{'fraction_non_alphanumeric': 0.029112509557136977, 'fraction_numerical': 0.017585132035523143, 'mean_word_length': 5.131987017670393, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 1, 'xml': 0}, 'pii_count': 1, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Early Aptian corals from Peñascal (Bilbao, N Spain)

From two horizons in the lower Aptian Peñascal limestone Formation south of Bilbao 22 coral species are reported. The corals belong to the scleractinian families Actinastraeidae, Eugyridae, Haplaraeidae, Latomeandridae, and Solenocoeniidae, and the octocorallian family Helioporidae. The stratigraphic distribution of the species lies between the Berriasian to Cenomanian, but most species have a distribution between the Barremian and Albian. The faunas show most palaeobiogeographical relationship to faunas from the Hauterivian to Albian of the European Boreal, the Western Atlantic and the Western Tethys.


INTRODUCTION
Although the early Aptian is one of the periods with the most abundant co-existing coral genera and species in the Cretaceous (Löser, 2016), little data is reported from northern Spain. There are some reports from Aragón (mainly around Teruel) and from Cataluña (Ulldecona; Löser et al., 2005). From the Basque country, material is only reported from the Peñacerrada diapir (Sachs, 2002).
Here, another two stratigraphic intervals containing coral faunas in the vicinity of Bilbao are described.

Geological setting
The investigation was carried out in the Peñascal quarry ( Fig. 1). This lies in the southern outskirts of Bilbao city, just SW of the Supersur highway. The Peñascal quarry lies in the Basque-Cantabrian Basin, and belongs to the Basque Arch, the western prolongation of the north Pyrenean Zone, encompassing the Basque Paleozoic Massifs and their westerly adjunct Mesozoic and Cenozoic sedimentary cover (Rat, 1959). More precisely, the quarry lies in the northern margin of the Bilbao Anticlinorium, with a NW-SE running axis-trend. The quarry outcrops occur south of Arnotegi fault. Several faults of this Arnotegi system reveal synsedimentary activity and were responsible for the diversity and partitioning of sedimentary settings during the Aptian. Deposition occurred as the result of extensional rifting movements related to the opening of the Bay of Biscay (Boillot, 1984;Olivet, 1996;Le Pichon, et al., 1971;Sibuet, et al., 2004;García-Mondejar, et al., 2018). Later in the Alpine-Pyrenean orogeny, those units were folded and fractured to its present situation and structure following compressive movements at the boundary of the Iberian and European tectonic plates.

Stratigraphy and sedimentology
Two coral horizons have been investigated. They stand respectively at the base and upper part of the Peñascal limestones. Biostratigraphic data indicate that the corals belong to the Dufrenoyia furcata Zone of the early Aptian, based on orbitolinid and ammonite correlation (Fernández-Mendiola et al., 2017).
The first horizon is located from metre 12 to 15 of the Peñascal quarry section (Fig. 2). Corals occur within a 3 metre-thick unit of wavy, slightly argillaceous limestone that forms the base of the Peñascal Formation. This unit is transitional between the underlying marlstones of the Ereza Formation and the overlying micritic limestones of the Peñascal Formation. The underlying marls contain echinoderms, local burrow structures and scattered plants debris. They have been interpreted as estuarine siliciclastic deposits (García-Garmilla, 1987;Fernández-Mendiola et al., 2017). The marls gradually evolve to marly limestones and wavy limestones. The latter are fine-grained packstones to wackestones with corals. The succession records a marine transgresion from coastal environments to a mixed carbonate-siliciclastic marine shelf. Corals growth forms are massive and colonies reach sizes up to 20 centimetres. The coral facies are replaced upward by micritic limestones with requieniid rudists. This vertical evolution reveals a shallowing upward trend and the rudist-dominated carbonate muddy environment reflects siliciclastic-free restricted settings.
The second horizon occurs from metre 140 to 163 of the section (Fig. 2). The succession is divided into three sub-units. Sub-unit 1 (metres 15 to 40) consists of requieniid limestones with occasional miliolid foraminifera and several packages of wavy limestones with marly partings. Two paleokarst horizons occur at metres 20 and 38 respectively suggesting periods of subaerial exposure of the carbonate platform. The sub-unit is interpreted as an inner carbonate platform with occasional phases of turbid water responsible for the argillaceous sedimentary imprint. Sub-unit 1 shows absence of coral facies.
The second sub-unit spans from metre 40 to 110. It consists of limestones dominated by requieniids punctuated with several horizons of scattered massive and/or ramose corals (Latohelia) that occur together with rudists. In this second sub-unit, three paleokarst horizons are recognised at metres 57, 80 and 89. These facies associations of rudists and corals reveal more open-water conditions in the shallow-water carbonate platform with respect to sub-unit 1.
The third sub-unit spans from metre 110 to 163, and consists of alternating massive and wavy limestone intervals. Corals in this sub-unit are overall more abundant than rudists except for the beds spanning from 116 to 120 m, which are requieniid-dominant. At metre 145 rudists recover and coexist with corals. Except for those two intervals, coral dominance suggests more open-water conditions than sub-unit 2. The succession indicates a transgressive trend from base to top of the Peñascal limestone.
We have sampled the upper part of the Peñascal limestones from metre 140 to 163, coral horizon-2 in Figure 2, for thin section and taxonomic analyses. Massive coral-head type forms alternate vertically with ramose corals, both in massive micritic limestones and in wavy argillaceous marly-micritic limestones. The marls tend to occur in isolated partings less than one centimetre-thick, and correspond to periods of increased turbid waters on the sea-floor. From metre 163 up the drowning of the carbonate platform is marked by the end of the Peñascal limestones and the encroachment of the overlying Bilbao marlstones. Those marlstones were sedimented in outer slope environments dominated by settling of silts and muds and inhabited by oysters, bivalves, echinoderms and ammonites.

MATERIAL AND METHODS
About 30 corals were collected from horizon 1 and about 50 from horizon 2. Finally six specimens from horizon 1 and 31 specimens from horizon 2 could be assigned to a species. The corals from horizon 1 are strongly recrystallized and therefore poorly preserved. Corals from horizon 2 are partly better preserved. Coral specimens were cut and polished. Thin sections in both transversal and longitudinal orientation were prepared where possible. Thin sections were scanned by passing light through them using a flatbed scanner with an optical resolution of 6,400 dpi. Scanned images were then transferred to grey scale bit maps. Their quality was amended by histogram contrast manipulation (contrast stretching) where possible. Corallite dimensions were systematically measured using the PaleoTax/Measure (http://www.paleotax.de/ measure). For each type of measurement (calicular diameter and distance, width and distance of calicular row), in one thin section, the following values were obtained: n: number of measurements min-max: lowest and highest measured values µ: arithmetic mean (average) s: standard deviation v: coefficient of variation according to K Pearson µ ± s: first interval The obtained values were compared against those for specimens in worldwide fossil coral collections, and an associated image database (ca. 26,900 specimens, ca. 15,200 illustrated, located in the Estación Regional de Noroeste (ERNO), Sonora, Mexico). Data storage and processing were carried out using the PaleoTax database program (Löser, 2004).
The material is kept at the Museo de Ciencias Naturales de Álava. Since final collection numbers are not provided before publication, here the field numbers are given. These numbers are also valid for the thin sections.

SYSTEMATIC DESCRIPTION
The preliminary classification system introduced in Löser (2016) is used here. This system does not apply suborders, but superfamilies that group families together. Contrary to the former classification system based on suborders, superfamilies may constitute monophyletic groups. The basic characteristic for the distinction of superfamilies is the relative size of the trabeculae (in the ratio of the trabeculae to the septa). Further distinction is made based on the presence or absence of synapticulae and the septal perforation. Detailed description of superfamilies, families and genera are given in Löser (2016) and are not repeated here. Since the species within a genus are entirely distinguished on the basis of morphometric data (dimensions of the corallite, number and/or density of septa), descriptions of species are not given.
The distribution data are almost entirely based on wellexamined material. Material only mentioned in the literature and material not available or insufficiently described and illustrated in the literature was not taken into account. To obtain better insight into the distribution patterns of the coral fauna of the Peñascal area, much unpublished material was included.
The abbreviations used in the synonymy lists follow Matthews (1973): *: Earliest valid publication of the species name.
?: The assignation of this description to the species is doubtful (so marked quotations are not reflected in the stratigraphic and palaeobiogeographic distribution).
p: The described material belongs only in part to the species concerned.
v: the specimen was observed by the first author.

Stelidioseris icaunensis
Other occurrence: Hauterivian of the European Boreal (France), Aptian to early Albian of the Central Tethys (Greece, Romania), Western Tethys (Spain), and the Western Atlantic (Mexico, USA).
Other occurrences: Hauterivian to early Cenomanian of the European Boreal (France, Germany) and the Western Tethys (Spain).
Genus Latohelia Löser, 1987 Latohelia is a phaceloid coral with a small corallite diameter. It was recently (Löser, 2014(Löser, , 2016 illustrated and described. Formerly, Lower Cretaceous corals of this type were assigned to the genus Calamophylliopsis. This genus differs greatly from Latohelia in having a much larger corallite diameter, compact septa that are fused in the centre of the corallite and very irregular pennulae (Löser, 2016, 219) and very probably does not occur in the Cretaceous.

Synonymy
Other Occurrence: The species is only known from the early Aptian of the type locality (Bilbao, Mina Abandonada) and the study area. The type locality probably refers to an iron mine within the limestones of the same Peñascal Formation that lies below the city of Bilbao.
Genus Thalamocaeniopsis Alloiteau, 1954 The genus was described and illustrated in Löser (2016). It is well defined but rarely recognised in the literature because its first description and illustration were poor. The genus shows a cerioid corallite arrangement and has polygonal corallites. The septa are perforated at the inner margin only, they bear pennulae and their symmetry is irregular. The genus is not rare; about 15 species reaching from the middle Jurassic to the Cenomanian are known.
Genus Eugyra Fromentel, 1857 The genus was described and illustrated with the type and topotypical material in Löser (2016 Occurrence: Early Aptian, Furcata Zone of Spain (País Vasco, Vizcaya) Bilbao, Peñascal, 1.5 m below top of the formation, in the cutting of the quarry (140325).
Other occurrences: Worldwide from the Hauterivian to Lower Albian.
Cryptocoenia annae (Volz, 1903 Remarks: Under this species, material is collected that belongs to Cryptocoenia or a related genus, but without any septa. Their absence can be also due to poor conservation. The three samples possess differing corallite dimensions. Genus Holocystis Lonsdale, 1849 The genus was revised in Löser (2006). Volz, 1903 ( Remarks: The material shows slightly larger corallite dimensions compared to the holotype of the species. As in the type, only 8 to 11 septa are developed, but up to 16 are visible, partly only as costae.
Other occurrences: Late Barremian to Aptian of the Western Atlantic (Mexico) and the Tethys (Greece, Spain, Tanzania).
Other occurrences: Aptian of the Western Atlantic (Mexico).
Superfamily Misistelloidea Eliášová, 1976 Plesiosmilia Group The genus Plesiosmilia was long-time assigned to the Axosmiliidae family. It cannot remain in this family because Axosmilia is poorly defined. The so-called lectotype of its type species (Caryophyllia extinctorium Michelin, 1841; MNHN M00053, figured specimen, figured again in Löser, 2016) is an unsectioned, poorly preserved solitary coral. The type status of the so-called paralectotypes (MNHN M00050) is uncertain. The type of the type species of Plesiosmilia (Plesiosmilia turbinata Milaschewitsch, 1876; MB K3500) is well preserved but because it is silicified, remains without a trace of microstructures. In a certain way comparable material from the Cretaceous shows septa made of small trabeculae resulting in a median dark line, with occasionally horizontally branching trabeculae form pronounced granules at the surface of the septa that are not aligned. The Plesiosmilia group is further characterised by a regular septal symmetry, compact thick septa, the absence of a wall (but presence of an epitheca), a well-developed endotheca and occasionally columella. The group collects solitary and phaceloid coral genera. The informal group needs a formal name that is based on material with wellpreserved fine skeletal structures.

DISCUSSION
The first horizon just on the base of the Peñascal Formation yielded only four species of the family Solenocoeniidae. One of the genera, Cryptocoenia, is a very common Middle Jurassic to Cenomanian coral genus and occurs almost everywhere. The other genus, Holocystis, is more rare. The second horizon yielded 19 species. Both horizons share only one species, Holocystis nomikosi. Latohelia ruizi is not restricted to the second horizon but occurs in the whole upper part of the Peñascal Formation.
The difference between horizons must be found in the ecological conditions that were better for corals towards the upper part of the formation. The early Aptian was very rich in species and genera on a global scale. When only considering the 2550 Cretaceous localities from which corals are reported in the literature, with descriptions and illustrations, about 140 coral localities have a early Aptian age (5.5%), and, when including a slightly longer time period 375 localities with corals have a range from the late Barremian to the Aptian (15%). This is also reflected in the distribution of the species found in the Peñascal Formation (Fig. 9). Most were already known from the early Aptian. Roniewicz, 1968(Löser, 2008. Latohelia was established in recent times and only up to now it was found that it should be applied to material that formerly was assigned to Calamophylliopsis. Finally Thalamocaeniopsis did not receive much attention because the original description and illustration of the taxon was so poor that it was neglected by coral workers. This means that the latter three genera are probably more common than calculated by Löser (2016) based on literature data. The palaeobiogeographical analysis does not show clear patterns due to the low number of species found in Peñascal (Fig. 10). Most correlations can be found into Hauterivian faunas of the Paris Basin, the Aptian and Albian of the Bisbee Basin (Northern Mexico) and east Iberia, the nearby northern Pyrenees and the Basque-Cantanbrian Basin.
No co-occurring species were found with the areas Aragón and from Cataluña, except for those mentioned in the synonymy lists. No co-occurring species were found with the Peñacerrada diapir (Sachs, 2002). The thickness of the bars indicates the number of localities in which the concerned species was found. The vertical grey bar indicates the age of the study deposits. Species outside of this bar have not been detected before in sediments of this age.
Compared to other early Aptian coral faunas, the Peñascal fauna is poor in species. When comparing the genera found in the study area to the published frequency of Hauterivian-Albian coral genera (Löser, 2016;fig. 6.3.3.4) it can be observed that the fauna is clearly dominated by very abundant to occasional genera (Table 1). The number of rare genera seems to be high but only one genus, Actinaraea, is well known by coral workers and more frequently reported. This is not the case for the other genera. Camptodocis was just recently re-activated and replaced the, so far only Late Jurassic Actinaraeopsis Figure 10. Correlation of provinces with joint species of the study area. Provinces with less than two joint species are suppressed and only provinces of an Early Cretaceous and Cenomanian age are shown. The correlation ratio coefficient was applied.