El Soplao Research Articles

Symbiosis between Cretaceous dinosaurs and feather-feeding beetles

Extant terrestrial vertebrates, including birds, have a panoply of symbiotic relationships with many insects and arachnids, such as parasitism or mutualism. Yet, identifying arthropod-vertebrate symbioses in the fossil record has been based largely on indirect evidence; findings of direct association between arthropod guests and dinosaur host remains are exceedingly scarce. Here, we present direct and indirect evidence demonstrating that beetle larvae fed on feathers from an undetermined theropod host (avian or nonavian) 105 million y ago. An exceptional amber assemblage is reported of larval molts (exuviae) intimately associated with plumulaceous feather and other remains, as well as three additional amber pieces preserving isolated conspecific exuviae. Samples were found in the roughly coeval Spanish amber deposits of El Soplao, San Just, and Peñacerrada I. Integration of the morphological, systematic, and taphonomic data shows that the beetle larval exuviae, belonging to three developmental stages, are most consistent with skin/hide beetles (family Dermestidae), an ecologically important group with extant keratophagous species that commonly inhabit bird and mammal nests. These findings show that a symbiotic relationship involving keratophagy comparable to that of beetles and birds in current ecosystems existed between their Early Cretaceous relatives.

Barklice (Insecta: Psocodea) from Early Cretaceous resiniferous forests of Iberia (Spanish amber): New Troctomorpha and a possible Psocomorpha

Psocids, commonly known as barklice, are insects belonging to the order Psocodea, together with the parasitic lice. They usually inhabit forest litter or the bark of tree trunks and branches, showing grazing herbivorous or detritivorous feeding habits. The Cretaceous psocid record is diverse, containing more than 70 described species. Here, we present new psocids (Troctomorpha and possible Psocomorpha) from two Spanish amber outcrops, both Albian (Lower Cretaceous): El Soplao and Ariño. We describe the two new species Azarpsocus anjana Álvarez-Parra and Nel sp. nov. (Manicapsocidae) and Burmacompsocus ojancano Álvarez-Parra and Nel sp. nov. (Compsocidae), and the morphotype Ariño that might belong to Psocomorpha. We discuss the taxonomic placement of the studied specimens and comment on the palaeobiogeography of the Cretaceous psocids. The Cretaceous barklice fauna from Iberia shows more similarities with that from Lebanese (Barremian) and Burmese (Cenomanian) ambers than with that from the palaeogeographically closer French amber (Cenomanian). This finding has been also reported in other insect groups from Spanish amber, and might be the consequence of several factors, such as the palaeoenvironmental conditions of the ecosystems, the palaeogeographical position of the Iberia Island during the latest Jurassic, closer to Gondwana than to Laurasia, and oceanic currents that facilitated or hindered the displacement of insect fauna between continental masses.

A new genus of dance fly (Diptera: Empidoidea: Hybotidae) from Cretaceous Spanish ambers and introduction to the fossiliferous amber outcrop of La Hoya (Castellón Province, Spain).

Hybotidae fly species, also known as dance flies, in Cretaceous ambers have been described from Lebanon, France, Myanmar, Russia, and Canada. Here we describe Grimaldipeza coelica gen. et sp. n., and recognize another two un-named species, in Spanish amber from the middle Albian El Soplao and lower Cenomanian La Hoya outcrops. The fore tibial gland is present in the new genus, which is characteristic of the family Hybotidae. We compare Grimaldipeza coelica gen. et sp. n. with the holotypes of Trichinites cretaceus Hennig, 1970 and Ecommocydromia difficilis Schlüter, 1978, and clarify some morphological details present in the latter two species. Further taxonomic placement beyond family of the here described new genus was not possible and remains incertae sedis within Hybotidae until extant subfamilies are better defined. We provide new paleoecological data of the hybotids, together with paleogeographical and life paleoenvironmental notes. A table with the known Cretaceous Hybotidae is provided. Furthermore, the La Hoya amber-bearing outcrop is described in detail, filling the information gap for this deposit.

The 8.2 ka event in northern Spain: timing, structure and climatic impact from a multi-proxy speleothem record

Abstract. The 8.2 ka event is regarded as the most prominent climate anomaly of the Holocene and is thought to have been triggered by a meltwater release to the North Atlantic that was of sufficient magnitude to disrupt the Atlantic Meridional Overturning Circulation (AMOC). It is most clearly captured in Greenland ice-core records, where it is reported as a cold and dry anomaly lasting ∼ 160 years, from 8.25 ± 0.05 until 8.09 ± 0.05 ka (Thomas et al., 2007). It is also recorded in several archives in the North Atlantic region; however, its interpreted timing, evolution and impacts vary significantly. This inconsistency is commonly attributed to poorly constrained chronologies and/or inadequately resolved time series. Here we present a high-resolution speleothem record of early Holocene palaeoclimate from El Soplao Cave in northern Spain, a region pertinent to studying the impacts of AMOC perturbations on south-western Europe. We explore the timing and impact of the 8.2 ka event on a decadal scale by coupling speleothem stable carbon and oxygen isotopic ratios, trace element ratios (Mg / Ca and Sr / Ca), and growth rate. Throughout the entire speleothem record, δ18O variability is related to changes in effective recharge. This is supported by the pattern of changes in δ13C, Mg / Ca and growth rate. The 8.2 ka event is marked as a centennial-scale negative excursion in El Soplao δ18O, starting at 8.19 ± 0.06 ka and lasting until 8.05 ± 0.05 ka, suggesting increased recharge at the time. Although this is supported by the other proxies, the amplitude of the changes is minor and largely within the realm of variability over the preceding 1000 years. Further, the shift to lower δ18O leads the other proxies, which we interpret as the imprint of the change in the isotopic composition of the moisture source, associated with the meltwater flux to the North Atlantic. A comparison with other well-dated records from south-western Europe reveals that the timing of the 8.2 ka event was synchronous, with an error-weighted mean age for the onset of 8.23 ± 0.03 and 8.10 ± 0.05 ka for the end of the event. This compares favourably with the North Greenland Ice Core Project (NGRIP) record. The comparison also reveals that the El Soplao δ18O is structurally similar to the other archives in south-western Europe and the NGRIP ice-core record.

A review of the Cretaceous genus Eltxo (Diptera: Cecidomyiidae) with description of the new species Eltxo grimaldii from El Soplao amber

A new species, Eltxo grimaldii sp. nov., is described from Spanish Lower Cretaceous (middle Albian) amber from El Soplao, based on a single female. The new species is compared with the other only known species of the genus, Eltxo cretaceus Arillo & Nel, 2000, based on a single male specimen also found in Spanish amber, but slightly younger (Peñacerrada I amber; upper Albian). The holotype of E. cretaceus is reviewed and its description corrected and expanded, providing the first micrographs of its anatomical features. The holotype of the new fossil species is the only female specimen known of the cecidomyiid tribe Amediini Jaschhof, 2021, a tribe recently described after changes of taxonomic attribution of the genus Eltxo during the last 20 years.

Beaded lacewings (Neuroptera: Berothidae) in amber from the Lower Cretaceous of Spain

Five new beaded lacewings (Neuroptera: Berothidae) are described from ca. 105 Ma Spanish amber. A new genus and species, Cantabroberotha soplaensis gen. et sp. nov., are erected based on a complete amber specimen from the El Soplao outcrop (Cantabria, northern Spain). Four indeterminate berothids based on incomplete specimens are described from Peñacerrada I amber (Burgos, northern Spain). One of these provides a rare instance of an amber fossil being partially preserved as an impression rather than as a complete inclusion. This was the result of the lacewing not fully penetrating into a resin flow, its wings getting caught on the resin surface and leaving an imprint. The preservation of this delicate impression fossil allows us to infer that a low grade transport likely occurred, at least partly, during the biostratinomic phase of the genesis of the Peñacerrada I amber deposit, similar to what was inferred for the El Soplao amber deposit. Moreover, one of the incomplete berothid inclusions has an indeterminate, likely immature mesostigmatan mite attached to the proximal part of its hind wing, most parsimoniously resulting from a symbiotic interaction, probably phoresy.

Early Cretaceous termites in amber from northern Spain (Isoptera)

Two virtually complete termites in Lower Cretaceous amber from the Peñacerrada I outcrop, Spain, are described and figured, representing the most well-preserved Isoptera yet discovered from the Albian stage. The material is described as Ithytermes montoyai gen. et sp. nov., and is similar in many details to the slightly younger Krishnatermes yoddha Engel, Barden, and Grimaldi from northern Myanmar amber. Given the presence of distinct soldiers in this grade of Cretaceous termites, it is likely that I. montoyai also exhibited such a tripartite caste system. In addition to the type material of I. montoyai, two fragmentary termites are recorded for the first time in Albian amber from the El Soplao outcrop, and in the few preserved details these taxa are not conspecific with the former.

<p><strong>A new dustywing (Neuroptera: Coniopterygidae) from the Early Cretaceous amber of Spain</strong></p>

A new Cretaceous dustywing, Soplaoconis ortegablancoi gen. et sp. nov. (Neuroptera: Coniopterygidae), is described from four specimens preserved in Early Cretaceous (Albian, ~105Ma) El Soplao amber (Cantabria, northern Spain). Two additional specimens are assigned to this new taxon. A crossvenational abnormality on an area of diagnostic significance from one of the holotype’s forewings provides a reminder of the importance of not ruling out character plasticity or teratoses when evaluating palaeodiversity. A comment on the possible palaeoecological significance of the co-occurrence as syninclusions of plant trichomes with the holotype of S. ortegablancoi and seven of the eleven described Burmese amber dustywing species is provided.

<p><strong>The first Cretaceous beetle from Azerbaijan:<em> Katyacantharis zherikhini</em> gen. et sp. n. (Coleoptera, Cantharidae) from Cenomanian Agdzhakend amber</strong></p>

Cantharidae, or soldier-beetles, have so far been described from only two Cretaceous amber deposits. One genus and one species was reported from Spanish amber (El Soplao: Peris & Fanti, 2018) and six genera and seven species from Burmese amber (Hukawng Valley: Poinar & Fanti, 2016; Hsiao et al., 2017; Fanti & Ellenberger, 2017; 2018; Fanti at al., 2018). Other Cretaceous ambers, except for Lebanese amber (Kirejtshuk & Azar, 2013) seemed to lack soldier-beetles (Rasnitsyn et al., 2016).

Molliberus albae gen. et sp. nov., the oldest Laurasian soldier beetle (Coleoptera: Cantharidae) from the Lower Cretaceous Spanish amber

A new soldier beetle (Coleoptera: Cantharidae), Molliberus albae gen. et sp. nov., is described and illustrated from the El Soplao Lower Cretaceous (lower Albian) amber deposit in northern Spain. This is the first fossil species in the family to be described from the Spanish amber and the oldest representative in Europe. The new species shows affinities with the Late Cretaceous (early Cenomanian) species from Myanmar, and the fossil is compared with the other Cretaceous fossil species. The elongate prognathous head is a diagnostic character of Molliberus albae gen. et sp. nov., from which it may be inferred that this species fed on pollen or nectar.

Replication and reinsertion of stalagmites sampled for paleoclimatic purposes

Sampling stalagmites for paleoclimatic study can enter into conflict with preserving the beauty and integrity of caves. To minimize this impact, a variety of sampling strategies have been used by researches aware of cave-conservation issues. Based on our experience in two caves (El Soplao and La Buenita, Cantabria, N Spain), we propose to apply molding and casting laboratory techniques to create replicas of stalagmites, placing the replicas back in the original cave locations so that the impact of sampling to the cave is severely reduced. We provide detailed descriptions of the molding and casting methods, which vary depending on stalagmite size. For relatively small specimens (less than ~35 cm tall), we use a single-piece mold and two jackets. For larger stalagmites (~40-70 cm tall), we use a two-piece mold and two jackets. In a first casting step, we obtain a master piece in dental plaster that is preserved. In a subsequent casting step, we use epoxy resin to generate the replica that will be placed in the cave. We use extra-hard plaster coated with epoxy resin to fix the replicas to their original substrates. Both the epoxy resin and plaster are carefully dyed to match the original surface texture and color of the sampled stalagmites. Once in place, the stalagmite replicas are almost indistinguishable from the natural specimens.

A new genus of silken-fungus beetle (Coleoptera: Cryptophagidae) from the Spanish Cretaceous amber

The Cretaceous new species and genus Albocryptophagus cantabricus gen. et sp. n. is described based on a fossil specimen from the El Soplao amber deposit (Spain). The new genus is similar to the extant genera Cryptophagus and Micrambe, but differs from them in the transverse pedicel, anterior angles of pronotum, pronotal margin unmodified, pronotal pits absent. Albocryptophagus gen. n. is undoubtedly the most ancient representative for the subfamily Cryptophaginae described up today. Because the saproxylic habits in recent species of the family, a similar behavior is inferred for this new fossil. It is a new example that agrees with the idea that fossil beetles from Mesozoic ambers are characterized by a saproxylic lifestyle.

A real-time underground environment monitoring system for sustainable tourism of caves

In this paper, a real-time monitoring system is presented to be used for environmental parameters measurement in tourist caves that can be employed for getting a sustainable tourism. The system allows the registration of a lot of metadata (temperature, relative humidity, wind speed and direction, CO2, atmospheric pressure, rain, presence and visitor count) and it shows them via the Internet in real time anywhere. The system reports the data registered and stored as metadata in a database online. In the ”El Soplao” Cave in the North of Spain, this system, permits a high level of control and security of the influence of visitors on a day to day and the temporal evolution to medium and long term. These measurements allow developing a sustainable and profitable system where heritage management and tourism exploitation acquire a subordinate commitment to the welfare of the natural asset (Cave-Mine “El Soplao”); the alteration of the fragile microclimate inside the cave can damage or destroy the specific geologic formations that make the touristic cave. After the visits, the company managing the cave takes in charge monitoring the environmental parameters of the cave to regulate future visits. The temperature in the cave has ranges between 11 and 13.5 °C, a seasonal quasi-periodic maximum variation of ± 0.5 °C and depending on the temperature outside the cave and number of visitors; it is difficult to associate one with another because both happen in the same month. The relative humidity is around 70–95%, it has no correlation with the number of visitors accessing the cavity. The CO2 concentration in air is around 400–1000 ppm; it has a clear correlation with the number of visitors and cave area (the deepest present's higher level CO2). In conclusion, a cave is visited as long as its microclimate is maintained, thus the real-time system developed has been conceptualized for monitoring over time the relationship between the cave environment and a sustainable tourism. Monitoring can help to preserve the specific geologic formation and therefore to keep the touristic interest of the cave.

Hydrochemical controls on aragonite versus calcite precipitation in cave dripwaters

Despite the paleoclimatic relevance of primary calcite to aragonite transitions in stalagmites, the relative role of fluid Mg/Ca ratio, supersaturation and CO32− concentration in controlling such transitions is still incompletely understood. Accordingly, we have monitored the hydrochemistry of 50 drips and 8 pools that are currently precipitating calcite and/or aragonite in El Soplao and Torca Ancha Caves (N. Spain), investigating the mineralogy and geochemistry of the CaCO3 precipitates on the corresponding natural speleothem surfaces. The data reveal that, apart from possible substrate effects, dripwater Mg/Ca is the only obvious control on CaCO3 polymorphism in the studied stalagmites and pools, where calcite- and aragonite-precipitating dripwaters are separated by an initial (i.e. at stalactite tips) Mg/Ca threshold at ≈1.1mol/mol. Within the analyzed ranges of pH (8.2–8.6), CO32− concentration (1–6mg/L), supersaturation (SIaragonite: 0.08–1.08; SIcalcite: 0.23–1.24), drip rate (0.2–81drops/min) and dissolved Zn (6–90μg/L), we observe no unequivocal influence of these parameters on CaCO3 mineralogy. Despite the almost complete overlapping supersaturations of calcite- and aragonite-precipitating waters, the latter are on average less supersaturated because the waters having Mg/Ca above ∼1.1 have mostly achieved such high ratios by previously precipitating calcite. Both calcite and aragonite precipitated at or near oxygen isotopic equilibrium, and Mg incorporation into calcite was consistent with literature-based predictions, indicating that in the studied cases CaCO3 precipitation was not significantly influenced by strong kinetic effects. In the studied cases, the calcites that precipitate at ∼11°C from dripwaters with initial Mg/Ca approaching ∼1.1 incorporate ∼5mol% MgCO3, close to the published value above which calcite solubility exceeds aragonite solubility, suggesting that aragonite precipitation in high-relative-humidity caves is favored from a solubility viewpoint. We also show that unaccounted CaCO3 precipitation in intermediate sampling containers and splash effects may in cases result in underestimating dripwater Ca concentration and alkalinity, potentially leading to incorrect conclusions regarding the role of fluid Mg/Ca ratio and supersaturation on CaCO3 mineralogy. A simple way to elude the first effect is by taking water samples directly from stalactites and by titrating alkalinity in the same containers used to collect dripwaters.

In situ Raman characterization of minerals and degradation processes in a variety of cultural and geological heritage sites

We test the capabilities of in situ Raman spectroscopy for non-destructive analysis of degradation processes in invaluable masterpieces, as well as for the characterization of minerals and prehistoric rock-art in caves. To this end, we have studied the mechanism of decay suffered by the 15th-century limestone sculptures that decorate the retro-choir of Burgos Cathedral (N Spain). In situ Raman probe detected hydrated sulfate and nitrate minerals on the sculptures, which are responsible for the decay of the original limestone. In addition, in situ Raman analyses were performed on unique speleothems in El Soplao Cave (Cantabria, N Spain) and in the Gruta de las Maravillas (Aracena, SW Spain). Unusual cave minerals were detected in El Soplao Cave, such as hydromagnesite (Mg5(CO3)4(OH)2·4H2O), as well as ferromanganese oxides in the black biogenic speleothems recently discovered in this cavern. In the Gruta de las Maravillas, gypsum (CaSO4·2H2O) was identified for the first time, as part of the oldest cave materials, so providing additional evidence of hypogenic mechanisms that occurred in this cave during earlier stages of its formation. Finally, we present preliminary analyses of several cave paintings in the renowned “Polychrome Hall” of Altamira Cave (Cantabria, N. Spain). Hematite (Fe2O3) is the most abundant mineral phase, which provides the characteristic ochre-reddish color to the Altamira bison and deer paintings. Thus, portable Raman spectroscopy is demonstrated to be an analytical technique compatible with preserving our cultural and natural heritage, since the analysis does not require physical contact between the Raman head and the analyzed items.

New species of fossil oribatid mites (Acariformes, Oribatida), from the Lower Cretaceous amber of Spain

Mites are relatively common and diverse in fossiliferous ambers, but remain essentially unstudied. Here, we report on five new oribatid fossil species from Lower Cretaceous Spanish amber, including representatives of three superfamilies, and five families of the Oribatida. Hypovertex hispanicus sp. nov. and Tenuelamellarea estefaniae sp. nov. are described from amber pieces discovered in the San Just outcrop (Teruel Province). This is the first time fossil oribatid mites have been discovered in the El Soplao outcrop (Cantabria Province) and, here, we describe the following new species: Afronothrus ornosae sp. nov., Nothrus vazquezae sp. nov., and Platyliodes sellnicki sp. nov. The taxa are discussed in relation to other fossil lineages of Oribatida as well as in relation to their modern counterparts. Some of the inclusions were imaged using confocal laser scanning microscopy, demonstrating the potential of this technique for studying fossil mites in amber. A table, including all the known Mesozoic oribatid mites preserved in amber, is included.

Economic Valuation of Mining Heritage from a Recreational Approach: Application to the Case of El Soplao Cave in Spain (Geosite UR004)

Heritage tourism can increase incomes and stimulate the economy in former mining areas. Recreational tourism is one of the main sources of value of heritage. People from urban areas are willing to pay for access to these tourism options. The measurement of the economic impact of this availability is one of the main problems to confront, due to the immeasurable possibilities of heritage resources. The use of non-market values and their estimation by means of revealed preference methods should help to assess the economic value of this sort of resources from a recreational perspective. The travel cost method (TCM) is widely used to value areas with recreational uses, such as lakes, beaches or forests, but there are not references to previous applications of this methodology in the field of mining heritage. In this work, TCM has been applied to obtain the economic value of El Soplao Cave (Geosite UR004, Cantabria, Spain) as a recreational site, providing an estimated result of 34,961,162 euros.

Do two-level systems and boson peak persist or vanish in hyperaged geological glasses of amber?

In this work, we extend, review and jointly discuss earlier experiments conducted by us in hyperaged geological glasses, either in Dominican amber (20 million years old) or in Spanish amber from El Soplao (110 million years old). After characterization of their thermodynamic and elastic properties (using Differential Scanning Calorimetry around the glass-transition temperature, and measuring mass density and sound velocity), their specific heat was measured at low and very low temperatures. By directly comparing pristine amber samples (i.e. highly stabilized polymer glasses after ageing for millions of years) to the same samples after being totally or partially rejuvenated, we have found that the two most prominent universal “anomalous” low-temperature properties of glasses, namely the tunnelling two-level systems and the so-called “boson peak”, persist essentially unchanged in both types of hyperaged geological glasses. Therefore, non-Debye low-energy excitations of glasses appear to be robust, intrinsic properties of non-crystalline solids which do not vanish by accessing to very deep states in the potential energy landscape.

New Eoptychoptera (Insecta: Diptera, Ptychopteridae) from the Lower Cretaceous of Spain

A new species, Eoptychoptera cantabrica sp. nov. is described from the Albian El Soplao amber-bearing deposits based on a single male with an elongated proboscis, unknown among extant members of Ptychopteridae. It represents the youngest record of the species-diverse genus Eoptychoptera. A pupa of Eoptychoptera sp. with a long respiratory horn, typical of extant ptychopterids, is described from Las Hoyas limestones, where adult fossil ptychopterids have yet to be discovered. A key to species of Eoptychoptera, based on wing venation, and a distribution map of Cretaceous Ptychopteridae are provided. The climatic preferences and mouthparts of Mesozoic and recent Ptychopteridae are discussed.

A defensive behavior and plant-insect interaction in Early Cretaceous amber – The case of the immature lacewing Hallucinochrysa diogenesi

Amber holds special paleobiological significance due to its ability to preserve direct evidence of biotic interactions and animal behaviors for millions of years. Here we review the finding of Hallucinochrysa diogenesi Pérez-de la Fuente, Delclòs, Peñalver and Engel, 2012, a morphologically atypical larva related to modern green lacewings (Insecta: Neuroptera) that was described in Early Cretaceous amber from the El Soplao outcrop (northern Spain). The fossil larva is preserved with a dense cloud of fern trichomes that corresponds to the trash packet the insect gathered and carried on its back for camouflaging and shielding, similar to that which is done by its extant relatives. This finding supports the prominent role of wildfires in the paleoecosystem and provides direct evidence of both an ancient plant–insect interaction and an early acquisition of a defensive behavior in an insect lineage. Overall, the fossil of H. diogenesi showcases the potential that the amber record offers to reconstruct not only the morphology of fossil arthropods but, more remarkably, their lifestyles and ecological relationships.