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Evolution of the European mesonychid mammals and theur bearings on the European Paleoecosystems and biostratigraphy
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European mesonychids are represented by few specimens found only in late Paleocene and early Eocene localities. Recent field works in Palette and La Borie (Ypresian of France) resulted in the discovery of new mesonychid specimens. Additionally, our review of the mesonychids housed by European scientific institutions allowed establishing the occurrence of Dissacus in Berru (Thanetian) and Sézanne-Broyes (Ypresian). Only the genera Pachyaena and Dissacus are recognized in Europe. Furthermore, two new Dissacus species can be defined from the Ypresian localities of Palette, Sézanne-Broyes and La Borie. We also identified from three localities several postcranial elements that could be referred to Dissacus. The preliminary study of this postcranial material suggests a cursorial locomotion. As a result of our study, we propose a scheme of evolution comprising three phases for these particular mammals in Europe. (1) The mesonychid Dissacus dispersed into Europe during Thanetian, probably from North America; it survived the PETM event and even possibly experienced a dwarfism during this global warming. (2) The very large mesonychid Pachyaena migrated into Europe shortly after the Paleocene–Eocene boundary, but it seems that it did not coexist with Dissacus: it was restricted to Northern Europe, while Dissacus was possibly present at that time only in southern areas. (3) However, Pachyaena rapidly disappeared from the European environments, while Dissacus dispersed subsequently into Northern Europe. These data support the existence of a faunal turnover in Northern Europe shortly after the PETM event: it has been notably proposed for explaining the disappearance from Europe of the carnivorous oxyaenids and hyaenodont sinopines, and their subsequent replacement by taxa from the southern areas. The persistence of Dissacus in Europe shows that size was not the main selective factor during this dramatic period. Dissacus has evolved endemically during Thanetian and Ypresian in Europe where it reached a very large size, especially in southern France and Spain. Due to its size, dental, and locomotor adaptations, Dissacus was probably the top mammal predator in Europe. It survived in Europe after its disappearance from North America, possibly due to its ecologic position and the lack of competitors. Grant Information This abstract is a contribution to the project BR/121/A3/PALEURAFRICA funded by the Belgian Science Policy Office.
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Evolution of the hypercarnivorous dentition in mammals (Metatheria, Eutheria) and its bearing on the development of tribosphenic molars
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One major innovation of mammals is the tribosphenic molar, characterized by the evolution of a neomorphic upper cusp (¼protocone) and a lower basin (talonid) that occlude and provide shearing and crushing functions. This type of molar is an evolutionarily flexible structure that enabled mammals to achieve complex dental adaptations. Among carnivorous mammals, hypercarnivory is a common trend that evolved several times among therians (marsupials, placentals, and stem relatives). Hypercarnivory involves an important simplification of the carnassial molar pattern from the ancestral tribosphenic molar pattern, with the modification of the triangular tooth crown, and the loss of several cusps and cuspids typical of the tribosphenic molar. These losses confer to the molars of the hypercarnivorous mammals a plesiomorphic /paedomorphic morphology that resembles more the earliest mammaliaforms than the earliest therians. Here, we demonstrate that the modification of the molar morphology is fully explained by a patterning cascade mode of cusp development. Contrary to what was previously proposed, our study concludes that the metaconid (mesiolingual cusp of lower molars, associated with a puncturing function) does not influence cusp development of the talonid (distal crushing heel of lower molars). Moreover, it provides a new example of how heterochronic changes were crucial to the evolution of mammal dentition. To overcome the difficulty of applying behavioral or ecological definitions of diets to fossil animals, we characterize hypercarnivorous dentitions on the basis of the molar morphology and more particularly on the loss or retention of crushing structures, each dentition resulting from adaptations to a distinct ecomorphotype. Despite repeated and convergent evolution of hypercarnivorous forms, hypercarnivory appears as a highly constrained specialization (i.e., “dead end”) that is unlikely to evolve back to omnivorous dentition, especially when the crushing structures are lost.
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RBINS Staff Publications 2017
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Evolution sédimentaire et Ostracodes de la base du Givetien à Resteigne (bord sud du Bassin de Dinant, Belgique)
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Evolutionary history of a dispersal-associated locus across sympatric and allopatric divergent populations of a wing-polymorphic beetle across Atlantic Europe
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Studying the evolutionary history of trait divergence, in particular those related to dispersal capacity, is of major interest for the process of local adaptation and metapopulation dynamics. Here, we reconstruct the evolution of different alleles at the nuclear-encoded mitochondrial NADP+-dependent isocitrate dehydrogenase (mtIdh) locus of the ground beetle Pogonus chalceus that are differentially and repeatedly selected in short- and long-winged populations in response to different hydrological regimes at both allopatric and sympatric scales along the Atlantic European coasts. We sequenced 2788 bp of the mtIdh locus spanning a ~7-kb genome region and compared its variation with that of two supposedly neutral genes. mtIdh sequences show (i) monophyletic clustering of the short-winged associated mtIDH-DE haplotypes within the long-winged associated mtIDH-AB haplotypes, (ii) a more than tenfold lower haplotype diversity associated with the mtIDH-DE alleles compared to the mtIDH-AB alleles and (iii) a high number of fixed nucleotide differences between both mtIDH haplotype clusters. Coalescent simulations suggest that this observed sequence variation in the mtIdh locus is most consistent with a singular origin in a partially isolated subpopulation, followed by a relatively recent spread of the mtIDHDE allele in short-winged populations along the Atlantic coast. These results demonstrate that even traits associated with decreased dispersal capacity can rapidly spread and that reuse of adaptive alleles plays an important
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Evolutionary history of the calcareous sponge Clathrina aurea: genetic connectivity in the Western Atlantic and intriguing occurrence in the Eastern Pacific
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RBINS Staff Publications 2021
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Evolutionary history of the thicket rats (genus Grammomys) mirrors the evolution of African forests since late Miocene
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Aim Grammomys are mostly arboreal rodents occurring in forests, woodlands and thickets throughout sub-Saharan Africa. We investigated whether the divergence events within the genus follow the existing evolutionary scenario for the development of African forests since the late Miocene. Location Sub-Saharan African forests and woodlands. Methods We inferred the molecular phylogeny of Grammomys using Bayesian and maximum likelihood methods and DNA sequences of 351 specimens collected from across the distribution of the genus. We mapped the genetic diversity, estimated the divergence times by a relaxed clock model and compared evolution of the genus with forest history. Results Phylogenetic analysis confirms the monophyly of Grammomys and reveals five main Grammomys lineages with mainly parapatric distributions: (1) the poensis group in Guineo-Congolese forests; (2) the selousi group with a distribution mainly in coastal forests of southern and eastern Africa; (3) the dolichurus group restricted to the easternmost part of South Africa; (4) the macmillani group in the northern part of eastern and Central Africa with one isolated species in Guinean forests; and (5) the surdaster group, widely distributed in eastern Africa south of the equator. Every group contains well supported sublineages suggesting the existence of undescribed species. The earliest split within the genus (groups 1 vs. 2–5) occurred in the late Miocene and coincides with the formation of the Rift Valley which resulted in the east–west division of the initially pan-African forest. The subsequent separation between groups (2 vs. 3–5) also dates to the end of the Miocene and suggests the split between Grammomys from coastal to upland forests in eastern Africa followed by a single dispersal event into western Africa during the Pleistocene. Conclusions The evolutionary history of the genus Grammomys closely reflects the accepted scenario of major historical changes in the distribution of tropical African forests since the late Miocene.
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RBINS Staff Publications 2016
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EVOSHEEP: the makeup of sheep breeds in the ancient Near East
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The EVOSHEEP project combines archaeozoology, geometric morphometrics and genetics to study archaeological sheep assemblages dating from the sixth to the first millennia BC in eastern Africa, the Levant, the Anatolian South Caucasus, the Iranian Plateau and Mesopotamia. The project aims to understand changes in the physical appearance and phenotypic characteristics of sheep and how these related to the appearance of new breeds and the demand for secondary products to supply the textile industry.
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RBINS Staff Publications 2021
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Excavations at Hierakonpolis
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Exceptional cryptic diversity and multiple origins of parthenogenesis in a freshwater ostracod
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RBINS Staff Publications
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Exchange processes and nitrogen cycling on the shelf and continental slope of the Black Sea basin.
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A 3D coupled biogeochemical-hydrodynamical model has been applied to the Black Sea to simulate nitrogen cycling and to estimate the exchange of biogeochemical components at the shelf break and between the continental slope and the deep sea. It was found that biological processes on the northwestern shelf are in approximate balance. Primary production is fueled by river discharge, nitrate input from the open sea at the shelf break, and in situ remineralization. The input of nitrate from the open sea is roughly equivalent to the river nitrate discharge but is half the nitrate export from the shelf toward the open sea. Also, the Black Sea shelf acts throughout the year as a nitrate source for the open sea. The amount of shelf production not remineralized in the euphotic layer is 22.2% and is exported to lower layers (20%) or offshore (2.2%). We estimate that the export of carbon from the shelf to the interior of the basin represents 2.5% of the new production of the open sea. The upper slope adjoining the northwestern shelf is the site of downwelling events responsible for the downward transport to the intermediate layer of the continental slope of biogeochemical components exported from the shelf in the upper layer. The shelf has been found to be an efficient trap for the refractory material discharged by the Danube.
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