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The present monograph includes general systematic considerations on the family Epimeriidae, a revision of the genus Epimeria Costa in Hope, 1851 in the Southern Ocean, and a shorter account on putatively related eusiroid taxa occurring in Antarctic and sub-Antarctic seas. The former epimeriid genera Actinacanthus Stebbing, 1888 and Paramphithoe Bruzelius, 1859 are transferred to other families, respectively to the Acanthonotozomellidae Coleman & J.L. Barnard, 1991 and the herein re-established Paramphithoidae G.O. Sars, 1883, so that only Epimeria and Uschakoviella Gurjanova, 1955 are retained within the Epimeriidae Boeck, 1871. The genera Apherusa Walker, 1891 and Halirages Boeck, 1891, which are phylogenetically close to Paramphithoe, are also transferred to the Paramphithoidae. The validity of the suborder Senticaudata Lowry & Myers, 2013, which conflicts with traditional and recent concepts of Eusiroidea Stebbing, 1888, is questioned. Eight subgenera are recognized for Antarctic and sub-Antarctic species of the genus Epimeria: Drakepimeria subgen. nov., Epimeriella K.H. Barnard, 1930, Hoplepimeria subgen. nov., Laevepimeria subgen. nov., Metepimeria Schellenberg, 1931, Pseudepimeria Chevreux, 1912, Subepimeria Bellan-Santini, 1972 and Urepimeria subgen. nov. The type subgenus Epimeria, as currently defined, does not occur in the Southern Ocean. Drakepimeria species are superficially similar to the type species of the genus Epimeria: E. cornigera (Fabricius, 1779), but they are phylogenetically unrelated and substantial morphological differences are obvious at a finer level. Twenty-seven new Antarctic Epimeria species are described herein: Epimeria (Drakepimeria) acanthochelon subgen. et sp. nov., E. (D.) anguloce subgen. et sp. nov., E. (D.) colemani subgen. et sp. nov., E. (D.) corbariae subgen. et sp. nov., E. (D.) cyrano subgen. et sp. nov., E. (D.) havermansiana subgen. et sp. nov., E. (D.) leukhoplites subgen. et sp. nov., E. (D.) loerzae subgen. et sp. nov., E. (D.) pandora subgen. et sp. nov., E. (D.) pyrodrakon subgen. et sp. nov., E. (D.) robertiana subgen. et sp. nov., Epimeria (Epimeriella) atalanta sp. nov., Epimeria (Hoplepimeria) cyphorachis subgen. et sp. nov., E. (H.) gargantua subgen. et sp. nov., E. (H.) linseae subgen. et sp. nov., E. (H.) quasimodo subgen. et sp. nov., E. (H.) xesta subgen. et sp. nov., Epimeria (Laevepimeria) anodon subgen. et sp. nov., E. (L.) cinderella subgen. et sp. nov., Epimeria (Pseudepimeria) amoenitas sp. nov., E. (P.) callista sp. nov., E. (P.) debroyeri sp. nov., E. (P.) kharieis sp. nov., Epimeria (Subepimeria) adeliae sp. nov., E. (S.) iota sp. nov., E. (S.) teres sp. nov. and E. (S.) urvillei sp. nov. The type specimens of E. (D.) macrodonta Walker, 1906, E. (D.) similis Chevreux, 1912, E. (H.) georgiana Schellenberg, 1931 and E. (H.) inermis Walker, 1903 are re-described and illustrated. Besides the monographic treatment of Epimeriidae from the Southern Ocean, a brief overview and identification keys are given for their putative and potential relatives from the same ocean, i.e., the Antarctic and sub-Antarctic members of the following eusiroid families: Acanthonotozomellidae Coleman & J.L. Barnard, 1991, Dikwidae Coleman & J.L. Barnard, 1991, Stilipedidae Holmes, 1908 and Vicmusiidae Just, 1990. This overview revealed the existence of a new large and characteristic species of Alexandrella Chevreux, 1911, A. chione sp. nov. but also shows that the taxonomy of that genus remains poorly known and that several ‘variable widespread eurybathic species’ probably are species complexes. Furthermore, the genera Bathypanoploea Schellenberg, 1939 and Astyroides Birstein & Vinogradova, 1960 are considered to be junior synonyms of Alexandrella. Alexandrella mixta Nicholls, 1938 and A. pulchra Ren in Ren & Huang, 1991 are re-established herein, as valid species. It is pointed out that this insufficient taxonomic knowledge of Antarctic amphipods impedes ecological and biogeographical studies requiring precise identifications. Stacking photography was used for the first time to provide iconographic support in amphipod taxonomy, and proves to be a rapid and efficient illustration method for large tridimensionally geometric species. A combined morphological and molecular approach was used whenever possible for distinguishing Epimeria species, which were often very similar (albeit never truly cryptic) and sometimes exhibited allometric and individual variations. However in several cases, taxa were characterized by morphology only, whenever the specimens available for study were inappropriately fixed or when no sequences could be obtained. A large number of Epimeria species, formerly considered as eurybathic and widely distributed, proved to be complexes of species, with a narrower (overlapping or not) distribution. The distributional range of Antarctic Epimeria is very variable from species to species. Current knowledge indicates that some species from the Scotia Arc and the tip of the Antarctic Peninsula are narrow range endemics, sometimes confined to one island, archipelago, or ridge (South Georgia, South Orkney Islands, Elephant Island or Bruce Ridge); other species have a distribution encompassing a broader region, such as the eastern shelf of the Weddell Sea, or extending from the eastern shelf of the Weddell Sea to Adélie Coast. The most widely distributed species are E. (D.) colemani subgen. et sp. nov., E. (E.) macronyx (Walker, 1906), E. (H.) inermis Walker, 1903 and E. (L.) walkeri (K.H. Barnard, 1930), which have been recorded from the Antarctic Peninsula/South Shetland Islands area to the western Ross Sea. Since restricted distributions are common among Antarctic and sub-Antarctic Epimeria, additional new species might be expected in areas such as the Kerguelen Plateau, eastern Ross Sea, Amundsen Sea and the Bellingshausen Sea or isolated seamounts and ridges, where there are currently no Epimeria recorded. The limited distribution of many Epimeria species of the Southern Ocean is presumably related to the poor dispersal capacity in most species of the genus. Indeed with the exception of the pelagic and semipelagic species of the subgenus Epimeriella, they are heavy strictly benthic organisms without larval stages, and they have no exceptional level of eurybathy for Antarctic amphipods. Therefore, stretches deeper than 1000 m seem to be efficient geographical barriers for many Epimeria species, but other isolating factors (e.g., large stretches poor in epifauna) might also be at play. The existence of endemic shelf species with limited dispersal capacities in the Southern Ocean (like many Epimeria) suggests the existence of multiple ice-free shelf or upper slope refugia during the Pleistocene glaciations within the distributional and bathymetric range of these species. Genera with narrow range endemics like Epimeria would be excellent model taxa for locating hotspots of Antarctic endemism, and thus potentially play a role in proposing meaningful Marine Protected Areas (MPAs) in the Southern Ocean.

Résumé : La fouille récente du gisement alluvial de Kerkhove (Belgique), situé dans la vallée de l’Escaut, à une vingtaine de kilomètres de la frontière française, a permis de mettre au jour 17 locus mésolithiques. D’après les données typochronologiques et les datations absolues, ces locus datent non seulement du Mésolithique ancien, mais aussi du Mésolithique moyen et récent. La première phase d’occupation de la levée alluviale, datée du 11e et 10e millénaire avant le présent (cal BP), a clairement été la plus intensive. Elle correspond à un Mésolithique ancien caractérisé par des assemblages du « groupe de Chinru », dominés par les triangles et les pointes à base retouchée. La deuxième phase d’occupation, celle du Mésolithique moyen, compte trois locus et est caractérisée par de nombreuses lamelles étroites à bord abattu, et des pointes à retouche couvrante d’une part, et par une exploitation de matières premières siliceuses différentes d’autre part. La dernière phase d’occupation date du Mésolithique récent. Elle est représentée par un seul locus qui a livré de nombreux artefacts en grès-quartzite de Wommersom, quelques trapèzes et des lamelles plus régulières. Le principal intérêt du site de Kerkhove est la possibilité d’étudier tous les aspects de l’industrie lithique, mais également l’exploitation des matières premières siliceuses et des autres ressources naturelles dans une large perspective diachronique. En effet, hors vestiges lithiques, des quantités considérables de coquilles de noisettes carbonisées et de restes fauniques ont été récupérées. En plus de la présence d’ossements brûlés, des restes fauniques non brûlés sont également conservés, situation inédite pour le Mésolithique ancien, moyen et récent du nord de la Belgique. Ainsi, les ossements de sanglier et de chevreuil dominent les assemblages du Mésolithique ancien et sont associés à des restes d’animaux à fourrures, tandis que les contextes du Mésolithique moyen livrent des indices fréquents de consommation de poissons sur le site. Mots-clés : Mésolithique ancien, Mésolithique moyen, RMS, Mésolithique récent, faune, poisson, tracéologie lithique, analyse spatiale. Abstract: 17 Mesolithic artefact loci were discovered on an alluvial levee during recent excavations at the wetland site of Kerkhove, located in the Scheldt floodplain at about 20 km from the French border. On typochronological grounds, these artefact loci are mainly dated to the Early Mesolithic, already well known from previous large-scale excavations in the lower Scheldt basin, but also to the lesser known Middle and Late Mesolithic periods. The first occupation phase proved to be the most intense and lasted from the middle of the 11th to the middle of the 10th millennium cal BP, based on a series of 19 14C-dates on single entity charred hazelnut shells. At least 9 different artefact loci belonging to this period were documented, covering either small (< 40 m2) or rather large areas (> 100 m2). The microlith compositions of most of these clusters were dominated by triangles and points with retouched base, corresponding to the regional assemblage type of the « Chinru group ». The second occupation phase, the Middle Mesolithic, was harder to define spatially, due to its location on the western edge of the excavation area and to its partial admixture with Early Mesolithic artefacts at specific locations. Nevertheless, three distinct artefact loci were discovered, characterised by the presence of numerous small backed bladelets combined with occasional points with invasive retouch on the one hand and by a different exploitation of lithic raw material resources on the other hand. Besides these more traditional clusters, several discrete concentrations of armatures were located in the low-density areas to the west of the most important Middle Mesolithic occupation zone. Unfortunately, this Middle Mesolithic occupational phase could not be directly dated by ecofacts associated with the artefact loci. However, two dates on unburnt faunal remains recovered from the colluvial deposits on the slope of the levee, indicate that this Middle Mesolithic occupation could date to as early as the second part of the 10th millennium cal BP, at the very beginning of the Middle Mesolithic period. Finally, the last occupation of the site dates to the Late Mesolithic and is only represented by one artefact locus, that contained regular Wommersom quartzite and flint bladelets associated with a few trapezes. Unfortunately, no absolute dates were obtained for this cluster to corroborate and specify its chronological position. This being said, the Kerkhove site offers the advantage, compared to previously excavated sites, that it allows us to study evolutions in lithic typology, lithic technology, tool-uses and the exploitation of lithic raw materials and other types of natural resources from a multi-period perspective. Indeed, besides lithics, considerable amounts of carbonized hazelnut shells and faunal remains were recovered, the latter consisting not only of heavily burnt bone fragments but also numerous unburnt remains. This particular feature of the site is unprecedented within the Early to Late Mesolithic of northern Belgium and allows us for the first time to reconstruct the subsistence behaviour of the Mesolithic hunter-gatherers of the Scheldt basin. Furthermore, the detailed excavation methodology applied, allows for a high-resolution intra-site analysis including not only the spatially well-defined artefact loci but also the areas in between, characterized by the occurrence of small and a low-density artefact clusters. The most interesting preliminary results consist of the striking differences between the distinct occupations phases of the sites on several levels, from the general layout and spatial organisation, over site-function, raw material procurement to the exploitation of animal and plant resources. These differences are particularly outspoken when comparing the Early and Middle Mesolithic occupation of the site. The Early Mesolithic occupation appears homogeneous and is mainly characterised by the use of Scheldt flint, the systematic presence of carbonised hazelnut shells, the almost systematic presence of hearths in the clusters and the functional organisation of space, that doesn’t show contrasts between the individual clusters. Moreover, medium-sized mammals like wild boar and roe deer dominate these assemblages and they are to a lesser extent accompanied by fur-animals such as pine marten. By contrast, the layout and the general use of space of the Middle Mesolithic occupation seems to diverge completely from this picture. From this time onwards, Wommersom quartzite is imported and the use of the Scheldt flint is largely abandoned in favour of a grey-brown translucent and more fine-grained flint, probably indicating a change in the social territorial boundaries of the groups occupying the site of Kerkhove. Besides this, from a functional point of view, the clusters clearly contrast with one another and seem to form special activity areas, although it remains to be proven whether they are complementary special activity areas from one and the same larger campsite or if they are non-contemporaneous, individually functioning clusters. Furthermore, hearth features and carbonised hazelnut shells are completely absent from these artefact loci. Finally, in addition to the exploitation of wild boar, roe deer, red deer and fur animals, from the Middle Mesolithic onwards, we have indications for the consumption of freshwater fish at the site, in the form of burnt fish remains associated with the aforementioned discrete armature clusters. Keywords: Early Mesolithic, Middle Mesolithic, RMS, Late Mesolithic, faunal remains, fish, microwear-analysis, spatial analysis.