Search publications of the members of the Royal Belgian institute of natural Sciences
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The Ostracod Clumped-Isotope Thermometer: A Novel Tool to Accurately Quantify Continental Climate Changes
- This study presents a methodological advancement in the field of clumped-isotope (∆47) thermometry, specifically tailored for application to freshwater ostracods. The novel ostracod clumped isotope approach enables quantitative temperature and hydrological reconstruction in lacustrine records. The relationship between ∆47 and the temperature at which ostracod shell mineralized is determined by measuring ∆47 on different species grown under controlled temperatures, ranging from 4 ± 0.8 to 23 ± 0.5ºC. The excellent agreement between the presented ∆47 ostracod data and the monitored temperatures confirms that ∆47 can be applied to ostracod shells and that a vital effect is absent outside the uncertainty of measurements. Results are consistent with the carbonate clumped-isotope unified calibration (Anderson et al., 2021, https://doi.org/10.1029/2020gl092069), therefore, an ostracod-specific calibration is not needed. The ostracod clumped-isotope thermometer represents a powerful tool for terrestrial paleoclimate studies all around the world, as lakes and ostracods are found in all climatic belts.
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Evidence for a single population expansion event across 24,000 km: the case of the deep‑sea scavenging amphipod Abyssorchomene distinctus
- Anthropogenic activities such as mining pose a putative threat to deep-sea ecosystems and baseline studies of key indicator species are required to assess future loss of biodiversity. We examined population genetic structure, connectivity, cryptic diversity and phylogeography of the deep-sea scavenging amphipod, Abyssorchomene distinctus, using DNA sequence data (mitochondrial COI and nuclear 28S genes) from 373 specimens collected from six abyssal basins. We observed a striking absence of cryptic diversity, suggesting a single, widely distributed species in the Pacifc and Indian Ocean. A single event of population expansion across distances up to 24,000 km is further supported by a main ancestral haplotype in the star-like shaped COI haplotype network, a skewed nucleotide mismatch distribution and deviations from evolutionary neutrality tests. In the Pacifc, A. distinctus showed weak genetic population structure and low diferentiation between the basins of the Clarion-Clipperton Zone and the DISCOL Experimental Area, suggesting a possible higher chance of recovery from deep-sea mining impacts. However, since our data indicate a single recent historic population expansion event, A. distinctus populations will likely be afected to unknown extents, as the exact drivers shaping distribution and dispersion of A. distinctus are still unclear
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infraFADA: Upgrading the taxonomic backbone of global freshwater animal biodiversity research infrastructures
- The current Freshwater Animal Diversity Assessment (FADA) comprises an extensive set of global taxa lists for freshwater animal groups. At present, more than 125 thousand described freshwater animal species in more than 11 thousand genera have been documented. However, taxonomy is a living scientific discipline, where new taxa are continuously being described, and existing taxa are being placed in new taxonomic positions. Therefore, after a period of relative inactivity, the BELSPO (Belgian Science Policy) project “infraFADA” (2023-2026) re-establishes the global FADA consortium of taxonomic experts, so that all taxa lists will be brought up to date, both technically and in terms of content. infraFADA will develop a living, updated, and global FADA database, fully in open access and according to the FAIR principles. The infraFADA database is intended for use and consultation by the scientific freshwater community, as well as for interested stakeholders, for example, freshwater ecosystem managers, biodiversity conservationists, and others. Most importantly, FADA will also serve as a taxonomic backbone for other global biodiversity data infrastructures, such as the Catalogue of Life (CoL), the Global Biodiversity Information Facility (GBIF), the Freshwater Information Platform (FIP), and others. As such, FADA will provide a digital and living heritage of freshwater data, building bridges between science and society and helping to sustainably maintain freshwater resources.
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An endemic species flock of Candonidae Kaufmann, 1900 (Crustacea, Ostracoda) from wells in Benin (West Africa), with the description of a new subfamily, a new genus and five new species
- Between 2015 and 2022, over 200 wells were sampled in four catchment areas of Benin, using both Cvetkov plankton nets (funnel 200 μm mesh size, 150 μm below valve) and baited traps. As artificial wells serve as ecotones (interfaces between surface and groundwater ecosystems), the ostracod fauna is mostly represented by two families; Cyprididae (mainly epigeic) and Candonidae (hypogeic). Here, we describe a new subfamily of Candonidae from the wells in Benin, the Benincandoninae subfam. nov. Hotèkpo & Martens, represented by one genus, Benincandona gen. nov. Hotèkpo & Martens. we found 35 species belonging to this evolutionary radiation, of which we describe five new species: Benincandona martini gen. et spec. nov. Hotèkpo & Martens, B. ibikounlei gen. et spec. nov. Hotèkpo & Martens, B. sakitii gen. et spec. nov. Hotèkpo & Martens, B. cebios gen. et spec. nov. Hotèkpo & Martens and B. trapezoides gen. et spec. nov. Hotèkpo & Martens. The new subfamily and genus are characterised by a unique combination of characters, such as a seven-segmented antennula and a caudal ramus with a fully developed ramus, a single apical (anterior) claw and three short setae. Species within the genus can be distinguished by their carapace and hemipenis morphology, together with some limb characteristics. whereas extensive subterranean candonid radiations have previously been reported from Europe, North and Central America and Northwest Australia (Pilbara), this is the first time such a vast radiation of subterranean candonids is reported from (west) Africa.
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Local factors drive the richness, biomass and composition of benthic invertebrate communities in Neotropical reservoirs
- Dams affect aquatic biota in running water by altering the environmental dynamics. One of the communities affected are benthic invertebrates, that perform important functions such as nutrient cycling and energy transfer in reservoirs. We investigated the influence of the following factors: spatial, abiotic variables, reservoir characteristics and land use on the richness, biomass and composition of benthic invertebrates in 29 reservoirs in southern Brazil. Sediment samples and abiotic variables were collected in the littoral and profundal zones of reservoirs during the dry (July) and rainy (November) seasons in 2001. We used principal coordinates of neighbour matrices to obtain the spatial factors. We analysed the unique and overall effects of the four factors. We found that the factors analysed significantly influenced the composition and biomass of the invertebrates (22%). The percentage of variation explained by the unique effects of the different factors showed similar values, but the spatial factors showed the highest value (4%). This indicates that closer reservoirs have higher similarities in terms of composition and biomass of benthic invertebrates. On the other hand, the abiotic variables had the highest explained value when evaluating the overall effects (10%). Therefore, for invertebrate richness, only the reservoir characteristics were significant for the overall and unique effects (49%). More specifically, we observed lower taxon richness in older reservoirs, probably because the age of such artificial aquatic ecosystems influences other variables, which structure the benthic communities. In conclusion, the structure of benthic invertebrate communities in reservoirs of southern Brazil are mainly driven by spatial and reservoir characteristics.
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Environmental factors and UV exposure affect gene activity in the putative ancient asexual ostracod Darwinula stevensoni
- The non-marine ostracod Darwinula stevensoni (Ostracoda, Crustaceae) is one of the last remaining examples of an ancient asexual (Schön et al. 2009) and has probably abandoned sexual reproduction approximately 20 million years ago (Straub 1952). In spite of the limited genetic diversity of D. stevensoni, its cosmopolitan distribution in different aquatic habitats indicate that this species can survive asexually in the long-term, possibly because it developed a general purpose genotype (Van Doninck et al. 2002). To unravel the genetic background of this general purpose genotype, we have studied gene activity of D. stevensoni via the RNA sequencing of transcriptomes. The transcriptome is the collection of all active genes which have been transcribed from DNA to RNA under certain conditions. Statistically comparing the genetic composition of transcriptomes allows us to identify differences in active (or expressed) genes, which inform on host adaptations to specific conditions. We characterised transcriptomes of D. stevensoni from natural populations in Spain, England and Belgium. To summarize results in our multi-gene approach, the “gene ontology” (GO) classification system was used which divides genes across groups (“terms”) in accordance to the biological function, molecular pathway or cellular component they affect. Of the 5013 terms which were assessed regarding biological function, 49 were found to have significantly different gene expression between the three different populations. However, none of these terms could be directly linked to temperature-related functions, suggesting that differences in gene expression between natural D. stevensoni populations are more complex and do not only reflect adaptation to varying temperature ranges. Living D. stevensoni individuals from the Belgian population were also exposed to UV-radiation in the lab. In this experiment, we expected to find an increased activity of genes being related to the repair and preservation of DNA countering the effects of UV-radiation. Of the same 5013 analysed gene terms, only 9 showed a significant change in gene expression in response to UV-radiation. None of these gene term had known repair functions, potentially highlighting again more complex gene expression patterns in D. stevensoni than initially expected. More analyses are currently ongoing to unravel the functionality of the activated genes in more detail. We are also planning an experimental set up to directly study gene expression differences of D. stevensoni under different temperatures.
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infraFADA: Upgrading the taxonomic backbone of global freshwater animal biodiversity research infrastructures
- The current Freshwater Animal Diversity Assessment (FADA) comprises an extensive set of global taxa lists for freshwater animal groups. At present, more than 125 thousand described freshwater animal species in more than 11 thousand genera have been documented. However, taxonomy is a living scientific discipline, where new taxa are continuously being described, and existing taxa are being placed in new taxonomic positions. Therefore, after a period of relative inactivity, the BELSPO (Belgian Science Policy) project “infraFADA” (2023-2026) re-establishes the global FADA consortium of taxonomic experts, so that all taxa lists will be brought up to date, both technically and in terms of content. infraFADA will develop a living, updated, and global FADA database, fully in open access and according to the FAIR principles. The infraFADA database is intended for use and consultation by the scientific freshwater community, as well as for interested stakeholders, for example, freshwater ecosystem managers, biodiversity conservationists, and others. Most importantly, FADA will also serve as a taxonomic backbone for other global biodiversity data infrastructures, such as the Catalogue of Life (CoL), the Global Biodiversity Information Facility (GBIF), the Freshwater Information Platform (FIP), and others. As such, FADA will provide a digital and living heritage of freshwater data, building bridges between science and society and helping to sustainably maintain freshwater resources.
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Hematodinium perezi (Dinophyceae: Syndiniales) in Morocco: The First Record on the African Atlantic Coast and the First Country Record of a Parasite of the Invasive Non-Native Blue Crab Callinectes sapidus
- Dinoflagellates belonging to the genus Hematodinium are key parasites of marine crustaceans, primarily decapods. In this study, we document the first report of H. perezi Chatton & Poisson, 1930 on the African Atlantic coast. This is also the first parasite record in the invasive non-native Atlantic blue crab Callinectes sapidus Rathbun, 1896 in Morocco. Specimens of C. sapidus were sampled in winter 2023 from two Ramsar sites on the Moroccan Atlantic, namely Merja Zerga and Oualidia Lagoons, and were screened to detect the presence of parasites in their hemolymph. Based on staining fresh hemolymph smears, we did not detect Hematodinium in any of the 36 investigated individuals (20 and 16 from Merja Zerga and Oualidia Lagoons, respectively), probably due to methodological artifacts. The PCR-based method was revealed to be more accurate in diagnosing the Hematodinium parasite. It showed that at Merja Zerga Lagoon, 13 individuals of C. sapidus were infected by the parasite (prevalence: 65%) in comparison to four at Oualidia Lagoon (25%). Genetic analysis, based on the ITS1 rDNA gene from Hematodinium, confirmed the sequences as being those of Hematodinium perezi.
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High-resolution description of insular and fjordic benthic food webs along the West Antarctic Peninsula
- The West Antarctic Peninsula (WAP) is one of the most rapidly warming region on Earth. In this context, it is crucial to improve our understanding of the consequences of future changes in the local biotic and abiotic environments on marine ecosystem functioning. Here, we focused on food web structure of shallow-water benthic communities. In February 2023, the TANGO1 expedition, using a sailboat, brought nine Belgian scientists to the WAP. To assess the importance of environmental changes on local food web dynamics, five benthic communities were investigated, focusing on macroalgae forests (n=2) and sedimentary soft bottoms (n=3). These stations were distributed between two contrasted environments, Dodman Island (Grandidier Channel, 66°S) & Blaiklock Island (Bigourdan Fjord, 67.5°S). These two locations differed markedly in terms of sea-ice cover, and in terms of general hydrography (small island exposed to the Grandidier Channel’s currents VS fjord system surrounded by active glaciers). At each station, basal food sources (i.e. sediment-associated POM, water-column POM, macroalgae, microphytobenthos) as well as benthic invertebrates (435 individuals, 64 morphospecies) were sampled quantitatively to assess their biomass, and for later stable isotope analysis. Using stable isotope ratios of carbon, nitrogen and sulphur, and Bayesian tools, we aim to formally represent the communities in isotopic space, and to compare their topologies along the environmental gradient studied. These representations will then be used to test whether differences in food web structure reflect general community characteristics, such as the higher biomass of organisms measured in macroalgae forests, which also display the greatest species diversity.
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Otolith morphology of mesopelagic fishes collected from the Irminger Sea, North Atlantic Ocean
- A large series of otoliths of 16 mesopelagic teleost fish species from the Irminger Sea, North Atlantic Ocean, are described morphologically to investigate the ontogenetic and intraspecific variation. The results show that the surface morphology of the otoliths between young and adult specimens is variable, especially in the alepocephaliform (Normichthys operosus, Sagamichthys schnakenbecki, Xenodermichthys copei) and astronesthine (Borostomias antarcticus) species. The diagnostic features of the otoliths can be used to confirm the identity of the species, especially in myctophids, where confusion between Benthosema glaciale and Myctophum punctatum may be possible. A SEM-based iconography of the otoliths of all studied species is presented.
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Detection of invasive and alien land planarians as threats to agriculture and ecosystem stability
- Alien land planarians are considered potential threats to European agriculture and ecosystem stability. Severe impact of alien land planarian species in Europe but also worldwide was reported including depletion of local and native soil invertebrates and possible detrimental changes at the ecosystem level. Given the increasing number of studies reporting non-native and potentially invasive species of geoplanid planarians, further action in first response related to worldwide plant trade is called for. To date, the only flatworm on the list of “Invasive Alien Species of European Union Concern” is the New Zealand flatworm Arthurdendyus triangulatus. To help authorities detect and prevent introduction of the New Zealand flatworm, we designed an experiment in order to develop a species-specific barcoding protocol to check possible contamination by A. triangulatus of containerised flowerpots, identified as the most probable source of its co-introduction to non-native region. Based on our results, specific behavior of A. triangulatus staying restricted to the surface and upper layer of the flowerpot determines accessibility of DNA in the soil. Therefore, water-based eDNA methodology combined with a newly established qPCR protocol is preferred as it provides a sensitive approach for detection of A. triangulatus in the flowerpots. Further testing is needed to determine sensitivity of the persistence of eDNA following the flatworm’s removal, to estimate the risk of false positives. The newly designed barcoding protocols provide species-specific diagnosis of one invasive and three non-native land planarians currently being assessed for their invasion risks. However, the species-specificity of the developed barcoding protocols might need to be re-evaluated in case of introduction of new planarian species, and in view of apparent misidentifications regarding published genetic resources. Instead, general protocols requiring genetic sequence analyses would offer a more robust approach to assess species diversity of introduced and potentially invasive land planarians.
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Parasitic monogenean flatworms as tags for invasive aquatic vertebrates in africa, using mitochondrial markers and historical collections
- Reasons why introduced alien species are major risks to biodiversity include parasite co-introduction and lateral transfer to local hosts, but this parasitological impact is understudied. The origins and identities of introduced organisms are often unknown, including those of their parasite fauna. Recent species monitoring only provides partial answers for want of baseline data: especially in the Global South and in sub-Saharan Africa in particular, where native parasite biodiversity is poorly known. We studied introduced vertebrates (cichlids, sardines, frogs) in Central and Southern African inland waters, and parasitic flatworms (monogeneans) infecting them. Given their obligate one-host lifestyle, these parasites are thought to be more easily co-introduced with their hosts, and to be used as “tags” for the origin and introduction pathway of host populations. Parasites were isolated from hosts sampled from historical collections and in recent fieldwork. Monogenean parasites were morphologically identified to species level, and characterised using nuclear and mitochondrial markers. Using historical fish collections to reconstruct pre-introduction baselines for cichlid parasite communities, we distinguished between native and co-introduced parasite species, and detected parasite transmission to native cichlids. Monogeneans helped identify origins and introduction pathways of invasive sardines. For the notoriously invasive Nile tilapia and African clawed frog, these parasites provided a higher resolution than host genetics. This a proof-of-concept of biodiversity infrastructure and parasites as information sources for invasion biology. Nevertheless, a review of the state-of-the-art of parasitological research on Nile tilapia, an invasive f ish of global economic and ecological importance, shows that work on its parasites mostly overlooks their indicator potential. We recommend more scientific consideration to the parasites of invasive species, using a more integrative approach than is currently often taken.
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Exploring co-invasion dynamics: parasitic interactions in the wake of Nile perch invasion in Lake Victoria and its impact on the parasite fauna of haplochromine cichlids
- Biological invasions represent a significant threat to global biodiversity, impacting ecosystems and altering ecological dynamics. The introduction of the Nile perch (Lates niloticus) into Lake Victoria (East Africa), has led to ecological transformations, influencing the native fish communities. While much attention has been devoted to studying the ecological impacts of the Nile perch invasion on the native fish fauna and socio-economic consequences, little is known about the co-introduction dynamics of its potentially co-invasive parasites, as well as the impact on the gill macroparasite fauna of the native fishes impacted by the invasion (e.g. haplochromine cichlids). To investigate the co-introduction dynamics, we assessed the genetic and morphological diversity of Dolicirroplectanum lacustre, the only flatworm (Monogenea) parasite that infects lates perches across Africa. We found that D. lacustre was co-introduced with L. niloticus. In Lake Victoria, we found a reduction in the genetic and morphological diversity of D. lacustre compared with its native range, indicating a founder effect. To examine the broader ecological consequences of Nile perch invasion and human-induced eutrophication, we compared gill macroparasite communities of 13 native haplochromine cichlid species before and after these perturbations. We observed a reconfiguration of the host-parasite network that buffers the impacts of perturbations, indicating resilience. However, we observe a decrease in parasite-host range and infection parameters, highlighting the vulnerability of parasite communities to ongoing environmental changes associated with biological invasions. These findings underscore the importance of understanding the intricate dynamics of host-parasite interactions in the context of biological invasions and environmental change. By integrating insights from the invasive species dynamics and ecological perturbations, we provide valuable insights into the challenges and opportunities for conservation efforts to preserve ecosystem health and resilience in the face of global change.
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infraFADA: Upgrading the taxonomic backbone of global freshwater animal biodiversity research infrastructures
- The current Freshwater Animal Diversity Assessment (FADA) comprises an extensive set of global taxa lists for freshwater animal groups. At present, more than 125 thousand described freshwater animal species in more than 11 thousand genera have been documented. However, taxonomy is a living scientific discipline, where new taxa are continuously being described, and existing taxa are being placed in new taxonomic positions. Therefore, after a period of relative inactivity, the BELSPO (Belgian Science Policy) project “infraFADA” (2023-2026) re-establishes the global FADA consortium of taxonomic experts, so that all taxa lists will be brought up to date, both technically and in terms of content. infraFADA will develop a living, updated, and global FADA database, fully in open access and according to the FAIR principles. The infraFADA database is intended for use and consultation by the scientific freshwater community, as well as for interested stakeholders, for example, freshwater ecosystem managers, biodiversity conservationists, and others. Most importantly, FADA will also serve as a taxonomic backbone for other global biodiversity data infrastructures, such as the Catalogue of Life (CoL), the Global Biodiversity Information Facility (GBIF), the Freshwater Information Platform (FIP), and others. As such, FADA will provide a digital and living heritage of freshwater data, building bridges between science and society and helping to sustainably maintain freshwater resources.
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New lizard from the Early Eocene Vastan Lignite mine of India
- The lower Eocene (Ypresian) Cambay Formation at Vastan Lignite Mine in Gujarat, western India, has yielded a rich vertebrate assemblage including the earliest modern mammals and oldest birds of the Indian subcontinent. Among the herpetological faunas, snakes, lizards and amphibians are abundant, but, strangely, lizards are only represented by agamids. Here we describe the agamid assemblage based on numerous, diverse and well-preserved dentaries, premaxillaries, and maxillaries. At least four taxa are present at Vastan. Vastanagama susanae is characterized by dentaries with a large symphyseal facet, three anterior pleurodont teeth followed by acrodont teeth presenting a main cusp bordered by two lateral crests; the teeth increase in size posteriorly toward the coronoid process. Tinosaurus indicus exhibits a subdental ridge between the tooth row and the Meckelian canal, pleurodont symphyseal teeth including one that can be caniniform, and acrodont and tricuspid posterior teeth with poorly differentiated lateral cusps. Two other taxa represent two new genera and species. The first taxon presents multicuspid acrodont teeth with the main cusp surrounded by two or three progressively smaller lateral cusps. The second taxon presents pleurodont anterior teeth followed by a few acrodont teeth and ending with three or four subacrodont teeth near the coronoid process. Our results confirm that Agamidae (assigned to the Acrodonta) is the only lizard group present at Vastan, whereas many other groups are already present in the Early Eocene on the other continents. Agamidae is considered to have had a Gondwanan origin, with 52 genera and 420 species of extant agamids known from Asia, Australia, Africa and a few from Southern Europe. The oldest occurrence of formally recognized Acrodonta is found in the Jurassic of India. Other fossil agamids are known in the Upper Paleocene of Kazakhstan, Paleocene and Eocene of China, Early Eocene of Europe, Eocene of North America, and Middle Eocene of Pakistan. The diversity of the agamids in India and the absence of other lizard groups at Vastan tentatively support the Out-of-India hypothesis for agamids.
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New bats (Chiroptera) from the Earliest Oligocene Boutersem-TGV locality in Belgium document the earliest occurence of Myotis
- Early Oligocene mammals from Europe are not well known. In Belgium this interval (reference level MP 21) is represented by four coeval localities, Boutersem, Boutersem-TGV, Hoogbutsel and Hoeleden. Included in a vertebrate assemblage of 20+ mammalian genera, one bat, Quinetia misonnei, has been previously described from Hoogbutsel, based on four lower dentitions. Twenty new specimens of Quinetia were recently recovered from Boutersem-TGV including six upper molars, a humerus, and thirteen lower dentitions. These new specimens confirm that Quinetia is a plecotine vespertilionid and consequently represents the earliest known occurrence of this tribe. Additionally, twenty five other dental specimens document the presence of a larger vespertilionid from Boutersem-TGV. These specimens are assigned to Myotis based on the primitive 3.1.3.3 dental formula, the presence of a single-rooted p3, myotodont lower molars, a relatively high crowned lower canine with well-developed mesial and distolingual shelves, M1 and M2 lacking both paraconules and metalophs, protofossa of M1 and M2 open posteriorly, and M3 being relatively short. The Boutersem-TGV Myotis specimens represent the earliest known record of this extant genus. Only some isolated potential myotine teeth from Le Batut (MP 19) in France are older but these teeth differ from Myotis in having upper molars with a paraloph and a protofossa closed posteriorly, both features more typical of the enigmatic “Leuconoe”. Myotodont species, such as “L”. salodorensis from Oensingen (MP 25) in Switzerland and “L”. lavocati from Le Garouillas (MP 25-28) in France, both share features of upper teeth that distinguish them from Myotis. Younger still are three Myotis species from Herrlingen 8-9 (MP 29) in Germany. Compared to the Boutersem-TGV Myotis, M. minor is much smaller with a relatively smaller, shorter and more delicate p4, M. intermedius is somewhat smaller in molar dimensions but with a substantially smaller and shorter p4, while M. major has larger m1-2, similar sized m3, smaller p4, more robust M1 and a more constricted P4 lingual shelf. The origin of Myotis appears to be at least as old as the earliest Oligocene.
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Diversity of archaeonycterid bats in the Early Eocene of Europe
- Chiroptera is one of the few modern mammal orders for which no fossil record has been associated with the Paleocene-Eocene Thermal Maximum. Despite intensive collecting efforts, the earliest remains of bats are still elusive. Archaeonycteris trigonodon from the early Middle Eocene of Messel Formation (MP11) in Germany along with Icaronycteris index and Onychonycteris finneyi, both from the late Early Eocene Green River Formation (Wa7) in Wyoming, have been recognized as representing the most primitive bats based on skeleton morphology. Very few dental features of any of these taxa have been studied in detail because upper and lower dentitions are in occlusion. Nearly one century after its initial description it has become possible to digitally reconstruct the teeth of A. trigonodon using micro-CT scanning technology. This permits characterization of the complete dentition of A. trigonodon and for the first time enables dental comparisons with A. brailloni from the middle Early Eocene of Avenay (MP8+9) in France. The early Early Eocene French locality of Meudon (?MP8+9) has also yielded a few isolated bat teeth that have never been formally described. M1 is distinctly smaller than M2, both have a deep ectoflexus but M1 is more asymmetric than M2. The centrocrista does not extend far toward the labial border and both have a complete lingual cingulum and no paraconule. Lower molars are relatively wide, especially the trigonid of m2. The entoconid of m1 is distinct and individualized whereas it is more reduced and in line with the hypoconulid on m2 and m3. The new taxon from Meudon is similar in size to Archaeonycteris? praecursor from the early Early Eocene of Silveiriha (MP7) in Portugal but differs from that taxon in having lower molars with a relatively longer trigonid and shorter postcristid. These results indicate that the diversity of archaeonycterid bats is higher than previously recognized and that diversification of this lineage began early in the Eocene.
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Sédimentologie des formations de Marteau, du Bois d'Ausse et de la partie inférieure de la Formation d'Acoz (Dévonien inférieur) dans l'Est de la Belgique, au bord nord du Massif de Stavelot
- Deze samenvatting is niet beschikbaar in het Nederlands. Résumé Les Formations de Marteau et du Bois d'Ausse et la partie inférieure de la Formation d'Acoz (Dévonien inférieur) qui affleurent au nord du Massif de Stavelot, dans l'Est de la Belgique, font l'objet d'une étude sédimentologique et pétrographique détaillée et bien documentée. Les observations de terrain reposent sur les coupes de la Helle et de la Gileppe qui ont été décrites banc par banc. Les caractères lithologiques, complétés par un inventaire exhaustif des structures sédimentaires et par le contenu pétrographique, ont permis de dégager les grands traits de l'évolution sédimentaire et de reconstituer les paléoenvironnements. Dans la Formation de Marteau, on observe le passage d'une sédimentation grossière fluviatile, d'abord peu structurée (rivière en tresses), à une plaine alluviale limitée, ensuite à une plaine alluviale large mais plus côtière et soumise à des influences intertidales (ou estuairiennes). Avec la Formation du Bois d'Ausse, la sédimentation littorale devient presque exclusivement gréseuse, traduisant des apports fluviatiles. On observe ensuite le retour temporaire à une plaine alluviale côtière, soumise à des influences intertidales et enfin à un milieu de type barrière de plage à apports fluviatiles. On atteint ici le maximum transgressif de la mer dévonienne pour la tranche temps et la région étudiée. Le retour à une sédimentation exclusivement continentale s'opère rapidement, marquée par le développement des dépôts rouges de la Formation d'Acoz. Abstract The Lower Devonian Marteau and Bois d'Ausse Formations and the lowermost part of the Acoz Formation outcropping north of the Stavelot Massif in Eastern Belgium are the subject of detailed and well documented sedimentological and petrographical investigations. Continuous sections outcropping in the Helle and Gileppe valleys have been described bed by bed. Lithological characters, sedimentary structures and petrographical content are the basis for understanding the sedimentary evolution and paleoenvironments. In the lower part of the Marteau Formation, coarse-grained siliciclastic deposits are indicative of a braided-river system, evolving towards an alluvial plain of limited extent. Sediments from the upper part of the Marteau Formation reflect a more coastal alluvial plain setting, affected by intertidal influences. The littoral environment is obvious in the lower part of the Bois d'Ausse Formation with a sandy sedimentation resulting mainly from fluvial influx. Temporarily, a coastal alluvial plain develops, attested by intertidal influences. Barrier-beach conditions with fluvial influx characterize the upper part of the Bois d'Ausse Formation. It corresponds to the transgressive maximum for the Lower Devonian sea in the studied area. The return to a continental setting is rapid with the development of the red-coloured sediments which characterize the Acoz Formation.
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Le sondage de Focant : lithostratigraphie et implications structurales
- The Focant borehole (185W 407) is located in the Famenne depression, at the southern border of the Dinant Synclinorium. With a depth of 3208 m, this borehole intersects the Famenne Formation (Famennian), the Matagne, Neuville, Grands Breux, Moulin Lienaux and Nismes Formations (Frasnian) and terminates in the Fromelennes Formation (Givetian). The present paper deals with the lithostratigraphy of these formations, their lateral variations and the tectonic structure of the section traversed by the borehole. Four tectonic units can be distinguished: an upper unit consisting of the inverted limb of a complex overturned north facing syncline, cut by numerous reverse south dipping faults; a second unit showing the superposition of tight overturned folds cut by south dipping faults; a third unit consisting of a succession of more gentle north facing anticlines and synclines and a fourth unit made up of a normal succession gently dipping to the south. These observations lead to a new interpretation of the Focant seismic section. Résumé Le sondage de Focant (185W 407) a été implanté dans la dépression de la Famenne, au bord sud du Synclinoriurn de Dinant. Profond de 3208 m, il recoupe à plusieurs reprises les Formations de la Famenne (Famennien), de Matagne, de Neuville, des Grands Breux, du Moulin Lienaux et de Nismes (Frasnien) et se termine dans la Formation de Fromelennes (Givetien). Le présent travail s'intéresse à la lithostratigraphie de ces formations, à leurs variations latérales et à la structure tectonique de la zone traversée par l'ouvrage. Quatres unités tectoniques peuvent être distinguées: une unité supérieure constituée par le flanc inverse d'un synclinal complexe à vergence nord, découpé par un grand nombre de failles inverses à pendage sud; une deuxième unité caractérisée par une superposition de plis fortement déversés et pincés, faillés par des accidents à pente sud; une troisième unité montrant une succession d'anticlinaux et de synclinaux plus ouverts, déversés vers le nord et une quatrième unité constituée d'une série normale à pendage sud modéré. Cette succession d'unités tectoniques permet de jeter un regard nouveau sur la section sismique recoupée par le sondage de Focant. Samenvatting De boring van Focant (l85W-407) is uitgevoerd in de depressie van de Famenne, aan de zuidrand van het Synclinoriurn van Dinant. In deze 3208 m diepe boring worden verschillende keren de Formaties van de Famenne (Famenniaan), Matagne, Neuville, Grands Breux, Moulin Liénaux en Nismes (Frasniaan) aangetroffen. Op einddiepte bevindt de boring zich in de Formatie van Fromelennes (Givetiaan). Dit werk behandelt de lithostratigrafie van deze formaties, de laterale variaties en de tektonische structuur van de doorboorde zone. Vier tektonische eenheden kunnen onderscheiden worden: de bovenste bestaande uit de noordwaarts overhellende flank van een complexe syncline, doortrokken met een groot aantal opschuivingsbreuken met zuidwaartse helling; een tweede eenheid gekenmerkt door een superpositie van sterk overhellende en verknepen plooien met zuidwaarts hellende breuken; een derde eenheid bestaande uit een opeenvolging van meer open anticlines en synclines, noordwaarts overhellend en een vierde eenheid gevormd door een normale reeks met een matige zuidwaartse helling. Deze opeenvolging van tektonische eenheden laat toe nieuwe interpretaties te maken van het seismisch profiel van Focant.
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Les formations du Frasnien de la Belgique
- This memoir on the Frasnian formations of Belgium is the result of meetings and field trips of the National Subcommission on Devonian Stratigraphy. It was prepared in collaboration with geologists involved in the new mapping program of Wallonia at scale 1/25 000. Seventeen formations are described. Six of them (Aisemont, Barvaux, Bovesse, Franc-Waret, Matagne en Rhisnes) are weIl known from literature. The eleven others (Grands Breux, Huccorgne, Lambermont, Lustin, Moulin Liénaux, Neuville, Nismes, Philippeville, Pont de la Folle, Presles and Valisettes) were introduced during the last twenty five years. AIl these formations are revised and presented in files giving a brief historical account, location of the reference sections, lithology, limits and thickness at the stratotype or the reference sections, lateral variations, ages and eventual uses. Furthermore, each formation is documented by the location of the outcrops on a portion of the relevant topographic map (scale 1/10000) and by a cross-section or a stratigraphic log of the stratotype or other reference sections. Lastly, the tables in the opening section provide information on the historical subdivisions of the Frasnian in Belgium, the stratigraphic correlations between the Frasnian formations from different structural units recognized in this work and the stratigraphic distribution of the taxa of the fossil groups cited in the text. Résumé Ce mémoire consacré aux formations frasniennes de la Belgique est le fruit de réunions en salle et de terrain de la Sous-Commission nationale de Stratigraphie du Dévonien et s'intègre dans le cadre du programme de renouvellement des cartes géologiques de Wallonie à 1/25000. Il rassemble les descriptions de dix-sept formations: certaines (Aisemont, Barvaux, Bovesse, Franc-Waret, Matagne, Rhisnes) sont connues de très longue date dans la littérature; les autres (Grands Breux, Huccorgne, Lambermont, Lustin, Moulin Liénaux, Neuville, Nismes, Philippeville, Pont de la Folle, Presles, Valisettes) ont été introduites au cours des vingt-cinq dernières années. Toutes ces formations ont été revues dans le cadre de ce travail et font l' objet d'une fiche détaillée comprenant un bref historique, la localisation des sites de référence, la lithologie, les limites et l'épaisseur dans le stratotype ou les sites de référence, les variations latérales, l'âge et les usages éventuels. En outre, chaque formation est documentée par un extrait de carte topographique à 1/10 000 localisant les affleurements cités et par une coupe ou une colonne lithologique du stratotype et d'autres sites de référence. Enfin, des tableaux placés au début du mémoire illustrent l'historique des subdivisions du Frasnien en Belgique, les corrélations stratigraphiques entre les formations frasniennes reconnues dans les différentes unités structurales utilisées dans le présent travail et la distribution stratigraphique des groupes fossiles cités. Samenvatting Deze verhandeling over de Frasniaan formaties van België is het resultaat van besprekingen en terreinexcursies van de Nationale Subcommissie voor de Stratigrafie van het Devoon en kadert in het programma voor de hernieuwing van de geologische kaarten van Wallonië (schaal 1/25000). ln dit werk worden 17 formaties beschreven: de namen van sommige formaties (Aisemont, Barvaux, Bovesse, Franc-Waret, Matagne en Rhisnes) zijn reeds lang bekend uit de literatuur; de andere formaties (Grands Breux, Huccorgne, Lambermont, Lustin, Moulin Liénaux, Neuville, Nismes, Philippeville, Pont de la Folle, Presles, Valisettes) werden in de loop van de laatste vijfentwintig jaar ingevoerd. ln het kader van dit werk werden al deze formaties herzien en voor ieder van hen worden volgende gegevens verstrekt: een bondige historiek, lokalisatie van de referentieontsluitingen, de lithologie, de grenzen en de dikte in het stratotype of in andere referentieprofielen, de laterale variaties, de ouderdom en het eventueel gebruik, uittreksel van de topographische kaart op 1/10 000 met de besproken ontsluitingen, doorsnede of lithologische kolom van het stratotype of andere referentiesecties. Een reeks tabellen in het begin van de verhandeling geven een historisch overzicht van de onderverdelingen van het Frasniaan van België, de stratigrafische correlaties tussen de Frasniaan formaties in de verschillende structurele eenheden gebruikt in dit werk en de stratigrafische verbreiding van de taxa van de vermelde fossielgroepen.
