments occur in some specimens. The inner row of dissepiments is thickened in continuity with the septa (Fig. 8A 3 ). The wall is thin, regular or slightly undulating. In longitudinal section, the tabulae are incomplete, horizontal or domed in the axial part of the tabularium, domed or mesa-shaped in the peripheral part (Fig. 8E). A peripheral gutter develops in the mature stages. The dissepiments are 1.5-3 mm long, 1 mm high and steeply declined toward the tabularium.
Remarks.-The small size and number of septa are diagnostic of Caninophyllum charli sp. nov. and allow its discrimination from C. archiaci (Milne-Edwards and Haime, 1852) and C. tomiense (Tolmachev, 1931). The new species shares its dimensions with C. patulum (Michelin, 1846) but the latter show a larger dissepimentarium usually composed only of concentric and herringbone dissepiments. The septa are less thickened and more withdrawn toward the periphery in C. patulum while its cardinal septum is longer in the juvenile stage. The tabularium is also different: the tabulae are flat or slightly domed in the central part in C. charli but are clearly domed in C. patulum. Poty and Xu (1996) figured two species of small Caninophyllum from the lower Tournaisian Uralinia tangpakouensis Zone of S China. C. cystosum Jiang, 1982 has 41-46 septa for a diameter of 25-35 mm but differs from C. charli by an inconspicuous cardinal fossula and a long counter septum often connected to the cardinal septum. C. shaoyangense Jiang, 1982 is smaller (17 mm and 38 septa of both orders) and has a very large dissepimentarium and septa almost not thickened in the tabularium.

Diagnosis.-See Fedorowski (2003).
Description.-The corallum is 2 mm in diameter, its aulos is well developed and 0.75 mm in diameter. There are 9 septa, thickened at the base, thin elsewhere. The minor septa are not developed. The cardinal fossula is marked by a slight withdrawal of the aulos edge toward the periphery. There are no dissepiments. The wall is 0.3 mm-thick and regular.
Remarks.-The diameter and number of septa are compatible with these of Amplexocarinia rozkowskae Fedorowski 2003, particularly if considered as a juvenile specimen like those figured by Chwieduk (2005). A. rozkowskae Fedorowski 2003 is the sole species of Amplexocarinia Soshkina, 1928 described in the Famennian. The other aulos-bearing genera known in equivalent strata are Syringaxon Lindström, 1882 (Chwieduk 2005) and Neaxon Kullmann, 1965(Semenoff-Tian-Chansky 1988Berkowski 2002). Both have a narrow aulos and thickened septa and wall.
Stratigraphic and geographic range.-Amplexocarinia rozkowskae occurs in the Famennian of Pomerania (Chwieduk 2005). The present specimen was collected, together with Pseudoendophyllum sp., in the Yılanlı Formation in the Dallıca (Bartın). The occurrence of the foraminifer Avesnella sp. indicates the lower part of the Strunian DFZ5-6 biozones of Poty et al. (2006).
Description.-The section has a diameter of 3 mm and there are 16 septa. The latter are thin and fuse together at the centre of the corallum. No septal spine was observed. There is neither fossula nor dissepiments. The wall is thin.
Remarks.-Small solitary undissepimented and columellate rugose corals occur in the Strunian of Germany and Belgium and in equivalent levels in N Poland. They were never described or classified in an accurate way. Chwieduk (2005) classified his specimen as Lophophyllum sp.; Bless et al. (1998) attributed the corals from W Germany to ?Metriophyllum sp. while Denayer et al. (2011) named the corals from Belgium Amygdalophyllum? sp. This taxon seems to be restricted to stromatoporoid facies of the uppermost Famennian. This specimen is similar to the juvenile stages of corals attributed to ?Amygdalophyllum or ?Metriophyllum from Belgium and Germany. These taxa are also similar to juvenile stages of the coral figured by Różkowska (1969) under the name Fasciculophyllum dobroljubovae from equivalent levels of the Holy Cross Mountains (S Poland).

Distribution of corals across D-C boundary
The Strunian (uppermost Famennian) assemblage of NW Turkey is not particularly diversified (in comparison with those of Belgium and Poland), but two successive assem-blages can be recognized. Two assemblages are also known in the Hastarian (lower Tournaisian).
Pseudoendophyllum assemblage.-Pseudoendophyllum sp. and Amplexocarinia rozkowskae are the only rugose corals observed in the Dallıca section. Both are known in S Poland (Berkowski 2002) in level attributed to the "Upper Famennian" (i.e., Upper to uppermost Famennian Sphaenospira Brachiopod Zone of Baliński 1995). Pseudoendophyllum is also known in similar deposits of Novaya Zemlya (Gorsky 1935(Gorsky , 1938. The genus is unknown in Western Europe except for one colony from the Upper Famennian of Aachen area, cited but not figured by Wulff (1922) and destroyed during the war. Poty et al. (2006) did not used Pseudoendophyllum in their biostratigraphic chart but this assemblage can confidently be correlated with the RC0α of these authors. The foraminifer genus Avesnella (diagnostic for the lower Strunian DFZ5-6 biozones of Poty et al. 2006) was identified in the Pseudoendophyllum horizon in Turkey.
Campophyllum assemblage.-This assemblage is dominated by Campophyllum flexuosum and Campophyllum sp. These two species occur mainly in bioclastic facies while the solitary Bounophyllum praecursor and ?Metriophyllum sp. are restricted to the stromatoporoid reefal facies. In the Topluca section, the last Campophyllum occurs c. 25 m below the first Tournaisian corals and the interval between the two occurrences is devoid of macrofauna. Nevertheless, the foraminifers are abundant and the DFZ7 biozone is easily identified up to the D-C boundary. The Campophyllum assemblage can be correlated with the correlated with the rugose coral RC0β subzone of Poty et al. (2006), i.e., the upper part of the Strunian.
Uralinia simplex assemblage.-The first Tournaisian coral occurs in the limestone and dolostone overlying the D-C boundary. The first occurrence of Uralinia simplex in the Topluca section is 6 m above the boundary (based on the last occurrence of the foraminifer Quasiendothyra kobeitusana, DFZ7, and the first unilocular foraminifers, MFZ1). In the Topluca section, Uralinia simplex is common in the lower part of the lower Tournaisian and the highest specimen was collected about 40 m above the base of the substage. Uralinia simplex is the dominant taxon of the assemblage and only one fragment of unidentified zaphrentoid undissepimented rugose coral was noticed. This Uralinia simplex assemblage is correlated with the Uralinia tangpakouensis Zone of Tan et al. (1987) and the rugose coral RC1γ subzone of Poty et al. (2006).
Caninophyllum charli horizon.-In Gökgöl, the lower Tournaisian is relatively poor and only Caninophyllum charli was recognized with some confidence from a single horizon. Crushed specimens were recovered in the Dallıca section of the Bartın area. This occurrence is interesting since in Western Europe, the genus appears in the upper-most Hastarian (Poty 1989;Poty et al. 2006) in the MFZ4 biozone (lower part of Yvoir Formation and equivalents) but seems to appear earlier in Turkey (MFZ3). In Southern China, the genus also appears earlier, in the Uralinia tangpakouensis Zone (Poty and Xu 1996).
Summary.-In NW Turkey, the rugose corals do not allow a precise stratigraphy at the D-C boundary due to a lack of material in the critical interval. Nevertheless, the four assemblages recognized on each side of the boundary are useful locally to estimate the position of the boundary and widely, to establish the correlation with Western Europe, Eastern Europe, and Chinese areas. The D-C boundary was identified by the foraminiferal succession (quasiendothyrids, unilocular, tournayellids) but the value of these markers is under discussion as Quasiendothyra was documented in the Lower Carboniferous (Kalvoda and Kukal 1987;Kalvoda et al. 2015). The Hangenberg event was not recognized in the Turkish localities from a lithological point of view (no obvious facies or colour change, no black shale) and no geochemical data are available for the investigated sections. The extinction event associated with the Hangenberg is marked by the last occurrences of Campophyllum flexuosum and Campophyllum sp. in the Topluca section, about 19 m below the D-C boundary based on the foraminifers. The distribution of the foraminifers is still in a preliminary stage and no data on conodonts are available. The first Carboniferous coral (small Uralinia and Caninophyllum) appear 6 m above the D-C boundary.

Palaeogeographic affinity
Uppermost Famennian (Strunian) rugose corals are not rare and usually thought to form endemic assemblages (Poty 1986(Poty , 1999 but actually, some taxa are more widely distributed than previously concluded. For example, the shallow water assemblages of Western Europe (Belgium, N France, W Germany) contain only solitary rugose corals while the Polish (Kraków area), Uralian (including Novaya Zemlya) and Siberian (Omolon Massif) assemblages contain solitary and a couple of colonial genera (Gorsky 1935(Gorsky , 1938Conil et al. 1982;Poty and Onoprienko 1984) and the coral faunas from South China contain many colonial and solitary genera (Wu et al. 1981;Xu 1996, 1997). Some assemblages dominated by undissepimented rugose corals are also known (Montagne Noire in S France, Semenoff-Tian-Chansky 1988; Moroccan Anti-Atlas, Weyer 2002; German Thuringia and Rheinish massifs, Weyer 1971Weyer , 1989Korn and Weyer 2003;Holy Cross Mountains in S Poland, Różkowska 1969) but are clearly facies-related "Cyathaxonia fauna". The NW Turkey area provides an interesting point of view as it was situated in a transitional biogeographic area during the considered time slice. The Istanbul-Zonguldak Zone was part of the southern margin of Baltica, facing the Palaeotethys Ocean southward and surrounded north-, eastand west-ward by a carbonate shelf (Golonka 2007 ; Fig. 9).
The compilations of data available in literature led to the building of a database of rugose coral genera occurrences in the uppermost Famennian. A cluster analysis was conducted on this presence/absence database (see SOM: table 1, Supplementary Online Material available at http://app.pan.pl/SOM/app61-Denayer_SOM.pdf) using the paired Simpson coefficient and a bootstrap replicates value of 10 000. The resulting cluster (Fig. 10) shows three clusters: one containing only the New Mexico assemblage (Sorauf 1992) which is based on the single Percha Shale Fauna and is not very well constrained stratigraphically (lower Palmatolepis expansa Conodont Zone, i.e., Upper Famennian; Sorauf 1992). This N American Province forms an outgroup to all the other faunas. A second cluster unites Asian localities (Armenia, S China, Vietnam, Tibet, and NW Australia) and corresponds to an Asian Palaeotehyan Province (Asian margin of Gondwana). The third clade groups all the other localities. In the latter, one sub-cluster is clearly separated and include the shallow-water assemblages of the European Palaeotethyan Province while the three localities characterized by their "Cyathaxonia fauna" of deeper facies are grouped in two branches. The Namur-Dinant Basin (Belgium, N France, W Germany), Sudetes and Kraków area (S Poland), Pomerania-Rügen (NW Poland and NE Germany) co-occur in this cluster, together with Novaya Zemlya, the Siberian Omolon Massif, and NW Turkey. The Western and Eastern Europe Provinces of Dubatolov and Vassiljuk (1980), Fedorowski (1981), and Sando (1990) are not clearly separated in the cluster but the distribution of the taxa shows clearly two major provinces: the European Palaeotethyan Province ("Campophyllum fauna"; Figs. 9, 10) in which most shallow-water carbonate localities are characterised by the genus Campophyllum; and the Asian Paleotethyan Province ("Cystophrentis fauna"; S China, Tibet, NW Australia, Vietnam, Armenia), where the genus Cystophrentis is diagnostic. The Istanbul Zone of NW Turkey belongs to the European Palaeotethyan Province and shares the genera Campophyllum, ?Metriophyllum, and Bounophyllum with the Namur-Dinant Basin and Pomerania-Rügen (both in the Western Europe Province of Dubatolov and Vassiljuk 1980;Fedorowski 1981;Sando 1990); and the genera Amplexocarinia and Pseudoendophyllum with the Sudetes, the Ural Mountains, and Novaya Zemlya (eastern part of Laurussia, Eastern Europe Province of Dubatolov and Vassiljuk 1980;Fedorowski 1981;Sando 1990). A "mixed" influence is noticed and may result of an overlapping of the two palaebiogeographic provinces or from convergent dispersal paths in link with oceanic currents. Unfortunately, the poor stratigraphic resolution and the lack of any palaeoceanographic model prevent any precise reconstruction. This similarity may also be due to a geographic closeness of the Istanbul Zone to the considered areas (S Poland, Ural Mountains) situated on the margin of Laurussia at this time. Tari et al. (2012) suggest a closer Fig. 9. Palaeogeographic occurrences of uppermost Famennian (Strunian) rugose corals (modified after Chwieduk 2005, map after Golonka et al. 1994). 1, Omolon Massif (E Siberia); 2, Novaya Zemlya; 3, Istanbul Zone (NW Turkey); 4, Kraków, Holy Cross Mountains and Sudetes (S Poland); 5, Pomerania-Rügen area (NW Poland and NE Germany); 6, German Kulm area (Thuringian and Rheinish massifs); 7, Namur-Dinant Basin (S Belgium, French Avesnois, German Aachen area); 8, Montagne Noire (S France); 9, Anti-Atlas (Morocco); 10, Xinzang (Tibet); 11, Transcaucasus (Armenia); 12, Hunan and Guizhou (S China); 13, Viet-Nam; 14, NW Australia; 15, New Mexico. proximity in positioning the Moesian Terranes and Istanbul Zone close to the Bohemian Massif but this view is not constrained for post-Silurian tectonostratigraphic features.
The similarity of the Omolon Siberian fauna with those of Western Europe is surprising but apparently they are congeneric and have a common origin as it is unlikely that numerous Siberian corals were homeomorphs of the European ones. The occurrence of these taxa as far as the Siberian Omolon might be explained by dispersal ways along existing palaeo-currents. A re-investigation of the uppermost Famennian fauna of Novaya Zemlya and perhaps of the one from the Urals Mountains may contribute here but review of those faunas is still pending. Similarly, the present stage of knowledge of uppermost Famennian rugose corals from central Asia is extremely limited (Simakov 1993). Uppermost Devonian carbonate facies are documented in Kazakhstan, Kirghizistan, Tarim, and Turan (see Soshkina 1960;Streel 2001;Nicollin and Brice 2004, and references therein) but their coral fauna remains unknown. Armenia is the only region of the southern Palaeotethys with a record of the uppermost Famennian coral fauna (Papojan 1975(Papojan , 1977 though questioned by Rodríguez and Liao (2003). No Strunian corals were described from the Turkish Taurides, the Iranian and Afghan blocks.
The lower Tournaisian assemblage, composed of only two, widely distributed genera (Caninophyllum and Uralinia) does not allow any accurate palaeobiogeographical analysis.

Conclusions
The uppermost Famennian (Strunian) coral assemblages of Bartın and Zonguldak is dominated by the solitary genera Campophyllum and Bounophyllum, associated with the colonial genus Pseudoendophyllum and the undissepimented genera Amplexocarinia and ?Metriophyllum. The occurrence of the first two genera indicates a similarity of NW Turkey with the Namur-Dinant Basin (Belgium, N France, W Germany) and Pomerania-Rügen (NW Germany, NE Poland) while Pseudoendophyllum indicates an affinity with the Sudetes (S Poland), Novaya Zemlya and the Ural Mountains. All these taxa disappear before the D-C boundary as an effect of the Late Devonian Hangenberg event, while the first Carboniferous coral appear 6 m above the boundary. Nevertheless, the classic facies associated with this global event (black shale) are lacking in the investigated sections in NW Turkey. This can be explained by the shallow -water settings of the studied areas. The proximal position prevented the shelf being reached by the transgressive euxinic water body. Similar situations were documented from other shallow-water sections (e.g., classical sections in the Namur-Dinant Basin, Azmy et al. 2009; Trolp section in the Graz Palaeozoic, Kaiser et al. 2008; Lesnílom section in the Moravian Karst, Kumpan et al. 2014).