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Ewin T.A.M.,Natural History Museum in London | Thuy B.,Natural History Museum Luxembourg
Journal of Paleontology | Year: 2017

Three new ophiuran species, Enakomusium whymanae n. Sp., Aspidophiura? seren n. Sp., and Ophiotitanos smithi n. Sp., and an unnamed specimen assignable to the genus Dermocoma are described from the Callovian to Oxfordian Oxford Clay Formation of Great Britain. These determinations are based on new finds and a critical reassessment of historic specimens. The Oxford Clay ophiuroids represent two loose assemblages, one from the middle Callovian Peterborough Member and the other from the lower Oxfordian Weymouth Member. Both assemblages accord well with coeval midshelf mud bottom ophiuroid communities in terms of taxonomic composition and relative abundance of taxa. The British Oxford Clay ophiuroids are particularly significant as they are one of the rare instances where multiple species are represented, almost exclusively, by exceptionally preserved articulated skeletons. This provides an important window into the understanding of mid-Upper Jurassic ophiuroid paleobiology. Copyright © 2017, The Paleontological SocietyÂ.

Thuy B.,Natural History Museum Luxembourg | Hagdorn H.,Muschelkalkmuseum Ingelfingen | Gale A.S.,University of Portsmouth
Geology | Year: 2017

Echinoderms are among the marine invertebrates that underwent the most severe losses at the end-Permian extinction. The prevailing paradigm claims an extreme bottleneck with only very few, if not single, holdovers ("hangovers" herein) sparking the post-Paleozoic radiation. Here we identify previously overlooked Triassic echinoids, ophiuroids, and asteroids as unambiguous members of Paleozoic stem groups. These echinoderm hangovers occurred almost worldwide and had spread into a wide range of paleoenvironments by the Late Triassic. Our discovery challenges fundamentals of echinoderm evolution with respect to end-Permian survival and sheds new light on the early evolution of the modern clades, in particular on Triassic ghost lineages (i.e., inferred but undocumented fossil record) of the crown-group look-alikes of the Paleozoic hangovers. © 2017 Geological Society of America.

Habel J.C.,Natural History Museum Luxembourg | Husemann M.,Baylor University | Schmitt T.,University of Trier | Zachos F.E.,Natural History Museum Vienna | And 4 more authors.
PLoS ONE | Year: 2012

The immense biodiversity of the Atlas Mountains in North Africa might be the result of high rates of microallopatry caused by mountain barriers surpassing 4000 meters leading to patchy habitat distributions. We test the influence of geographic structures on the phylogenetic patterns among Buthus scorpions using mtDNA sequences. We sampled 91 individuals of the genus Buthus from 51 locations scattered around the Atlas Mountains (Antiatlas, High Atlas, Middle Atlas and Jebel Sahro). We sequenced 452 bp of the Cytochrome Oxidase I gene which proved to be highly variable within and among Buthus species. Our phylogenetic analysis yielded 12 distinct genetic groups one of which comprised three subgroups mostly in accordance with the orographic structure of the mountain systems. Main clades overlap with each other, while subclades are distributed parapatrically. Geographic structures likely acted as long-term barriers among populations causing restriction of gene flow and allowing for strong genetic differentiation. Thus, genetic structure and geographical distribution of genetic (sub)clusters follow the classical theory of allopatric differentiation where distinct groups evolve without range overlap until reproductive isolation and ecological differentiation has built up. Philopatry and low dispersal ability of Buthus scorpions are the likely causes for the observed strong genetic differentiation at this small geographic scale. © 2012 Habel et al.

Hess H.,Naturhistorisches Museum Basel | Thuy B.,Natural History Museum Luxembourg
Swiss Journal of Palaeontology | Year: 2016

Comatulid feather stars are rare fossils in the Early Jurassic, providing only patchy insights into the early evolution of the group. Here, we describe new finds of comatulids from the late Pliensbachian to late Toarcian of Feuguerolles, Calvados, France. They include new species belonging to four superfamilies. The dominant genus is Palaeocomaster, with P. structus n. sp. represented by centrodorsals. For Palaeocomaster, the family Palaeocomasteridae n. fam. is proposed; it is placed in the Superfamily Comatuloidea. Solanocrinites is represented by S. jagti n. sp. The new taxa Andymetra toarcensis n. sp. and Spinimetra chesnieri n. g. et n. sp. are Family incertae sedis. The diagnoses of Comatuloidea and Solanocrinitoidea are modified based on the new material. The paracomatulid Singillatimetratruncata n. sp. is represented by a columnal, as is Forcipicrinusnormannicus n. g. et n. sp. tentatively assigned to Pentacrinitina, Family incertae sedis. The material indicates that an important early comatulid radiation took place prior to the Toarcian Oceanic Anoxic Event, creating some basic types of these free-living crinoids. Along with the stratigraphic distribution patterns of the co-occurring stalked crinoids including the isocrinids Pentacrinitescollenoti, Isocrinus (Chladocrinus) basaltiformis, the millericrinid Amaltheocrinusamalthei, and the cyrtocrinids Cotylederma docens, Eudesicrinus mayalis, Praetetracrinusinornatus, Sacariacrinus n. sp. and Tetracrinus n. sp., the new feather star finds suggest that the Toarcian Oceanic Anoxic Event was not of major influence to crinoid diversity. © 2016 Akademie der Naturwissenschaften Schweiz (SCNAT)

Habel J.C.,Natural History Museum Luxembourg | Husemann M.,Baylor University | Schmitt T.,University of Trier | Dapporto L.,Instituto Comprensivo Materna Elementare Media Convenevole da Prato | And 2 more authors.
Journal of Heredity | Year: 2013

Numerous studies addressing the impact of habitat fragmentation on genetic diversity have been performed. In this study, we analyze the effects of a seemingly nonpermeable matrix on the population structure of the forest-dwelling butterfly Pararge aegeria in geographically isolated oases at the northern margin of the Sahara desert using microsatellites, morphological characters, and species distribution modeling. Results from all analyses are mostly congruent and reveal 1) a split between European and North African populations, 2) rather low divergence between populations from the eastern and western part of North Africa (Morocco vs. Tunisia), 3) a lack of differentiation between the oasis and Atlas Mountain populations, 4) as well as among the oasis populations, and 5) no reduction of genetic variability in oasis populations. However, one exception to this general trend resulted from the analyses of wing shape; wings of butterflies from oases are more elongated compared with those from the other habitats. This pattern of phenotypic divergence may suggest a recent colonization of the oasis habitats by individuals, which might be accompanied by a rather dispersive behavior. Species distribution modeling suggests a fairly recent reexpansion of the species' climatic niche starting in the Holocene at about 6000 before present. The combined results indicate a rather recent colonization of the oases by highly mobile individuals from genetically diverse founder populations. The colonization was likely followed by the expansion and persistence of these founder populations under relatively stable environmental conditions. This, together with low rates of gene flow, likely prevented differentiation of populations via drift and led to the maintenance of high genetic diversity. © The American Genetic Association. 2012. All rights reserved.

Augenstein B.,Natural History Museum Luxembourg | Ulrich W.,Nicolaus Copernicus University | Habel J.C.,Natural History Museum Luxembourg
Basic and Applied Ecology | Year: 2012

Oligotrophic calcareous grasslands are among the most species-rich habitats in temperate Europe. Land use changes caused a severe decline of these species-rich grasslands over the last decades. Today, these ecosystems exist as highly isolated and small remnants being threatened by abandonment, afforestation and the transformation into agricultural land. Local conservation activities caused changes in habitat structures within such oligotrophic calcareous grasslands and their often isolated character may have led to stochastic species extinctions due to population fluctuations. In this study we focus on potential changes of grassland biota over the past decades. We analyse retrospective species inventories (14 for carabid beetles and 7 for butterflies) from calcareous grasslands located in western Germany with adjoining parts of Luxembourg over a period from 1972 to 2011. Our data indicate two distinct temporal cohorts (past versus present) that differ strongly in the composition and structure of carabid beetles and butterfly communities. Patterns of species co-occurrences tended to be segregated in the past communities while the co-occurrences in recent communities were either random or aggregated. β-Diversity increased with time. Our results indicate a temporal shift from past communities dominated by species interactions towards recent neutral assemblages. These changes might be caused by diverging conservation management being restricted to local sites. This resulted in a higher diversity of environmental structures combined with a loss of grassland habitats and declining matrix permeability. However, we detected no loss of rare carabid beetles, while butterflies showed severe extinctions of species with specific habitat demands, high endangerment and/or low dispersal behaviour. These trends let us argue that carabid communities mirror local changes in habitat structure (caused by conservation action), while butterflies show additional effects due to environmental stochasticity, local extinctions and a subsequent lack of re-colonization from adjoining populations. © 2012.

Habel J.C.,Natural History Museum Luxembourg | Schmitt T.,University of Trier
Biological Conservation | Year: 2012

In general, species with large ecological amplitudes are equipped with high genetic diversities. In contrast, more specialised species with narrow ecological amplitudes show low levels of genetic diversity. Generalist species are mostly rather marginally affected by recent land-use changes; specialist can be supported by specific conservation measures. We argue that, in the light of Conservation Genetics, species being ecologically intermediate between these two extremes are the most seriously affected ones by recent environmental changes. Such species which formerly occurred in large population networks have to sustain their high level of genetic variability via gene flow. Today, species from the latter group are negatively affected by rapid habitat collapses causing sudden lacks of population interconnectivity. Therefore, species with intermediate habitat demands and originally high genetic diversity might be at highest risk due to inbreeding depressions. © 2011 Elsevier Ltd.

Husemann M.,Baylor University | Schmitt T.,University of Trier | Stathi I.,University of Crete | Habel J.C.,Natural History Museum Luxembourg
Journal of Heredity | Year: 2012

When low dispersal ability of an organism meets geographical barriers, the evolution of inter- and intraspecific differentiation is often facilitated. In the Atlas massif of North Africa, the genus Buthus splits into several species and diverges into numerous genetic lineages, often following the orographic structures of mountain systems. Such high mountain ranges often act as barriers for species with reduced mobility even on small spatial scales. To study the effect of orographic structures on organisms with low dispersal ability, we collected 61 individuals of the scorpion species Buthus elmoutaouakili at 18 locations around the southwestern foothills of the High Atlas and Antiatlas and in the Sousse valley (western Morocco). We analyzed intraspecific differentiation patterns within this geographically restricted area of about 100 × 50 km using 452 bp of the cytochrome oxidase I mitochondrial gene. We detected 5 distinct genetic lineages. In a second analysis, we added 61 previously published sequences from Buthus species from Europe and North Africa. Using a molecular clock approach, we detected old splits (4-5 Ma) separating the samples from 1) the western High Atlas and north of these mountains, 2) the Sousse valley and adjoining mountain areas, and 3) the southwestern Antiatlas. Further differentiation happened in the first 2 geographical groups about 3 M.A. Thus, the divergence time estimates based on a Bayesian approach support the onset of differentiation into these main clades along the Pliocene (5-2.3 Ma) when climatic oscillations started and a constant global cooling preceded the glacial-interglacial cycles of the Pleistocene. Further genetic splits into parapatric groups are detectable for the Sousse valley main group in the early Pleistocene. The climatic oscillations of the Pliocene and early Pleistocene might have caused repeated range shifts, expansions, and retractions leading to repeated vicariance, hereby producing the hierarchical structure of genetic differentiation in B. elmoutaouakili. A taxonomic revision, including morphological and molecular data, is needed to assess the status of each of these Buthus scorpion lineages. © The American Genetic Association. 2012. All rights reserved.

Thuy B.,Natural History Museum Luxembourg | Kutscher M.,Dorfstrasse 10 | Plachno B.J.,Jagiellonian University
Acta Palaeontologica Polonica | Year: 2015

The fossil record of Paleozoic ophiuroids includes a number of forms which share striking similarities with modern relatives in terms of skeletal morphology. These so called modern-type Paleozoic ophiuroids yield an enormous potential for a better understanding of ophiuroid evolution, yet the scarcity of accurate and sufficiently detailed morphological descriptions available to date precludes any further-reaching assessments. Here, we describe an articulated ophiuroid specimen from the Late Tournaisian (early Carboniferous) of Czatkowice quarry, southern Poland, as a new species Aganaster jagiellonicus sp. nov. The good preservation of the specimen allowed for a morphological analysis at a level comparable to recent ophiuroid descriptions. It shows remarkable morphological similarities with extant former ophiolepidids Ophiomusium and Ophiosphalma. The new find thus contributes to a solid basis for future investigations on the position of the modern-type Paleozoic ophiuroid in the phylogeny of the class. © 2015 B. Thuy et al.

Thuy B.,Natural History Museum Luxembourg | Stohr S.,Swedish Museum of Natural History
PLoS ONE | Year: 2016

Ophiuroid systematics is currently in a state of upheaval, with recent molecular estimates fundamentally clashing with traditional, morphology-based classifications. Here, we attempt a long overdue recast of a morphological phylogeny estimate of the Ophiuroidea taking into account latest insights on microstructural features of the arm skeleton. Our final estimate is based on a total of 45 ingroup taxa, including 41 recent species covering the full range of extant ophiuroid higher taxon diversity and 4 fossil species known from exceptionally preserved material, and the Lower Carboniferous Aganaster gregarius as the outgroup. A total of 130 characters were scored directly on specimens. The tree resulting from the Bayesian inference analysis of the full data matrix is reasonably well resolved and well supported, and refutes all previous classifications, with most traditional families discredited as poly- or paraphyletic. In contrast, our tree agrees remarkably well with the latest molecular estimate, thus paving the way towards an integrated new classification of the Ophiuroidea. Among the characters which were qualitatively found to accord best with our tree topology, we selected a list of potential synapomorphies for future formal clade definitions. Furthermore, an analysis with 13 of the ingroup taxa reduced to the lateral arm plate characters produced a tree which was essentially similar to the full dataset tree. This suggests that dissociated lateral arm plates can be analysed in combination with fully known taxa and thus effectively unlocks the extensive record of fossil lateral arm plates for phylogenetic estimates. Finally, the age and position within our tree implies that the ophiuroid crown-group had started to diversify by the Early Triassic. © 2016 Thuy, Stöhr. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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