Carboniferous auloporids from the Iberian Peninsula : palaeocology , diversity , and spatio-temporal distribution

Auloporid corals are common in the Palaeozoic and very frequent in the Carboniferous buildups of the Iberian Peninsula. The aim of this study is to analyze the diversity of these corals through a taxonomical recognition of the species and morphotypes that occur in the Iberian Peninsula. Eighteen sections have been sampled between the Ossa-Morena (Mississippian) and Cantabrian (Pennsylvanian) zones dated as upper Viséan to early Kasimovian. In addition, other localities where auloporids occur and are cited in the literature have been also used for this study. The taxonomical identification has been carried out using the criteria proposed by Tchudinova (1980) with little modifications. Thus, eighteen morphotypes and two species belonging to nine nominal genera have been identified (Multithecopora sp. A-H, Syringopora sp. A-B, Aulopora sp. A-B, Cladochonus sp. A-B, Syringoalcyon sp., Roemeripora sp., Sinopora sp., Mastopora? sp., Multithecopora hontoriense and Neomultithecopora cantabrica). Through a classical microfacies study, the environments where the auloporids lived have been identified, as well as the growth patterns and the features of sedimentation. Finally, a preliminary biostratigraphic range chart for the Carboniferous auloporoids from the Iberian Peninsula has been achieved. .


Introduction
Auloporida Sokolov, 1947 is an order of tabulate corals that are very abundant during the Palaeozoic Era.Their dis-tribution ranges from Early Ordovician to Late Permian (Hill, 1981).Auloporids are both primary and secondary builders in the Carboniferous and had an important role along with the algae and others corals in the development of reef limestones (Said et al., 2010;Poty, 2010;Aretz and Herbig, 2010).Wahlman (2002) stated that auloporoids are closely related to chaetetids in his chaetetid-buildups and Minwegen (2001) described the same relationship in the buildups of the Cantabrian Zone, referring to this association as 'chaetetid-coral reef mounds' (Korallen-Chaetetiden-Reefmounds).
Although this group is common in the record, there are few palaeontological studies on Carboniferous auloporids in the Iberian Peninsula.In a general way, this group has been frequently cited, but not described, in palaeontological and geological studies of the Carboniferous of the Iberian Peninsula as auloporid, syringoporid or tabulate corals.
This article represents a compendium of the variety and diversity of Carboniferous auloporid taxa found in the Iberian Peninsula, and the different type of facies and environments in which they grew.The stratigraphic distributions as well as the growth-patterns used by auloporid corals are also objectives of this paper.An exhaustive sampling and identification of the auloporid corals of the Iberian Peninsula in eighteen sections was made to achieve this goal.These sections are spread through the Ossa-Morena (Mississippian) and Canta-through the Ossa-Morena (Mississippian) and Cantabrian (Pennsylvanian) zones (Fig. 1) dated as late Viséan to early Kasimovian.Additionally, other information obtained from the literature is also included in this work.The criteria used for the identification and characterization of the genera were those proposed by Tchudinova (1980) and are analysed below.
Within the Betic Cordillera, auloporid corals were cited by Herbig (1984) in the Marbella Conglomerates, which are a subunit of the Malaguide Complex, Málaga (Spain).The auloporids occur within post-Viséan carbonate pebbles.
Numerous outcrops yielded auloporoids in the Pennsylvanian (Cantabrian-Zone).Winkler Prins (1971) described the type section of the Valdeteja Formation, in the Barcaliente Valley, León (Spain) and found some tabulate corals, citing Cladochonus sp. and Paleofavosites sp.Later Eichmüller (1985) described additional sections of the Valdeteja Formation and found numerous samples of a syringoporid coral that was classified as Sinopora.Recently, Villa et al. (2001) analyzed the biostratigraphic sequence of this section and described some facies containing auloporid corals.van de Graaff (1971a) cited small colonies of auloporid corals in growth-position related to chaetetids in the Piedrasluengas Limestone, Palencia (Spain).
van Loon (1971) mentioned syringoporoid corals together with other fossil remains in the Pando Limestone section, at the Pando Pass and in the road to Prioro, León (Spain).Later, Fernández and Barba (1992) identified auloporoid corals in the Pando Pass.
The only taxonomical study on auloporids in the Spanish record was presented by Rodríguez and Ramírez (1987).These authors described the taxonomical characteristics of two genera and three new species of auloporids that occur in the La Playa de la Huelga section, Asturias (Spain) and interpreted the environments of growth.Later, this section was studied by Minwegen (2001), who identified the same genera.Similarly, the transect of San Antolín-La Huelga was described by Bahamonde et al. (2008), who also recognized syringoporid corals.Minwegen (2001) studied the microfabrics and building organisms dominant during the Carboniferous in several sec- Z. and South Portuguese Zone, S.P.Z.) Modified from Colmenero et al. (2002).
tions of the Cantabrian Zone as indicated above.This author recognized auloporid corals associated with chaetetids in the Villanueva section, Asturias (Spain).Likewise she recognized syringoporoids in the Piedrasluengas limestone as well as Neomultithecopora in the Fuente De section, Cantabria (Spain).The Fuente De section (sensu Minwegen, 2001) was also studied by Martínez-Chacón et al. (2001) and Merino-Tomé et al. (2009), who identified the genus Neomultithecopora, forming small buildups associated with chaetetids, in Cantabria (Spain).Rodríguez et al. (1997) identified some taxa of rugose corals in a section near Ribadesella town, Asturias (Spain), where numerous incrustations of auloporid corals occur on the rugose coral skeletons.Coronado and Rodríguez (2009) recognized syringoporoid corals in the algal-mounds of Cosgaya Formation in Cantabria (Spain) where they occur associated with calcareous algae, chaetetids and rugose corals.Corrochano et al., (in press) found syringoporid corals in the Lena Group within the Levinco Formation, León (Spain) and Corrochano et al. (2009) identified syringoporid corals in the Bachende Limestone in León (Spain) also included in the Lena Group.

Geological settings
The outcrops sampled belong to the Carboniferous rocks of the Iberian Peninsula (Fig. 1).These materials crop out mainly in the Iberian Massif (Lotze, 1945;Julivert, 1971), which occupies almost half of the Iberian Peninsula and corresponds with the European zone of the Variscan Belt.There are additionally a number of smaller Carboniferous outcrops, separated by a Mesozoic and Cenozoic cover, exposed in the Iberian Range, Pyrenees, Catalonian Coastal Ranges, Minorca and Betic Cordillera (Colmenero et al., 2002).See figures 2 and 3 for the location of the eighteen studied and sampled sections in the Ossa-Morena and Cantabrian Zones of the Iberian Massif.

Ossa-Morena Zone
The Ossa-Morena Zone is located in the southwestern part of the Iberian Massif, and contains two marine Mississippian basins: the Guadiato Area and the Los Santos de Maimona Coal Basin (Wagner, 2004).Nine sections have been sampled in both basins.
The Guadiato Area is situated in Córdoba province and is a large and complex area in SW Spain (Fig. 2) that comprises Mississippian siliciclastic and limestone rocks.It is divided into three bands (Cózar and Rodríguez, 1999): 1) Fresnedoso Unit, composed mainly of Viséan siliciclastic rocks, 2) San Antonio-La Juliana Unit, composed of Serpukhovian siliciclastic and limestone rocks, and 3) Sierra del Castillo Unit, composed mainly of Viséan limestone rocks.Most palaeontological and stratigraphical studies were focused on the Viséan units.This is especially marked for studies on rugose corals, (Rodríguez 1985;Rodríguez and Falces, 1996;Rodríguez et al., 2001;Rodríguez and Somerville, 2007;Gómez-Herguedas and Rodríguez, 2008).
Only two sections (Los Santos de Maimona and Cerro Almeña) have been sampled in Los Santos de Maimona Coal Basin that is located in the Badajoz province, between the towns of Los Santos de Maimona, Fuente del Maestre, and Feria.The Carboniferous outcrops form a narrow strip 11 km SE-NW and a width of 1 to 3 km, NE-SW (Fig. 2) and is formed by siliciclastic and carbonate materials, and small volcanic bodies, with a Mississippian age (Rodríguez et al., 1992).

Cantabrian Zone
The Cantabrian Zone is the most northern part of the Iberian Massif (Lotze, 1945), located in the north-west of the Iberian Peninsula.In this area, five zones can be distinguished from a structural point of view, with boundaries set by major thrusts.These are, from west to east: Fold-and-Thrust region (Somiedo-Correcillas, Sobia-Bodón and Aramo units), Central Carboniferous Coal Basin, Thrust Region (Ponga Unit), Picos de Europa Unit, and Pisuerga-Carrión Unit (Fig. 3).Overall, they show a vergence towards the east or the north, with the western units overthrusting the eastern ones.The Pisuerga-Carrión Region or Unit, in the innermost part, is overthrusted by all the surrounding units.

Material of study and methods
Eighteen sections have been sampled searching for auloporid corals.The sampling consisted in the collection of complete colonies, fragments of colonies or fragments of corallites in facies associated with buildups in all of the sections, except in Ribadesella.Ten solitary rugose corals were sampled in this section, because auloporid corals only occur encrusting the rugosans.520 thin-sections of auloporid corals have been prepared to study the inner characters.The specimens from Ribadesella were partly covered with marls and clays.For this reason, ten corals were cleaned with an 8% sodium hexametaphosphate solution during 18 hours to remove the sediment.Later, three thin-sections were made, two of them to observe the inner tion has been dated from the microfauna as late Viséan (Brigantian).The Fuenteobejuna section is 140 m thick, mostly composed of limestones, shales and polymictic breccias in the upper part.The section has been dated from microfauna and the microflora as late Viséan (late Asbian to early Brigantian).San Antonio section consists of limestones interbedded with shales and marls.The limestones are wackestones and grainstones.The section has been dated from the foraminiferal assemblage as early Serpukhovian (Pendelian).The facies that yielded corals are bioclastic limestones that are irregularly distributed in the olistoliths.They are coarse grained and corals are related to a diverse assemblage of invertebrates and algae.The original environment for those sections was open marine, shallow, agitated water (Cózar and Rodríguez, 1999).
Sierra de la Estrella.(Sierra del Castillo Unit).Described and figured by Cózar et al. (2003).It consists of a 234 m thick succession of bioclastic and massive limestones with interbedded marls.The auloporids from Sierra de la Estrella occur in well-bedded biostromal limestones at the top of microbial mounds.They represent the capping beds of the mounds, when they reached shallow waters.The section has been dated from foraminiferal assemblage as Zone 15 of Mamet, 1974 (middle part of the late Viséan, Asbian).
El Collado.(Sierra del Castillo Unit).Described and figured by Cózar (2004).This section comprises more than 150 characters.In addition, some colonies have been cut and polished to observe the growth stages of the colonies.

Localities
The sections mentioned in this chapter have been described in detail in previous papers.Consequently, we will not describe them in detail, but will provide short reports on their most representative lithologies and palaeontological content.Temporal distributions of sections are displayed in Fig. 4.
Antolín.(Sierra del Castillo Unit).Described and figured by Cózar and Rodríguez (2000).This section comprises limestone debris 15 m thick in a mainly siliciclastic rhythmic sedimentation.It is typical from proximal turbidites.This section has been dated as late Viséan (Asbian-Brigantian).The reworked limestones originated in patch reefs located in the border of the talus (Rodríguez and Rodríguez-Curt, 2002).
The section has been dated as late Viséan, zone 15 (Asbian).Auloporoids in Los Santos occur in well-bedded biostromal limestones that have been regarded as a reef-flat (Rodríguez, 1996).They are one of the main building organisms together with gigantoproductid brachiopods and rugose corals.
Cerro Almeña.(Los Santos de Maimona Coal Basin).Described and figured by Rodríguez et al. (1992).It consists of 90 m of alternating limestones, marly limestones and shales.This section has been dated as late Viséan, Zone 15 and 16 (Asbian-Brigantian subtage).Well-bedded to massive bioclastic limestones contain common reworked fragments of auloporoids and some entire colonies at the top of the beds.They lived in calcareous shoals and are accompanied by a diverse assemblage containing different invertebrates, foraminifers and algae.Este de Camasobres: Located in the Casavegas Syncline and corresponds with a small section described by Boll (1985) where abundant rugose corals occur with auloporids and chaetetids.It is Middle Moscovian (Kashirian-early Podolskian horizons) in age.

Cantabrian
Pico Guillermo: Located in the Redondo Syncline.It is a large calcareous olistolith that was described by van de Graaff (1971b) and contains small colonies of auloporid corals in growth position.It is Middle Moscovian (Kashirianearly Podolskian) in age.
Prioro limestones (Pando Formation, Esla Nape): The synorogenic sediments of the Esla Nappe form a succession that exceeds 5 km in thickness in some sectors of the nappe, but generally presents strong changes of thickness, some discordances and lateral changes of facies, as a consequence of the synsedimentary tectonic activity (Alonso, 1989).In the first stage (Bashkirian-Moscovian) the succession has a marine character with deposits of talus (turbidites, olistostromes, shales with pebbles, etc).In this succession, a carbonate lithosome denominated as the Mesao Limestone (van Loon, 1971) is conspicuous.It consists of an alternation of limestones and calcareous mudstones.Bioclastic limestones occur as well as biogenic banks.The biogenic banks are mainly constructed by algae, but corals, brachiopods, crinoids, and fusulinids are almost always present.The bioclastic limestones consist mainly of transported crinoidal fragments, but brachiopods, corals, fusulinids, and even plant remains occur as well.These materials were dated as from fusulinid assemblage as Westphalian C (early Podolskian) by van Loon (1971).
The biogenic banks have been sampled for this study both in the south flank and in the north flank of the Pando Syncline where the thickness of the limestones is much greater.
Playa de la Huelga (Calizas del Cuera, Picos de Europa Unit): This section is exposed along the cliffs of eastern As-is exposed along the cliffs of eastern Asturias from San Antolín Beach to the village of Hontoria.Villa (1995) dated the levels sampled in this work as early Podolskian -late Myachkovian.Rodríguez (1984) studied the coral faunas, mainly focused in the Rugosa specimens.In a later taxonomical study focused in tabulates, Rodríguez and Ramírez (1987) described three new taxa that occur in the Playa de la Huelga section.Two cerioid-phaceloid forms assigned to Neomultithecopora cantabrica and N. submassiva, and a phaceloid-bushy form denominated as Multithecopora hontoriense.The Pennsylvanian materials that provided the subject of the study (interval of latest Podolskian or earliest Myachkovian age) are composed of ca. 100 m of massive Eichmüller (1985) described different sections and outcrops of Valdeteja Formation and identified mounds built by calcareous algae and reef mounds containing the auloporoid coral Sinopora sp.
Las Ilces (Cosgaya Formation, Pisuerga-Carrión Unit).Described and figured by Coronado and Rodríguez (2009).It consists of a calcareous section 35 m thick, composed of limestones, which occasionally alternate black shales and marls.The Cosgaya Formation is composed of bioclastic limestones that show abundant algae and corals and locally form mounds (bioherms?).Those mounds are conspicuous at Las Ilces Section.Auloporoids are common in the mounds and in the surrounding facies.The age of the sections was established by fusulinids as late Bashkirian (Coronado, 2008).
Piedrasluengas (Piedrasluengas Formation, Pisuerga-Carrión Unit).This section comprises 300 m of limestones and marls.The Piedrasluengas Limestone, as was first defined by van de Graaff (1971a), has a early Moscovian age (Vereiskian-Kashirskian), and provides a facies model for most of the Carboniferous limestones in the Cantabrian Mountains.A boundstone of auloporoids and chaetetids has been identified in the level 16 of van de Graaff (1971a), which Mingewen ( 2001) denominated as a biostrome of chaetetids with syringoporids and rugose corals and which was sampled for this study.
Ribadesella section (Calizas del Cuera Formation, Picos de Europa Unit).This section was first described by Rodríguez et al. (1997) and Fernández (1995).In this quarry subhorizontal marls and limestones crop out.The section begins with 8-10 m of silty limestones and marls containing common dissepimented solitary and colonial Rugosa and chaetetids, and scarce auloporids.This interval is overlain by 10-12 m of massive well-bedded limestone containing less abundant corals, which extends to the top of the quarry.Chaetetids are usually represented by large colonies encrusting brachiopods, rugose corals and tabulate corals.Most of them show a subspherical shape.Auloporids were less abundant and usually grew on lateral surfaces of large solitary corals whereas the rugose corals are very abundant and show little or no transportation.The presence of fusulinids in these beds establishes an Early Moscovian age (Rodríguez et al., 1997).
The Vergaño Formation (Pisuerga Carrión Unit) was defined by van de Graaff (1971b) as having a lower part of cross-stratified sandstones-shales with thin interbedded layers of mudstone and sandstone, limestones, and a turbidite bed.Three members of limestone can be recognized in this formation, Socavón Limestone (Podolskian), Cotarraso Limestone (Podolskian-Myachkovian) and the Sierra Corisa Limestone member (Myachkovian).These limestone members form three superstructures denominated as the Casavegas Syncline, Redondo Syncline and Castillería Syncline (Wagner et al., 1983;Wagner 2009).
van de Graaff (1971b) described the facies from the Vergaño Formation and mentioned the presence of auloporid cor-zone range from early Bashkirian to late Moscovian in age.The inclusion of the Morra de Lechugales section extends the record to early Kasimovian.
In addition, syringoporoids cited and figured in the Picos de Europa Unit, at Morra de Lechugales section in Cantabria province (Minwegen, 2001;Martínez-Chacón et al., 2001;Merino-Tomé et al., 2009) have been also identified from the bibliography.The specimens sampled in the Cantabrian and tabulae, together with the corallite diameter, lumen diameter, and their relationship (diameter/lumen), which helps in the identification of some genera such as Multithecopora and Sinopora.The frequency or space between corallites, as suggested by Nelson (1977), is an acceptable criterion for use in Syringoporidae, but not in Multithecoporidae and Sinoporidae, because these families show plasticity in growth and the substrate and environment control the growth of the colonies.The morphology of the colony and the morphology of the corallite only have been considered for the Auloporicae taxa.The kind of septal spines used by Tchudinova (1980) are also used in Scleractinian corals and compiled by Hill (1981).However, in our opinion, this criterion could cause some problems in the classification of tabulate corals.For this reason, we use quantitative criteria (abundant, common or scarce), distribution (sparse, in rows or random) and form (acute or blunt) to describe the septal spines.Occasionally, septal spines are very scarce or absent, but the wall presents undulations in the sclerenchyma as septal projections.Sando (1984) undertook a biostratigraphic study on syringoporid corals from the Western Interior Region, USA and he grouped all the syringoporoids in morphogroups.In the absence of previous taxonomical studies, this methodology has been used in this study, subdividing the genera into morphotypes.Due to the plastic morphology and growth habit of auloporidae, these morphotypes may be species or subspecies (ecophenotypes) or groups of species, and need to be analyzed deeper in the future.
The Carboniferous auloporids of the Iberian Peninsula include nine nominal genera and have been divided into 18 morphotypes and two species, which are based on the morphologic criteria documented above (Table 1).
Multithecopora is the most frequent genus in the Iberian Peninsula.We have identified four morphotypes in the Ossa-Morena Zone: Multithecopora sp.A, sp.B, sp.C and sp.H.
Multithecopora sp.A shows a larger size than the other Mississippian morphotypes of Multithecopora (avg.1.96 mm -range 1.47-2.85mm in diameter; Table 1) and presents well developed septal spines, which show acute morphology (Fig. 5).This morphotype is present in five sections of the Ossa-Morena Zone (Antolín-1, Sierra de la Estrella, Fuenteobejuna, Los Santos de Maimona and El Collado sections) ranging in age from middle-late Asbian to early Brigantian.

Systematics and classification
There are no useful common criteria to establish the main features for the auloporid taxonomy to different levels.Those features depend on the subjectivity of the author and the superfamily involved.In Auloporicae the most commonly used criterion is the general morphology, the growth habit and, to a lesser degree, the presence and morphology of tabulae and septal spines.In Syringoporicae, more diverse criteria have been used.Nelson (1977) used four parameters in the taxonomy of syringoporid corals; two of which are the corallite diameter and the frequency of corallites (number of corallites that occur within a certain area).This author suggests that these parameters are very important in defining species and that both are, more or less, independent of the environment.Nelson (1977) suggests also two other parameters, the type of tabular pattern and the wall thickness, which are significant in defining genera.Other authors, such as Nowinski (1991) and Niko (1998), have employed the frequency or distance between corallites.Tchudinova (1975), Sando (1984) and Nowinski (1991) used not only the corallite diameter and the distance between corallites, but also the wall thickness, diameter of connecting tubes, distance between connecting tubes, distance between tabulae, diameter of axial canal or lumen and the amount of septal spines.These additional characters also were used by Rodríguez and Ramirez (1987) along with the diameter of corallite and thickness.These criteria could be used in those genera that present abundant tabulae and connecting structures, but cannot be used as a systematic feature in all auloporid genera.Tchudinova (1980) presented a study on the morphogenesis of Syringoporidae, which shows a series of characters that occur in different genera through time.These are: microstructure of corallite wall, presence of lamellar or fibrous sclerenchyme and presence of septal spines, connecting elements and tabulae.
In this study we follow the taxonomical characters proposed by Tchudinova (1980): microstructure, septal spines, juna sections and has a early-middle Brigantian distribution (Fig. 6A-B).
Multithecopora sp.C shows a more bushy growth than the previous morphotypes, forms better developed colonies, and the corallites present less septal spines (Fig. 6C-D).This morphotype occurs in the early Brigantian from El Collado (zone 16 of Mamet, 1974).Multithecopora sp.A, B and C occur only in the Viséan.
Multithecopora sp.H shows a phaceloid growth habit and encrusting on rugose corals.Their characteristics are common in Multithecopora genera: the diameter/lumen rate and the dimensions, the presence of septal spines, and a colonial development forming small bushy colonies (Fig. 6E-F).This morphotype is known only from the Serpukhovian (Pendleian Stage, Table 2).
Another significant genus in the Viséan recorded from the Ossa-Morena Zone is Syringopora.Two morphotypes have been recognized: Syringopora sp.A and Syringopora sp.B. Both morphotypes show the main characteristics of Syringopora.The differences between them are that Syringopora sp.B is larger than Syringopora sp.A, and has a higher lumen diameter.Syringopora sp.B shows a fasciculate development, with less density of corallites and branched colonies (Fig. 7A-D).Syringopora sp.A shows a palisade development with a high density of corallites (Fig. 7E-F).The morphology of the corallites of Syringopora sp.A is more irregular than that of the morphotype B, which present a more cylindrical development.Syringopora sp.A occurs only in the Los Santos de Maimona Basin and in Los Santos and Cerro Almeña sections of late Viséan (middle-late Asbian) age.Whereas Syringopora sp.B occurs in the Guadiato Area, and more specifically in the Antolín and La Adelfilla sections and is of late Viséan (early Brigantian) age.Syringoalcyon is another common genus in Ossa-Morena.It has been recorded in the Los Santos de Maimona and Cerro Almeña sections with a distribution of Asbian-Brigantian.This genus presents distinctive epithecal scales and shows characteristics very similar to Syringopora (Fig. 7G-I).For this reason some authors such as Hill (1981) and Tourneur et al. (1995) identified it with Syringopora.Its distribution is middle Asbian.The epithecal scales of the samples of Los Santos de Maimona Coal Basin do not show a dense packing and are thinner than those described in the literature.
Roemeripora sp.occurs only in the Fuenteobejuna section as massive cerioid colonies, where the corallites show a dense packing with prismatic and irregular forms, with abundant septal spines and connecting tubuli (Fig. 8E-F).It occurs from late Asbian to early Brigantian (Cózar et al., 2007).
Cladochonus sp.A is one of the two morphotypes (A and B) that occurs in the Iberian Peninsula.It shows an initial tubular development with a secondary globular enlargement and "diaphragms" between corallites as well as the lack of tabulae and spines (Fig. 9C-D).This morphotype occurs in the lower levels of the El Collado section, which is uppermost Asbian in age (Zone 15 of Mamet, 1974 biostratigraphy).
Four morphotypes and one nominal species of Multithecopora have been recognized in the Cantabrian Zone: Multi- corallites show circular to prismatic sections, sometimes sharing the wall with neighbouring corallites (Fig. 8A-D).This taxon shows a thick wall with abundant septal spines and frequently connecting tubuli.The tabulae are variable in shape (curved, horizontal or infundibuliform).This genus is similar to Multithecopora in the structure of the wall.It shows alternating fibrous and lamellar layers with higher development of the lamellar layers.This species occurs in two sections, in the Playa de la Huelga, where it occurs associated with chaetetids and rugose corals and in the Prioro section, where it appears associated with chaetetids and Multithecopora sp.G and has an late Moscovian (Podolskian-Myachkovian) age.Sinopora also occurs in the Celada de Roblecedo section and shows a bushy colonial morphology with cylindrical corallites similar to Multithecopora, but with deeper calices and absent septal spines.The tabulae are rare (scarce or absent) and concave (Fig. 11E-F).The age of this morphotype is late Moscovian (Myachkovian).
Cladochonus sp.B occurs in the Valdeteja section.This morphotype presents the classical features of this genus, as compiled by Hill (1981) and later Stasinska (1982): coral prostrate, which in distal parts presents erect branches that seem forked, with a characteristic growth in zigzag, inner "diaphragms" between corallites as well as the lack of the septal apparatus, and scarce curved tabulae (Fig. 9A-B).The level of Cladochonus is early Bashkirian in age (Akavasian horizon, Villa et al., 2001).
Aulopora sp.A shows a thick wall similar to Multithecoporidae, but it does not show septal spines and the microstructure is poorly preserved.However, a fibrous domain and an inner and thicker homogeneous lamellar domain are distinguished (Fig. 13A-B).The tabulae are curved (concave and convex) and frequent.
Aulopora sp.B shows a more open calyx lumen and thinner wall than Aulopora sp. A. Septal spines are absent and tabulae are infundibuliform as in Syringopora.The microstructure is composed of an outer fibrous layer more developed than that in Aulopora sp.A (Fig. 13C-F).
Two colonies of Mastopora?sp.show reptant and densely packed colonies, which form continuous encrusting sheets.Occasionally, it may form a globular shape, when the successive sheets are joined.Although the collected samples do not display the typical mammilliform shape of Mastopora corallites, the growth habit and the presence of sheet-like structures point to this genus.Two colonies have been sampled in the Playa de la Huelga section.The calices are raised and present a small aperture and thick walls, but the relation-thecopora sp.D, Multithecopora sp.E, Multithecopora sp.F, Multithecopora sp.G, and Multithecopora hontoriense Rodríguez and Ramírez, 1987.Multithecopora sp.D shows phaceloid colonies composed of small corallites that show septal projections and have a well-developed inner fibrous domain or an alternation of fibrous and lamellar domains.The growth pattern is prostrate in early stages, but later the corallites develop an erect growth, with subsequent budding in some cases (Fig. 10A-B).This morphotype occurs in the Valdeteja section at higher levels than the "Cladochonus band" of Winkler Prins (1971), which could occur from early Bashkirian? to early Moscovian rocks (Villa et al., 2001), but it is more probable that it occurs in a middle Bashkirian to early Moscovian (Tashatinian -Vereian) horizon.
Multithecopora sp.E shows diameter and septal projections similar to the previous morphotype but presents some differences, such as the microstructure (only three domains, mainly lamellar), and the growth habit (phaceloid and bushy).This morphotype grows encrusting other organisms, such as rugose corals or Chaetetes.The corallite length is very short, showing an open calyx almost from the beginning of the offsetting (Fig. 10C-F).This morphotype occurs in two sections in the Cantabrian Zone; in the Las Ilces section, middle Bashkirian in age (Tashatinian horizon, Coronado, 2008) and in the Piedrasluengas section, early Moscovian in age (Vereian horizon, van der Graaff, 1971a).
Multithecopora sp.F is similar to the previous morphotype; the differences are in the growth habit; this morphotype is reptant or rarely bushy, shows a smaller diameter and smaller septal protrusions (Fig. 11A-B).This morphotype only occurs in the Este de Camasobres section that is late Moscovian in age (Kashirian horizon, van der Graaff (1971b), Westphalian C sensu Boll, 1985).
Multithecopora sp.G shows a bushy development of the colonies and a smaller diameter than previous morphotypes.This morphotype presents scarce septal spines that are small and short (Fig. 11C-D).The colonies are composed of many corallites and grew encrusting on chaetetids and other bioclasts.This morphotype only occurs in the Prioro section that is late Moscovian in age (Podolskian -early Myachkovian).
Multithecopora hontoriense presents a larger diameter than other Multithecopora of the Cantabrian Zone; they built erect, densely packed or branching, bushy colonies (Fig. 12A-H).The corallites show scarce septal spines but frequent septal projections that offer an undulating microstructure.This morphotype presents fibrous inner and outer layers and, sometimes, a thin fibrous middle layer.It is present in two sections of the late Moscovian.It occurs in the Pico Guillermo section that is Kashirian-Podolskian in age and in the Playa de la Huelga section that is Podolskian-Myachkovian in age.
The taxon Neomultithecopora cantabrica shows phaceloid to submassive colonies with lateral increase.The     alternate with storm beds where corals and brachiopods are reworked.Auloporids occur in growth position at the top of some beds developed in a shallow-water platform (above the wave-base) from Cerro Almeña.Fragments of the same corals occur in the middle part of the beds.Auloporoids occur in more diverse environments, with Multithecoporidae the dominant auloporids in the Viséan from the Guadiato Basin.They lived at the top of microbial mounds (Sierra de la Estrella Section, Rodríguez-Martinez et al., 2003), in patch reefs (Antolín Section, Rodríguez and Rodríguez-Curt, 2002), and in shallow-water platforms affected by storms (El Collado Section; Fuenteobejuna Section, Cózar et al., 2007;and Adelfilla Section).In all cases they are associated with diverse assemblages that include rugose corals, chaetetids, brachiopods, crinoids, bryozoans, algae, cyanobacteria and foraminifers.
The Serpukhovian rocks from the Guadiato Basin yielded a poor assemblage of auloporoids (San Antonio and La Cornuda sections, Gómez-Herguedas and Rodríguez, 2008) that lived in small mud mounds mainly composed of algae, rugose corals, chaetetids and peloidal wackestone produced by microbial communities.
During the Pennsylvanian there is a change in the benthic communities, but the Multithecoporidae were still present and became dominant components in many environments.Consequently, they occur in many Pennsylvanian localities from the Cantabrian Zone.
Auloporids occur in the Bashkirian and Moscovian, being a main or a secondary component of reef mounds built by them, associated with calcareous algae (Donezella, Anthracoporella and/or phylloid algae), as well as rugose corals, chaetetids and microbial communities (Las Ilces Section, Coronado and Rodríguez, 2009;Prioro section, van Loon, 1971; Celada de Roblecedo and Pico Guillermo sections (van der Graaff, 1971b).As in the Mississippian, they also occur at the top of microbial and algal mounds and in surrounding facies (Valdeteja Section, Eichmüller, 1985).Auloporoids are also common in shallow-water platforms.They built biostromes associated with rugose corals and chaetetids (Piedras Luengas Section, Minwegen, 2001) and built reefal structures associated also with rugose corals and chaetetids (Playa de la Huelga Section, Minwegen 2001;Bahamonde, 2008).Occasionally, they occur in shallow-water platforms with soft bottom, growing on rugose corals or brachiopods (Playa de la Huelga, Rodríguez and Ramírez, 1987;Ribadesella, Rodríguez et al., 1997 and Este de Camasobres sections).
Most of the Auloporida that are found in these environments belong to the superfamily Syringoporicae, which show phaceloid and more rarely cerioid morphology, with a diverse density of occurrence and growth-directions of corallites.The growth strategies of tabulate corals were analyzed by Scrutton (1997).They depend on the strength of substrate, the competitiveness with other organisms and the environmental conditions during the colony development.The Syringoporicae of the Iberian Peninsula show diverse strategies: ship (diameter/lumen) is low, because the lumen is usually open (Fig. 9E-F).This morphotype shows scarce, small septal spines, and acute shape and thick concave tabulae.These morphologic criteria suggest that this morphotype belongs to Mastopora.The genus Mastopora has been found previously only in the Silurian and Devonian, but as the section Playa de la Huelga has been dated as upper Moscovian (Podolskian) we use this genus with question mark.

Microfacies and palaeoecological characteristics
The sections sampled offer a large variety of environments, microfacies, and associations where the Carboniferous auloporids from the Iberian Peninsula could grow.Table 2 shows a compendium of data of the different microfacies found in studied samples (section, microfacies, geometry and lithology of the beds, components, depositional environment and characteristics derived from the study of the other components, fabrics, morphotypes, and age).
These data show that the dominant microfacies are coral or chaetetid boundstone (sensu Dunham, 1962).The bioclastic microfacies (e.g.bioclastic wackestone, packstone or grainstone) are common too, and they formed in a large variety of environments (flanks of buildups, shallow tidal flats or storm beds in inner or medial carbonate platforms).
The predominant host rock in these sections is massive limestone, occasionally with domical shape.Marls and silty limestones are subordinate in some sections.The most common occurrence of auloporoids is in the core of reef mounds, patch-reef and reef systems.Auloporids also occur in the capping beds of microbial mounds.The bedded limestones instead, are associated with bioclastic microfacies dependent on energetic environments, such as talus facies or storm beds.
The fossil assemblages related to the Auloporida in the Iberian Peninsula are dominated by the presence of crinoids, calcareous algae, chaetetids and other corals.It suggests that those communities are developed in shallow to moderately deep seas that present well-oxygenated and marine normal salinities.

Results and Discussion
The Carboniferous Auloporida from the Iberian Peninsula occurs in a large variety of environments and they were related to a wide spectrum of other invertebrate groups (Table 2).
The oldest occurrences are recorded in the upper Viséan (Middle Mississippian) in the Los Santos de Maimona and Cerro Almeña sections.Auloporids occur there in two different environments: reef flat and shallow-water platform.The Auloporids related to reef-flat platforms (Rodríguez et al., 1992;Rodríguez, 1996) show a diverse assemblage dominated by gigantoproductid brachiopods that are the base for the attachment of rugose corals and auloporids (Syringoporidae are the dominant auloporids).Well-preserved build-up beds   Syringopora and Syringoalcyon in Los Santos de Maimona and Cerro Almeña Sections show phaceloid (palisade) colonies with the main development in the periphery (Fig. 7 E-I).This strategy is possible because of the presence of hard substrate such as brachiopod shells or rugose corals and protection against high energy of the waves.The vertical growth is unlimited in Cerro Almeña, but limited by the level of low tides in Los Santos de Maimona.
Multithecopora hontoriense from Playa de la Huelga and Pico Guillermo sections shows a similar strategy (Fig. 12. A-B, F).In this case, the corallites are closely packed and show connecting tubuli.These colonies grew on chaetetid colonies.Roemeripora from Fuenteobejuna Section (Fig. 8. E-F) and Neomultithecopora cantabrica from Playa de la Huelga section share the same strategy and develop massive colonies (Fig. 8. C-D).Multithecopora sp.D (Valdeteja section), Multithecopora sp.B (Fuenteobejuna section), Multithecopora sp.F (Este de Camasobres section), Neomultithecopora cantabrica (Prioro and Playa de la Huelga sections) and some specimens of Multithecopora sp.A (Sierra de la Estrella) show an initial stage of reptant growth 7. B;Fig. 11. B) followed by an erect growth with corallites vertical and parallel forming typical phaceloid colonies (Fig. 10A-B).
Multithecopora sp.E (Las Ilces and Piedrasluengas sections), Sinopora (Celada de Roblecedo Section), Multithecopora sp.G (Prioro Section), some colonies of Multithecopora sp.F (Este de Camasobres Section) and Sinopora (Celada de Roblecedo Section) follow the strategy of developing a stepped offsetting in response to an aggrading substrate (when they grew related to microbial communities) or to competition with other organisms.Well-preserved examples of this strategy are found also in Multithecopora hontoriense (Pico Guillermo section) and Multithecopora sp.E (Las Ilces section), where the colonies are influenced by the substrate that cut the vertical development and finally is distorted in several bands (Fig. 10.D; Fig. 12. C).
The Auloporicae that do not occur in buildups and show also diverse growth strategies, adapted usually to environments with high energy or high terrigenous influx: Mastopora?occurs in calcareous sandstones with planar lamination associated with encrusting bryozoans and crinoidal ossicles.It grew in an environment of quite high energy and near shore.It shows reptant growth developing a complete encrusting sheet (Fig. 9F).
Cladochonus morphotypes show simple lateral branches with a reptant growth habit and zig-zag trajectories (Fig. 8B).Scrutton (1997) regarded this strategy as due to development in a soft substrate.
As explained above, the auloporids from the Iberian Peninsula occur in different habitats, developed diverse strategies and were related to different fossil assemblages.However, there is a typical assemblage, which is repeated in many cases.It is the "Chaetetid-auloporoid-rugose coral buildups" described by West (1988), Minwegen (2001) and Wahlman (2002), as an interrelationship between corals and chaetetids, using each other as substrate and framework.The Pennsylvanian buildups from the Iberian Peninsula show different assemblages of reef-building organisms, including Donezella, Anthracoporella, Petschoria, phylloid algae and bryozoans.Auloporoids are present in all of them, but their most common association includes the presence of chaetetids.
Figure 14 shows the stratigraphical distribution of the morphotypes and species of auloporoid corals studied herein.The auloporoids show many overlaps between the ranges of the morphotypes in both regions (Ossa-Morena and Cantabrian zones).There is also a reduced representation in the uppermost Mississippian and lowermost Pennsylvanian.In contrast, the record is quite complete in the Viséan and from the Bashkirian to Moscovian.It is due to the scarcity of outcrops and/or the unfavourable environments.As the identification and assignation of new species names is still not completely finished, this is a provisional chart, which will be improved with further studies.

Conclusions
Auloporid corals are highly diverse in the Carboniferous of the Iberian Peninsula, mainly in the outcrops of the Ossa-Morena Zone (Mississippian age) and Cantabrian Zone (Pennsylvanian age).The auloporids have been identified following the criteria proposed by Tchudinova in (1980) with some modifications.They have been subdivided into morphotypes and grouped according to common characteristics.
Syringopora, in the Carboniferous from the Iberian Peninsula is only present in the Mississippian.The dominant genus through the Carboniferous is Multithecopora, represented by 8 morphotypes and one species.Forms with pseudocerioid growth habit were derived from phaceloid forms: Roemeripora from Syringopora in the Mississippian and Neomultithecopora from Multithecopora in the Pennsylvanian.
The genus Syringoalcyon, which is globally very scarce, is quite abundant in the Los Santos de Maimona Basin.The validity of this genus is doubtful and it will be further studied in the future.
These corals inhabited different environments, and show diverse growth strategies.They lived in buildups (reefmounds, patch-reefs), on microbial mounds, in reef-flats and carbonate shallow platforms).The microfacies study shows that these corals inhabited shallow, well oxygenated waters with normal marine salinity.Those environments allowed the development of diverse communities in which the auloporoids were related to rugose corals, chaetetids, crinoids, brachiopods, algae, foraminifers, molluscs, etc.The biostratigraphic distribution has been established for the proposed morphotypes as a provisional chart, which will be improved with further taxonomic studies.study has been supported through the Spanish Science Ministry (Project CGL 2009-1034/BTE) and the UCM Research Group 910231.Ismael Coronado acknowledges financial support through an UCM FPI grant.The authors are grateful to Isabel Díaz Megías for her help in the preparation of thin sections.This article is a contribution to the Spanish Working Group IGCP 56.

Fig. 5 .
Fig. 5.-Multithecopora sp. A. A) Fragments of corallites in storm beds from El Collado Section.B-C) Branched corallites from Antolín section on thrombolitic-microbial texture.Note the growth of automicrite around the corals and the pseudostromatactoid cavities in B. D-F) Sierra de la Estrella section.D) Encrusting habit of Multithecopora sp.A on a rugosan.E-F) Phaceloid development, parallel with an initial reptant growth.G) Multithecopora sp.A in Los Santos de Maimona section growing in a reef-flat facies.Note the dolomite development around the corallites.H) Reworked facies in Los Santos de Maimona section.Note the fragmentation and abrasion of the corallites.I) Multithecopora sp.A in shallow-water facies from Fuenteobejuna section.Note the brecciation and the reworked corallites.Scale bar is 2 mm.

Fig. 7 .
Fig. 7.-A-B) Syringopora sp.B from La Aldelfilla section in a matrix with cortoids and peloids.C-D) Branched development of Syringopora sp.B from Antolín section in microbial texture.E-F) Syringopora sp.A from Los Santos de Maimona section.Note the palisade development of the colony.G-I) Syringoalcyon sp.G) Detail of the epithecal scales on the corallites of Cerro Almeña section.Note the sparite cement between the corallites in reef-flat facies.H-I) Syringoalcyon sp. from Los Santos de Maimona section.Note the dense packing of the epithecal scales around the corallites in I and the growth in palisade of this morphotype in H. Scale bar is 2 mm.

Fig. 8 .
Fig. 8.-A-D) Neomultithecopora cantabrica Rodríguez and Ramírez, 1987.A-B) Samples from Prioro section.Note the massive-proximal and prismatic habit of the corallites in A. B) Reptant initial development of the colony and the vertical growth later.C-D) Samples from Playa de la Huelga section.C) Note the massive development of the colony that initially is encrusting a chaetetid.D) Phaceloid habit with connecting tubuli between corallites.E-F) Roemeripora sp. from Fuenteobejuna section.Note the massive and prismatic development of the corallites and the communication between them through connecting tubuli.Scale bar is 2 mm.

Fig. 9 .
Fig. 9.-A-B) Cladochonus sp.B from Valdeteja section.A) Caldochonus wackestone with many corallites oriented in the bottom of the strata.B) Detail of zigzag development of three-dimensional sample on the bedding plane.C-D) Cladochonus sp.A from El Collado section.C) Note the diaphragm in the inner part of the calyx.D) Detail of Cladochonus encrusting a rugose coral in a storm bed.E-F) Mastopora?Detail of the colony in thin section.Note the septal spines and the open calices.F) Colony in the calcareous sandstone encrusting and being encrusted by bryozoans.Scale bar is 2 mm.

Fig. 10
Fig. 10.-A-B) Multithecopora sp.D from Valdeteja-Las Majadas sections.Note the vertical and parallel development of the colony in a typical microbial matrix with pseudostromatactoid cavities, peloids and micritic envelope.C-F) Multithecopora sp.E. C-D) Samples from Las Ilces section.Note the encrusting habit on a rugosan from C in a microbial facies.D) Strategy of developing a stepped offsetting in response to an aggrading substrate in a Donezella core mound.E-F) Samples from Piedrasluengas section.E) Note the encrusting habit on a chaetetid in a microbial texture from the bioherm facies.F) Detail of the phaceloid to bushy habit of the colony.Scale bar is 2 mm.

Fig. 11
Fig. 11.-A-B) Multithecopora sp.F from Este de Camasobres section.A) Detail of the reworked facies where the corallites show fragmentation and abrasion.B) Reptant growth of the corallites in microbial matrix.C-D) Multithecopora sp.G from Prioro section.Growth of the colonies in a microbial substrate and presence of open calices with thicker walls.E-F) Sinopora sp. from Celada de Roblecedo section.E) Prostrate and tumbled corallites growing in steps.F) Reworked facies of Sinopora with abundant phylloid algae.Scale bar is 2 mm.

Fig. 12
Fig. 12.-Multithecopora hontoriense Rodríguez and Ramírez, 1987.A-C) Samples from Pico Guillermo section.Note the phaceloid habit and dense packing of corallites producing a massive colony.C) Stepped offsetting developed in response to an aggrading substrate with vertical corallites in the top and tumbled or prostrate ones in the bottom of the colony.D-F) Samples from Playa de la Huelga section.Note the vertical and parallel development of the colony in D and F. E shows a branched development with a short growth of the corallites.Scale bar is 2 mm.

Fig. 13
Fig. 13.-A-B) Aulopora sp.A from Ribadesella section.A) Detail in thin section of this morphotype.Note the thin infundibuliform tabulae and the incrustation on a rugose coral.B) Note the reptant habit of the corallites growing on a rugosan.C-F) Aulopora sp.B from Ribadesella section.C) Detail of the branching bushy habit of a colony.D) Detail in thin section from the corallites; note the differences with Aulopora sp. A. E) Encrustation of a chaetetid on a rugosan and Aulopora on and between the chaetetid.F) Reptant growth on a rugose coral.Scale bar is 2 mm.

Fig. 14
Fig. 14.-Biostratigraphical distribution of the auloporid corals found in the Iberian Peninsula.Note the gap between the upper part of the Mississippian and the lower part of the Pennsylvanian.

Table 2 .
-Localities and microfacies associated with the auloporid corals, geometry and lithology, main components, depositional environment and characteristics, morphotypes and age.