Kuppers R.,University of Duisburg - Essen |
Duhrsen U.,University of Duisburg - Essen |
Hansmann M.-L.,Senckenberg Institute
The Lancet Oncology | Year: 2014
In rare instances, two distinct lymphomas concurrently occur in a patient. Such composite lymphomas can be combinations of two non-Hodgkin lymphomas or a combination of a non-Hodgkin lymphoma and a Hodgkin's lymphoma. Composite lymphomas pose a particular diagnostic challenge, and there are currently no agreed standards for treatment. Combined B-cell non-Hodgkin lymphomas are often clonally unrelated. However, in many composite non-Hodgkin lymphomas and Hodgkin's lymphomas, the tumours are clonally related. In most of these instances, the malignant clones developed separately from a common precursor, usually a germinal centre B cell. This finding suggests a scenario in which the common premalignant precursor had acquired shared transforming events, and the two distinct lymphomas developed from descendants of that precursor after acquiring additional separate transforming events. Findings from molecular studies support this notion. Hence, clonally related composite lymphomas are elegant models to study the multistep transformation process in lymphomagenesis. © 2014 Elsevier Ltd.
Mayr G.,Senckenberg Institute
Palaeontology | Year: 2014
Knowledge of the evolutionary history of crown group birds (Neornithes) has significantly improved through emerging congruence among phylogenetic hypotheses and the description of numerous new Palaeogene stem group representatives. However, controversies still persist about the precise interrelationships of many extant and fossil taxa and about the timing of the diversification of the neornithine crown group. Using the example of Phaethontiformes (tropicbirds) and Psittaciformes (parrots), it is shown how new sequence-based phylogenies may shed light on the relationships of fossils with an unexpected character mosaic, and how such fossils can improve our understanding of character evolution in morphologically disparate avian taxa. The earliest occurrences of neornithine birds are plotted on a current phylogeny. As noted by previous authors, an extensive diversification of neornithine birds before the latest Cretaceous is not supported by the fossil record, and the existence of essentially modern-type representatives of Telluraves (the clade including most arboreal birds) in the Cretaceous, such as suggested from molecular calibrations, is highly unlikely. © The Palaeontological Association.
Kvasnicka H.M.,Senckenberg Institute
Current Hematologic Malignancy Reports | Year: 2013
Although the revised World Health Organization (WHO) criteria for the diagnosis and classification of myeloproliferative neoplasms (MPN) were defined by a panel of expert hematopathologists and clinicians, controversy has been repeatedly expressed questioning the clinical usefulness and reproducibility of these diagnostic guidelines. In particular, the distinction between essential thrombocythemia (ET), early/prefibrotic primary myelofibrosis (PMF) and initial stages of polycythemia vera (PV) is still a matter of debate. In this context, it has been argued that clinical correlations with histological features were not firmly substantiated. On the other hand, recently published data from independently performed studies have repeatedly validated the reproducibility of the WHO criteria and provided persuasive evidence that discrimination of early/prefibrotic PMF has a significant impact on the risk of myelofibrotic and leukemic transformation. However, as has been explicitly required, the WHO concept is based on the recognition of characteristic bone marrow patterns and a consensus of clinical and molecular data. © 2013 Springer Science+Business Media New York.
Mayr G.,Senckenberg Institute
Journal of Zoological Systematics and Evolutionary Research | Year: 2011
Recent hypotheses on the higher-level phylogeny of modern birds are reviewed, and areas of agreement and major conflict are detailed, with emphasis being put on congruence among independent molecular and morphological data sets. Although molecular data significantly contributed to a better understanding of avian phylogeny, they do not seem to be free of homoplasy and caution is warranted in the interpretation of some results. The recently proposed 'Metaves' clade is likely to be an artefact of the β-fibrinogen gene, and current molecular data do not yield well-supported phylogenies for some groups whose interrelationships can be resolved with morphological evidence. There exists, however, congruent and strong molecular evidence for several novel clades that were not recognized by morphologists before, and to ease future discussions the terms Picocoraciae (non-leptosomid 'Coraciiformes' and Piciformes) and Aequornithes ('waterbird assemblage') are introduced. Molecular studies further congruently recover some clades, which have not yet been adequately appreciated and are outlined in the present review. © 2010 Blackwell Verlag GmbH.
Kahlke R.-D.,Senckenberg Institute
Quaternary Science Reviews | Year: 2014
Pleistocene Mammoth Faunas were the most successful, cold-adapted large mammal assemblages in the history of the Earth. However, the causes for their emergence can not be attributed only to the global trend of climate cooling which occurred during the Neogene/Quaternary period. The formation of the Eurasian Mammuthus-Coelodonta Faunal Complex was a result of interacting tectonic, geographical, climatic, ecological and phylogenetic processes. The key environmental factors controlling the origin and evolution of Palaearctic cold-adapted large mammal faunas were successive aridification of major parts of Eurasia, rhythmic global climatic cooling with prolonged and intensified cold stages, and increasing continentality. Between 2.6Ma and around 700kaBP, largely independent mammal faunas became established in continental Asian steppe regions as well as in the circumpolar tundra. Both faunal complexes were adapted to open environmental conditions but were largely separated from each other. The principal requirements in order for species to evolve into members of Mammoth Faunas are progressing adaptation to aridity, decreasing temperatures and rapid temperature fluctuations. Eurasian Mammoth Faunas were mainly composed of the descendants of either Central Asian steppe or Arctic tundra faunal elements. The majority of species of Central Asian origin emerged in regions north of the Himalayan-Tibetan uplift. Between 640 and 480kaBP, saiga, musk-ox and reindeer occasionally spread far beyond the limits of their respective traditional areas, thus anticipating the subsequent merge of steppe and tundra originated species in Eurasian Mammoth Faunas. During the pronounced cold period of MIS 12, tundra species regularly expanded south- and southwestward into a newly formed type of biome, the so-called tundra-steppe. In parallel, species originating from the Asian steppe dispersed into new habitats north and northwest of their ancestral distribution areas. This drastic faunal turnover led to the formation of the earliest pan-Eurasian Mammoth Fauna at around 460kaBP. The sister taxa of several species involved in Mammoth Faunas underwent separate evolution in Central Asia, thus indicating ecological differences between the Asian core steppe and Eurasian tundra-steppe habitats. During temperate and humid stages of the late Middle to Late Pleistocene periods the transcontinental reach of the steppe-tundra biome collapsed. As a result, the majority of the characteristic mammal species were forced back to continental steppe or Arctic tundra refugia, only returning during subsequent cold stages when the formation of a new and more evolved Mammoth Fauna began. The maximum geographic extension of the Palaearctic Mammuthus-Coelodonta Faunal Complex occurred during the Late Pleistocene, when it covered an area of up to 190 degrees of longitude and 40 degrees of latitude. © 2013 Elsevier Ltd.
Wisshak M.,Senckenberg Institute
Developments in Sedimentology | Year: 2012
Microbioerosion ichnocoenoses are produced by euendolithic microorganisms including bacteria, cyanobacteria, chlorophytes, rhodophytes, and fungi, which either find shelter from grazers and physical disturbances or seek nutrition within the mineralized substrate they dissolve. Most microborings perfectly match the outline of the organisms producing them and thus can be assigned to their living tracemaker with a fair degree of confidence. A favorable concert of evolutionary longevity and environmental dependency make them superb paleoenvironmental indicators for all Phanerozoic strata that contain well-preserved fossil skeletal material. The present chapter provides the sedimentologist, ichnologist, or paleoecologist with a review of the methodological toolkit at hand to study these microscopic structures (petrographic thin sections, SEM of epoxy resin casts, and microcomputed tomography), a comprehensive overview of microboring biota and the trace fossils they produce, and a review and outlook of their applicability for paleoenvironmental studies with respect to paleobathymetry, paleothermometry, paleosalinity, and paleotrophodynamics. © 2012 Elsevier B.V.
Mayr G.,Senckenberg Institute
Journal of Systematic Palaeontology | Year: 2011
A virtually uncrushed skeleton of Messelastur gratulator from the Middle Eocene of Messel (Germany) is described, which for the first time preserves the feet of this poorly known avian species. The new fossil corroborates a close relationship between Messelastur and the early Eocene Tynskya eocaena, fromwhich M. gratulator differs in its more raptor-like feet. The specimen further shows that the Messelasturidae are the sister taxon of the early Eocene Halcyornithidae ('Pseudasturidae'), which are considered to be stem group representatives of the Psittaciformes. A sister group relationship between Messelasturidae and Halcyornithidae is supported by a phylogenetic analysis of 100 morphological characters, but concerning the extant taxa the results of the primary analysis conflict with current hypotheses on avian higher-level relationships. After constraints were enforced, the analysis resulted in a sister group relationship between the Messelasturidae/Halcyornithidae clade and Psittaciformes. Messelasturids have a raptor-like beak and large processus supraorbitales, and were previously considered to be most closely related to either 'falconiform' or strigiform birds. If future data strengthen their psittaciform affinities, they not only add a distinctive new taxon to the stem lineage of Psittaciformes, but also show that some stem group Psittaciformes were predatory birds. © 2011 The Natural History Museum.
Mayr G.,Senckenberg Institute
Systematics and Biodiversity | Year: 2013
Based on calibrations of molecular phylogenies and biogeographic considerations, it has been argued that the basal divergences of crown group Passeriformes occurred in the late Cretaceous, following the break-up of eastern Gondwana. Some implications of this hypothesis have, however, not yet been adequately addressed. In particular, a Cretaceous divergence of crown group passerines would imply an unprecedented evolutionary stasis for more than 80 million years in one of the most species-rich group of endothermic vertebrates. The temporal distribution and phylogenetic affinities of northern hemispheric fossils further conflicts with current hypotheses on the historical biogeography of passerines, and is in better concordance with a Cenozoic divergence of crown group Passeriformes. © 2013 The Natural History Museum.
Mayr G.,Senckenberg Institute
Zoologica Scripta | Year: 2011
The extinct Cenozoic bony-toothed birds (Pelagornithidae) are characterized by the occurrence of unique spiky projections of the osseous jaws and are among the most distinctive neornithine taxa. Earlier authors considered these marine birds to be most closely related to 'Pelecaniformes' or Procellariiformes, but recent phylogenetic analyses resulted in a sister group relationship to Anseriformes. This latter hypothesis was, however, coupled with a non-monophyly of galloanserine or even neognathous birds, which is not supported by all other current analyses. The character evidence for anseriform affinities of pelagornithids is thus reassessed, and it is detailed that the alleged apomorphies cannot be upheld. Pelagornithids lack some key apomorphies of galloanserine birds, and analysis of 107 anatomical characters did not support anseriform affinities, but resulted in a sister group relationship between Pelagornithidae and Galloanseres. By retaining a monophyletic Galloanseres, this result is in better accordance with widely acknowledged hypotheses on the higher-level phylogeny of birds. The (Pelagornithidae + Galloanseres) clade received, however, only weak bootstrap support, and some characters, such as the presence of an open frontoparietal suture, may even support a position of Pelagornithidae outside crown-group Neognathae. © 2011 The Author. Zoologica Scripta © 2011 The Norwegian Academy of Science and Letters.
Mayr G.,Senckenberg Institute
Zoological Journal of the Linnean Society | Year: 2011
Multiple molecular analyses provide a congruent and well-supported phylogeny of the charadriiform family-level taxa, which conflicts with previous hypotheses based on osteological data. In order to revise the latter and to identify new characters of phylogenetic significance, skeletons of most charadriiform family-level taxa were examined and 49 characters analysed. Tree topology was sensitive to outgroup choice, but the result of the analysis rooted with Columbidae (doves and pigeons) recovered a monophyletic Scolopaci, Charadrii, and nonturnicid Lari. With regard to the inclusion of Alcidae and Glareolidae in the Lari, the results of the present study are also in better concordance with the new molecular phylogenies than previous analyses of morphological data. Furthermore, for the first time an apomorphy of a clade including Thinocoridae, Pedionomidae, Rostratulidae, and Jacanidae was identified. Inclusion of Turnicidae in the Lari could not be supported, but there is no strong morphological evidence for an alternative placement. Pluvianus shares derived osteological features with the Burhinidae, and its position in the molecular analyses likewise cannot be corroborated with morphological data. Based on the topology of the molecular consensus tree, the ancestral state of selected characters is reconstructed. It is finally noted that recent calibrations of molecular analyses, which indicate an origin of extant charadriiform lineages in the Cretaceous, are based on incorrectly identified fossils. © 2011 The Linnean Society of London.