Cantabrian Mountains Research Articles

A new species of the productid brachiopod Aseptella from the Lower Carboniferous of the Cantabrian Mountains (Spain)

A new species of Aseptella, A. beetsi, is described fom Lower Carboniferous, Visean (Arundian-Holkerian) to lower Namurian (Arnsbergian) griotte limestones of the Cantabrian Mountains, variously called Alba or Genicera Formation. The new species, with a weakly developed brachia! median septum, seems to be the ancestor of the type species, A. asturica, from the Bashkirian of Cantabrian Mts, which only develops a median septum in its juvenile specimens. The new species shows a peculiar offshoot of the marginal ridge, possibly for better separation of the ears. The systematic position of the genus Aseptella is briefly discussed as are the implications of the occurrence of this genus in Argentina.

Corals from Asturian substage in Cantabrian Mountains: A review

Corals from Asturian substage in Cantabrian Mountains: A review

First record of Gzhelian fusulinaceans from the Carboniferous of northern Spain

Several fusulinacean species of Gzhelian age have been found in a section close to the village of Asiego, in the northern part of Picos de Europa Massifs (Cantabrian Mountains). These specimens, which were collected in limestone beds from the upper part of the Puentelles Formation, belong to the genera Triticites, Rauserites, Jigulites, Ferganites and Quasifusulina and are the youngest fusulinaceans recorded in the Carboniferous of the Cantabrian Mountains. Among these microfaunas, Jigulites sp. bears the main stratigraphic significance since the Jigulites species are considered to be restricted to the Gzhelian stage. Therefore, the discovery of these species proves the presence of Gzhelian marine deposits in the area.

Factors influencing the ground thermal regime in a mid-latitude glacial cirque (Hoyo Empedrado, Cantabrian Mountains, 2006–2020)

Air and near-surface ground temperatures were measured using dataloggers over 14 years (2006–2020) in 10 locations at 2262 to 2471 m.a.s.l. in a glacial cirque of the Cantabrian Mountains. These sites exhibit relevant differences in terms of substrate, solar radiation, orientation, and geomorphology. Basal temperature of snow (BTS) measurements and electrical resistivity tomography of the talus slope were also performed. The mean annual near-surface ground temperatures ranged from 5.1 °C on the sunny slope to 0.2 °C in the rock glacier furrow, while the mean annual air temperature was 2.5 °C. Snow cover was inferred from near-surface ground temperature (GST) data, estimating between 130 and 275 days per year and 0.5 to 7.1 m snow thickness. Temperature and BTS data show that the lowest part of the talus slope and the rock glacier furrow are the coldest places in this cirque, coinciding with a more persistent and thickest snow cover. The highest temperatures coincide with less snow cover, fine-grained soils, and higher solar radiation. Snow cover has a primary role in controlling GST, as the delayed appearance in autumn or delayed disappearance in spring have a cooling effect, but no correlation with mean annual near-surface ground temperatures exists. Heavy rain-over-snow events have an important influence on the GST. In the talus slope, air circulation during the snow-covered period produces a cooling effect in the lower part, especially during the summer. Significant inter-annual GST differences were observed that exhibited BTS limitations. A slight positive temperature trend was detected but without statistically significance and less prominent than nearby reference official meteorological stations, so topoclimatic conditions reduced the more global positive temperature trend. Probable existence of permafrost in the rock glacier furrow and the lowest part of the talus slope is claimed; however, future work is necessary to confirm this aspect.

Combined influence of maximum accumulation and melt rates on the duration of the seasonal snowpack over temperate mountains

The duration of the seasonal snowpack determines numerous aspects of the water cycle, ecology and the economy in cold and mountainous regions, and is a balance between the magnitude of accumulated snow and the rate of melt. The contribution of each component has not been well quantified under contrasting topography and climatological conditions although this may provide useful insights into how snow cover duration could respond to climate change. Here, we examined the contribution of the annual peak snow water equivalent (SWE) and the seasonal melt rate to define the duration of the snowpack over temperate mountains, using snow data for mountain areas with different climatological characteristics across the Iberian Peninsula. We used a daily snowpack database for the period 1980–2014 over Iberia to derive the seasonal peak SWE, melt rate and season snow cover duration. The influence of peak SWE and melt rates on seasonal snow cover duration was estimated using a stepwise linear model approach.The stepwise linear models showed high R-adjusted values (average R-adjusted = 0.7), without any clear dependence on the elevation or geographical location. In general, the peak SWE influenced the snow cover duration over all of the mountain areas analysed to a greater extent than the melt rates (89.1%, 89.2%, 81.6% 93.2% and 95.5% in the areas for the Cantabrian, Central, Iberian, Pyrenees and Sierra Nevada mountain ranges, respectively). At these colder sites, the melt season occurs mostly in the spring and tends to occur very fast. In contrast, the areas where the melt rates dominated snow cover duration were located systematically at lower elevations, due to the high interannual variability in the occurrence of annual peak SWE (in winter or early spring), yielding highly variable melt rates. However, in colder sites the melt season occurs mostly in spring and it is very fast in most of the years. The results highlight the control that the seasonal precipitation patterns, in combination with temperature, exert on the seasonal snow cover duration by influencing the peak SWE and suggest a future increased importance of melt rates as temperatures increase. Despite the high climatological variability of the Iberian mountain ranges, the results showed a consistent behaviour along the different mountain ranges, indicating that the methods and results may be transferrable to other temperate mountain areas of the world.

Allium ducissae (A. subgen. Polyprason, Amaryllidaceae) a New Species from the Central Apennines (Italy).

In this paper, Allium ducissae (the LSID for the name Allium ducissae is: 77254606-1) is described as a new species based on morphological and molecular analyses, and its taxonomic relationships are discussed. It grows in crevices on calcareous rocks, rocky slopes and grassy ledges in the subalpine belt, within two regional protected areas in the Lazio and Abruzzo administrative regions (Central Apennines, Italy). Previously, these populations were attributed to A. strictum, a species described from Siberia, belonging to A. sect. Reticulatobulbosa. The new species is distinct from A. strictum in the morphology of vegetative and reproductive structures. Indeed, it is close to A. palentinum, an endemic species to Cantabrian Mountains (NW Spain). Both molecular and morphological data support the recognition of the Allium populations coming from the Central Apennines as a new species. Allium ducissae can be clearly distinguished from A. palentinum by longer and wider tepals, longer filaments, tooth of inner filament, flower pedicels, spathe appendage, and smaller seeds. Moreover, seed testa micro-sculptures revealed slight differences between A. ducissae and A. palentinum. Chromosome counts showed that A. ducissae is diploid with 2n = 16 chromosomes, as already known for A. palentinum. Molecular analyses support the affiliation of A. ducissae and A. palentinum to A. sect. Falcatifolia, contrary to what is known for the latter species, usually included in A. sect. Daghestanica. Finally, the IUCN assessment for the newly described species is proposed and briefly discussed.

Preliminary findings on the gastrointestinal parasites of the brown bear (Ursus arctos) in the Cantabrian mountains, Spain.

No study is currently available on the parasitofauna of the population of brown bears (Ursus arctos) inhabiting the Cantabrian Mountains in Spain. The aim of the present study was to obtain novel information on diversity and prevalence of gastrointestinal parasites in these individuals. During August 2016 and from May to July 2017, 14 fecal samples were collected from the western Cantabrian bear subpopulation, in the Somiedo Natural Park, in the Spanish province of Asturias. The prevalence of parasites detected was 71% and two genera were identified: Dicrocoelium sp. and Trichuris sp. Since the impact that pathogens such as endoparasites can have on the health of bears, together with other stressors, is still poorly understood, research efforts that include disease surveillance are critical to the successful protection of this emblematic species. Our preliminary findings require further investigations, with a wider sampling effort, and bring awareness for the need of carrying further studies on this area as a part of a proactive species management plan.

The Cantabrian capercaillie: A population on the edge

The capercaillie Tetrao urogallus - the world's largest grouse- is a circumboreal forest species, which only two remaining populations in Spain: one in the Cantabrian mountains in the west and the other in the Pyrenees further east. Both have shown severe declines, especially in the Cantabrian population, which has recently been classified as “Critically Endangered”. To develop management plans, information on demographic parameters is necessary to understand and forecast population dynamics. We used spatial capture-recapture (SCR) modeling and non-invasive DNA samples to estimate the current population size in the whole Cantabrian mountain range. In addition, for the assessment of population status, we analyzed the population trajectory over the last 42 years (1978–2019) at 196 leks on the Southern slope of the range, using an integrated population model with a Dail-Madsen model at its core, combined with a multistate capture-recapture model for survival and a Poisson regression for productivity. For 2019, we estimate the size of the entire population at 191 individuals (95% BCI 165–222) for an estimated 60 (48–78) females and 131 (109–157) males. Since the 1970s, our study estimates a shrinkage of the population range by 83%. The population at the studied leks in 2019 was at about 10% of the size estimated for 1978. Apparent annual survival was estimated at 0.707 (0.677–0.735), and per-capita recruitment at 0.233 (0.207–0.262), and insufficient to maintain a stable population. We suggest work to improve the recruitment (and survival) and manage these mountain forests for capercaillie conservation. Also, in the future, management should assess the genetic viability of this population.

The origin and collapse of rock glaciers during the Bølling-Allerød interstadial: A new study case from the Cantabrian Mountains (Spain)

During the Late Pleistocene, the main mountain ranges of the Iberian Peninsula were covered by small icefields and cirque and alpine glaciers. The deglaciation triggered paraglacial processes that generated landforms, mostly within the ice-free glacial cirques. In this research we analyse the deglaciation process in the Muxivén Cirque (42°15′N – 6°16′W), in the upper Sil River Basin, which includes some of the largest relict rock glaciers of the Cantabrian Mountains. We addressed this objective by means of accurate geomorphological reconstructions, sedimentological analysis, Schmidt-hammer surface weathering measurements and a dataset of 10 10Be Cosmic-Ray Exposure ages. Results reveal that after ~16 ka, glaciers retreated to the bottom of the cirques at the headwaters of the valley, leaving the walls free of ice and triggering rock avalanches onto the remnants of these glaciers. This paraglacial process supplied debris to a small glacier within Muxivén Cirque, which transformed in two rock glaciers. These debris isolated the ice inside the rock glaciers only for a very short period of time and ended up melting completely before the Younger Dryas. The lower sector of the largest one stabilized at 14.5 ± 1.5 ka, while the upper sector remained active until 13.5 ± 0.8 ka. Previous to the stabilization of the lower sector of the northern rock glacier, at its margin a high-energy debris avalanche occurred at ~14.0 ± 0.9 ka. These data agree with previous research, corroborating the paraglacial origin of most Iberian rock glaciers during the Bølling-Allerød interstadial.

Geology of the Cabuérniga Fault System: evolution of a large Alpine structure with Variscan inheritance

ABSTRACT The Cabuérniga Fault System (CFS) extends for 150 km in E–W trend along the northern divide of the Cantabrian Mountains, near the Cantabrian Sea. This fault system was reactivated several times since the Paleozoic, and displays hydrothermal activity nowadays. We present here a detailed geological map of the whole CFS and six cross-sections distributed along strike, which allowed us to unravel the kinematic history of the individual fault segments comprising the CFS. The current CFS geometry mainly results from the reactivation of E–W Variscan thrusts and NW–SE Late-Variscan strike-slip faults during the Alpine Cycle. Reactivation took place in relation to both Permian and Mesozoic pre-orogenic extension and subsequent Cenozoic shortening. The eastern end of the CFS corresponds to a N–S structure arriving at the Cantabrian coast, while the western edge connects with the E–W trending Llanera fault, leading to an Alpine fault system extending 220 km.

New Rugosochonetidae (Brachiopoda) from the upper Bashkirian and Moscovian of the Cantabrian Mountains (N Spain).

The Rugosochonetidae are widely spread in the Carboniferous of the Cantabrian Mountains and they have often been described or cited by previous authors. In this paper we present a study of the Rugosochonetidae found in upper Bashkirian and Moscovian (Pennsylvanian) rocks from the Cantabrian Mountains. The diagnosis of the family is modified in order to accommodate forms with a typical rugosochonetid ornamentation but without a dorsal median septum, which are included in the new genus Riosanetes, type genus of the new subfamily Riosanetinae. The new species Riosanetes fernandezi (type species of the new genus), Neochonetes (Neochonetes) villamaninensis, N. (N.) saenzi, N. (N.) asturianus, and N. (N.) babianus are described. The latter species is based on material previously described by us as Neochonetes acanthophorus (Girty, 1934).

Morphological, isotopic and proteomic study of the Pleistocene and Holocene fauna of Cova dos Santos (Abadín, Lugo, NW Spain)

Cova dos Santos is a karstic cavity in Abadín (Lugo), in a hitherto unexplored area that may have been the natural route between the well-known Quaternary faunas of the Cantabrian Mountain Range and those located further south in Galicia, such as in the Serra do Courel. The surface surveys carried out during the topographic layout revealed the presence of deposits of bone remains, usually extremely fragmented, of medium and large vertebrates. Due to the nature of these remains, different molecular techniques (ZooMS, stable isotopes), radiocarbon dating, and morphological and metric analysis were used to characterise the remains present at the site. Combining these methods, it has been possible to identify different taxa such as Ursus speleaeus, Ursus arctos, Panthera pardus, Cervus elaphus, Rhinocerotidae, and to confirm the occupation of this cave since at least 43000 years ago calBP. The presence of domestic species, such as Ovis aries, Equus sp. and Gallus gallus, also shows the use of this cave in more recent times.

Transition between Variscan and Alpine cycles in the Pyrenean-Cantabrian Mountains (N Spain): Geodynamic evolution of near-equator European Permian basins

In the northern Iberian Peninsula, the Pyrenean-Cantabrian orogenic belt extends E-W for ca. 1000 km between the Atlantic Ocean and Mediterranean Sea. This orogen developed from the collision between Iberia and Eurasia, mainly in Cenozoic times. Lower-middle Permian sediments crop out in small, elongated basins traditionally considered independent from each other due to misinterpretations on incomplete lithostratigraphic data and scarce radiometric ages. Here, we integrate detailed stratigraphic, sedimentary, tectonic, paleosol and magmatic data from well-dated lithostratigraphic units. Our data reveal a similar geodynamic evolution across the Pyrenean-Cantabrian Ranges at the end of the Variscan cycle. Lower-middle Permian basins started their development under an extensional regime related to the end of the Variscan Belt collapse, which stars in late Carboniferous times in the Variscan hinterland. This orogenic collapse transitioned to Pangea breakup at the middle Permian times in the study region. Sedimentation occurred as three main tectono-sedimentary extensional phases. A first phase (Asselian-Sakmarian), which may have even started at the end of the Carboniferous (Gzhelian) in some sections, is mainly represented by alluvial sedimentation associated with calc-alkaline magmatism. A second stage (late Artinskian–early Kungurian), represented by alluvial, lacustrine and palustrine sediments with intercalations of calc-alkaline volcanic beds, shows a clear upward aridification trend probably related to the late Paleozoic icehouse-greenhouse transition. The third and final stage (Wordian-Capitanian) comprised of alluvial deposits with intercalations of alkaline and mafic beds, rarely deposited in the Cantabrian Mountains, and underwent significant pre- and Early Mesozoic erosion in some segments of the Pyrenees. This third stage can be related to a transition towards the Pangea Supercontinent breakup, not generalized until the Early/Middle Triassic at this latitude because the extensional process stopped about 10 Myr (Pyrenees) to 30 Myr (Cantabrian Mountains). When compared to other well-dated basins near the paleoequator, the tectono-sedimentary and climate evolution of lower-middle Permian basins in Western and Central Europe shows common features. Specifically, we identify coeval periods with magmatic activity, extensional tectonics, high subsidence rates and thick sedimentary record, as well as prolonged periods without sedimentation. This comparison also identifies some evolutionary differences between Permian basins that could be related to distinct locations in the hinterland or foreland of the Variscan orogen. Our data provide a better understanding of the major crustal re-equilibration and reorganization that took place near the equator in Western-Central Europe during the post-Variscan period. • The beginning of the Iberian Variscan orogenic collapse is late Carboniferous in the hinterland and early Permian towards the foreland. • Variscan orogenic collapse is associated with calc-alkaline magmatism that shifts to alkaline magmatism in middle Permian times. • The beginning of the Alpine cycle of sedimentation in the whole Pyrenean ranges occurred as three main Permian tectono-sedimentary extensional phases. • The Permian tectono-sedimentary evolution of the Pyrenean ranges shows common features to the ones of Central and W Europe basins.

Checklist of the vascular plants of the Cantabrian Mountains

We present the first standardized list of the vascular flora of the Cantabrian Mountains, a transitional zone between the Eurosiberian and Mediterranean biogeographic regions in northwestern Spain. The study area comprises 15000 km2 divided in UTM grid cells of 10 km x 10 km, for which we revised occurrence data reported in the Spanish Plant Information System (Anthos) and the online database of Iberian and Macaronesian Vegetation (SIVIM). We used a semi-automatic procedure to standardize taxonomic concepts into a single list of names, which was further updated by expert-based revision with the support of national and regional literature. In the current version, the checklist of the Cantabrian Mountains contains 2338 native species and subspecies, from which 56 are endemic to the study area. The nomenclature of the checklist follows Euro+Med in 97% of taxa, including annotations when other criteria has been used and for taxa with uncertain status. We also provide a list of 492 non-native taxa that were erroneously reported in the study area, a list of local apomictic taxa, a phylogenetic tree linked to The Plant List, a standardized calculation of Ellenberg Ecological Indicator Values for 80% of the flora, and information about life forms, IUCN threat categories and legal protection status. Our review demonstrates how the Cantabrian mountains represent a key floristic region in southern Europe and a relevant phytogeographical hub in south-western Europe. The checklist and all related information are freely accessible in a digital repository for further uses in basic and applied research

And yet, migration, population growth or mortality are not balanced among Cantabrian brown bear subpopulations. Reply to Blanco et al (2020).

In a recent paper, we presented new evidence and provided new insights on the status of Cantabrian brown bear subpopulations, relevant for this species conservation. Namely, we revealed the likely phylogeographic relation between eastern Cantabrian subpopulation and the historical Pyrenean population. We have also detected an asymmetric flow of alleles and individuals from the eastern to the western subpopulation, including seven first-generation male migrants. Based on our results and on those of previous studies, we called the attention to the fact that Eastern Cantabrian brown bears might be taking advantage of increased connectivity to avoid higher human pressure and direct persecution in the areas occupied by the eastern Cantabrian subpopulation. In reply, Blanco et al (2020) [11] have criticized our ecological interpretation of the data presented in our paper. Namely, Blanco and co-authors criticize: (1) the use of the exodus concept in the title and discussion of the paper; (2) the apparent contradiction with source-sink theory; (3) the apparent overlooking of historical demographic data on Cantabrian brown bear and the use of the expression of population decline when referring to eastern subpopulation. Rather than contradicting the long and growing body of knowledge on the two brown bear subpopulations, the results presented in our paper allow a new perspective on the causes of the distinct pace of population growth of the two brown bear subpopulations in the last decades. Here, we reply to the criticisms by: clarifying our ecological interpretation of the results; refocusing the discussion on how the new genetic data suggest that currently, the flow of individuals and alleles is stronger westward, and how it may be linked to direct persecution and killing of brown bears. We provide detailed data on brown bear mortality in the Cantabrian Mountains and show that neither migration, gene flow, population increase nor mortality are balanced among the two subpopulations.

The Upper Devonian of the river Sil area: a stratigraphic correlation between León and Asturias, northern Spain

We have studied the Upper Devonian succession of the river Sil area divided into five sections along a SW-NE transect. Thirteen lithofacies types have been identified based on lithology and sedimentological structures. They have been organised into facies associations representing depositional environments from the fluviomarine zone of the nearby part of the basin towards the distal offshore zone. Erosion surfaces and sequence boundaries have been identified and the succession is connected to the Upper Devonian sequence stratigraphic model of the southern Cantabrian Mountains and the Upper Devonian succession of the Coastal Ranges of Asturias in the north. The main portion of the Upper Devonian succession of the Sil area can be correlated with the Nocedo Formation, Gordón Member (sequence A) of early Frasnian age. In the south-westernmost sections of the Sil area parts of the Fueyo and Ermita formations are exposed; they constitute sequence C of early Famennian age. The Upper Devonian Unconformity separates these thick Frasnian-Famennian coarsening upward sequences from the overlying extensive Famennian-Tournaisian condensed succession of the Llombera Beds (sequence D).

Evidence for genetic isolation and local adaptation in the field cricket Gryllus campestris.

Understanding how species can thrive in a range of environments is a central challenge for evolutionary ecology. There is strong evidence for local adaptation along large-scale ecological clines in insects. However, potential adaptation among neighbouring populations differing in their environment has been studied much less. We used RAD sequencing to quantify genetic divergence and clustering of ten populations of the field cricket Gryllus campestris in the Cantabrian Mountains of northern Spain, and an outgroup on the inland plain. Our populations were chosen to represent replicate high and low altitude habitats. We identified genetic clusters that include both high and low altitude populations indicating that the two habitat types do not hold ancestrally distinct lineages. Using common-garden rearing experiments to remove environmental effects, we found evidence for differences between high and low altitude populations in physiological and life-history traits. As predicted by the local adaptation hypothesis, crickets with parents from cooler (high altitude) populations recovered from periods of extreme cooling more rapidly than those with parents from warmer (low altitude) populations. Growth rates also differed between offspring from high and low altitude populations. However, contrary to our prediction that crickets from high altitudes would grow faster, the most striking difference was that at high temperatures, growth was fastest in individuals from low altitudes. Our findings reveal that populations a few tens of kilometres apart have independently evolved adaptations to their environment. This suggests that local adaptation in a range of traits may be commonplace even in mobile invertebrates at scales of a small fraction of species' distributions.

The unevenness of the north Iberian crustal root, a snapshot of an elusive stage in margin reactivation

AbstractCrustal roots are identified in collision chains worldwide. Frequently mirroring the summits of mountain systems, they elegantly encapsulate the concept of isostasy. The rugged topography of northern Iberia results from convergence with the European plate during the Alpine orogeny that formed the Pyrenean-Cantabrian mountain range. From east to west, the range comprises three distinct parts: the Pyrenees, the Basque Cantabrian region, and the Cantabrian Mountains. The identification of the Pyrenean root in the 1980s and the observation of a similar geometry beneath the Cantabrian range in the 1990s gave place to the current view of crustal thickening as a continuous feature, resulting from the northward subduction of Iberian crust. Recent developments in rift architecture have delivered a complex rifting template for the area prior to convergence, and contrasting views based on two-dimensional restorations have led to a debate over its evolution. A crucial geophysical constraint is Moho topography. Using two different data sets and techniques, we present the most accurate Moho surface to date, evidencing abrupt changes throughout the orogen. The complexity of hyperextended margins underlies the current Moho topography, and this is ultimately transferred to the nonuniform orogenic pattern found in northern Iberia.

Gravitational slope processes triggered by past earthquakes on the Western Cantabrian Mountains (Sierra de la Sobia, Northern Spain)

Sierra de la Sobia is a linear mountain range of arcuate shape, located west of the Cantabrian Mountains. The long-lived crustal León Fault runs along its western hillslope, and its trace is partially covered by multiple rock-avalanches. Here we discuss if recurrent paleo-earthquakes in the M6+ range could have acted as the triggering factor for rock-avalanches in a region where the historical and instrumental seismic records only include seismic events up to Ms 4.6. Evidence concurring with a coseismic origin includes: (i) kinematic of current minor transverse and parallel faults to Sierra de la Sobia being consistent with a horizontal North-South compression of the Cantabrian Arc; (ii) slopes of the depletion zones that would become unstable if horizontal seismic ground rose 0.10–0.15 g; and (iii) block size-reduction by dynamic fragmentation creating block size distribution with fractal dimension, ranging between 2.24 and 2.70. U/Th dating of seven calcite precipitates coating the blocks of cemented rock-avalanche deposits suggesting that cementation has taken place in multiple episodes since MIS-9a. Neotectonics of Sierra de la Sobia are expressed in subtle changes in relief after extremely rapid co-seismic events, with average recurrence intervals much longer than the time covered by the regional historical and instrumental period.

Devonian brachiopods of the Cantabrian Mountains (Northern Spain). 12) Ferronirhynchia new genus, an Upper Emsian rhynchonellid (Trigonirhynchiidae)

The taxonomic status of the subfamily Trigonirhynchiinae is discussed based on the morphological features, together with the geographic and the stratigraphic distribution of the type genus Trigonirhynchia Cooper. The new genus, Ferronirhynchia n. gen., including the type species F. pulgari n. sp., is proposed. The new taxon, close to Trigonirhynchia, occurs in upper Emsian beds of the Moniello Formation, in Asturias, serotinus/patulus conodont zones, Faunal Intervals 14 to 16a. The ontogeny and palaeoecology of F. pulgari are analyzed. Growth of the new species is bicyclic. Juvenile forms are low and biconvex displaying sharp commissures. Adult forms are high, dorsi-biconvex, geniculate, with abrupt anterior and lateral margins. Ferronirhynchia pulgari is an opportunistic species, often found in paraautochtonous rhynchonellid assemblages that occur in quiet and muddy deposits formed below the wave-base level near or in reefal environments in the Cantabrian platfom. Shells of the new species supported a variety of small epizoans, commensalists or mutualists, mostly reticulate bryozoans, serpulid and other tubeworms, and auloporids. This life habit favoured the epizoans to escape from burial in muddy bottoms.