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Les lézard Iguania (Pleurodonta et Acrodonta) de l’Eocène inférieur (MP7) de Dormaal, Belgique
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Depuis quelques années, les lézards de l’Eocène basal de Dormaal (niveau-repère MP7), Belgique sont en cours de révision. Après le varanidé Saniwa orsmaelensis et les geckos, ce sont les lézards Iguania qui viennent de faire l’objet d’une étude approfondie. Ce groupe est représenté d’une part par les Acrodonta (incluant les agames et les caméléons), actuellement plutôt distribués dans l’Ancien Monde, et d’autre part par les Pleurodonta (les iguanes), principalement distribués dans le Nouveau Monde. Mais dans nos régions, ces deux groupes de lézards cohabitaient de l’Eocène basal, durant le Maximum Thermique Paléocène-Eocène (PETM), climat le plus chaud des 66 derniers millions d’années, jusqu’à la fin de l’Eocène inférieur (MP10, Prémontré, France). Aujourd’hui cette co-occurrence ne se retrouve plus qu’à Madagascar. Un maxillaire complet de l’agame Tinosaurus europeocaenus, le plus vieil agame européen, donne de nombreux caractères diagnostiques de cette espèce et permet de le rapprocher du genre actuel Leiolepis. Les différences avec Tinosaurus indicus de l’Inde, T. doumuensis de Chine et Tinosaurus sp. d’Amérique du Nord sont aussi discutées. Pour les pleurodontes, à côté du lézard bien connu Geiseltaliellus, un nouveau genre, Bifurcodentodon, a pu être identifié sur base d’un maxillaire présentant une morphologie dentaire toute particulière. En effet, la traditionnelle cuspide centrale des dents est dédoublée indiquant probablement un régime alimentaire spécialisé. Cette spécialisation pourrait avoir causé la perte de ce taxon en raison de la compétition avec les espèces plus généralistes et plus adaptatives faces au changement climatique du Paléogène. Financements Ce travail fut possible grâce au financement SYNTHESYS BE-TAF-8234 de la Commission Européenne (A. Č .), à la bourse 1/0191/21 de l’Agence des Bourses Scientifiques du Ministère de l’Education de Slovaquie et de l’Académie des Sciences de Slovaquie (A. Č .) et au projet Belspo BRAIN BR/121/A3/PALEURAFRICA (T. S.) du Ministère de la Politique Scientifique Belge.
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Dormaal lizards in Belgium – a rare window into the earliest Eocene ‘greenhouse world’
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During the Eocene, world climate experienced rapid and intense global warming, reaching a peak during the Palaeocene–Eocene Thermal Maximum (PETM), 56 my ago. The warmest global climate of the past 66 my occurred during the early Eocene epoch (about 56 to 48 mya) when megathermal floral elements, including palms, reached Antarctica. The increase in temperatures led to a rise in sea level, turning Europe into an archipelago. Data regarding the early Eocene herpetofaunas are scant, but the locality of Dormaal in Belgium represents one of the rare exceptions. The lizards consist of gekkotans, acrodontan and pleurodontan iguanians, anguimorphs such as glyptosaurines and the varanid Saniwa. These groups are believed to be thermophilic, and their appearance in this high latitude locality indicates that the tropics were expanded during this time. Some of these records also represent first appearances of these clades in Europe. Among them, a new iguanian taxon is represented by a unique tooth morphology – the teeth are bifurcated – indicating a specialization on trophic resources. However, because terrestrial ecosystems changed substantially during the Palaeogene, this might have caused higher extinction risk relative to generalists (e.g., the iguanian Geiseltaliellus). Understanding this geological epoch is relevant for present global climate change, including sea level rise, as well as the expansion of distribution of thermophilic taxa, including parasites that cause serious infectious diseases such as malaria.
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RBINS Staff Publications 2023
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Antarctic micrometeorites as a resource to complement the current Solar System inventory: the case of 16O-poor cumulate porphyritic cosmic spherules
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Controls on rare earth element dynamics during low- and high-temperature fluid-rock interactions in carbonatites
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RBINS Staff Publications 2023
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Radiogenic and stable Sr isotope geochemistry of regolith hosted REE deposits: a preliminary report
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RBINS Staff Publications 2023
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Investigating critical metals Ge and Ga in complex sulphide mineral assemblages using LIBS mapping
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Mineralogical and geochemical insights of Fe-Ti-P-REE mineralization in alkaline igneous complexes: example from the Kodal deposit, Oslo Rift, Norway
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Geochemistry of the Larvik Plutonic Complex and its implications for the genesis of its Fe-Ti-P-REE mineralization.
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The amazing evolutionary diversity of a taxon: Genome sizes of twenty Antarctic amphipod species
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Polar ecosystems feature among the last pristine areas of planet Earth, but also among the fastest changing due to global change. The long isolation history of the Southern Ocean has led to high levels of endemism, resulting in a hotspot of biodiversity for many taxa, including crustaceans (Malacostraca). Genomes represent the blueprint of this long evolution. Geographic isolation in combination with harsh and challenging sampling conditions, has left considerable biological knowledge gaps in the Southern Ocean. Closing these knowledge gaps is challenging for Antarctic amphipods because their genome sizes are highly variable and they are hard to sample. Genome size of amphipods are widely varying, ranging from 0.68 to 64.62 pg with an average of 12.85 pg (± 4.46 pg). Unfortunately, information on the genome size of amphipods remains limited, especially from polar regions. Just 65 records of amphipod genome sizes are listed in the Animal Genome Size Database, of which 17 marine species. To close the knowledge gap, I used flow cytometry to estimate the genome size of 32 Antarctic amphipod species. I successfully estimated genome sizes for 20 species, ranging from 0.45 pg to 57.28 pg (> 120-fold difference). Preliminary analyses do not show any significant correlation between depth and genome size or body size and genome size. The results provide a valuable addition to the inventory of the genome size of amphipods, especially from extreme environments.
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Cryptic Diversity, Phylogeography and Genetic Connectivity of Abyssorchomene distinctus (Pacific Ocean and SE Indian Ridge)
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Polymetallic nodule mining is a growing commercial interest over the past three decades. It is critical to accurately estimate biodiversity before any minerals are exploited in the Clarion-Clipperton Zone (CCZ) in the Northeast Pacific Ocean. Scavenging amphipods are a large group in the abyssal biota and play an important role in the nutrient cycling system. This study uses both mitochondrial (COI) and nuclear (28S rRNA) DNA markers to investigate genetic diversity and connectivity in Abyssorchomene distinctus (Lysianassoidea – Uristidae) (Birstein & Vinogradov, 1960). The genetic sequences of 113 sampled individuals of Abyssorchomene distinctus, which originated from the CCZ, the Discol Experimental Area (DEA), the Atacama Trench and the Southeast Indian Ridge, revealed the absence of cryptic diversity for A. distinctus on a global scale. The findings contrasted with those for other closely related scavenging amphipods, which revealed the presence of cryptic species. Population genetics analyses calculated a low haplotype diversity (Hd) within the A. distinctus population across the Pacific Ocean, while a high Hd was found in the Indian Ocean populations. This is the first study to date providing preliminary indications of a possible genetic connectivity of the scavenging amphipod species Abyssorchomene distinctus between the CCZ and DEA, being geographically separated by a vast distance of 5,000 km. Shared haplotypes were also found between the CCZ, DEA, Atacama Trench and the Southeast Indian Ridge in the COI mitochondrial DNA dataset , which was congruent with results from previous studies on other scavenging amphipods.
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RBINS Staff Publications 2023