Cornet L.,University of Liege |
Gerrienne P.,University of Liege |
Meyer-Berthaud B.,Montpellier University |
Meyer-Berthaud B.,French National Center for Scientific Research |
Review of Palaeobotany and Palynology | Year: 2012
A permineralized Callixylon trunk is reported from Ronquières, a mid to late Givetian (Middle Devonian) locality from Belgium. The specimen consists of an 80. cm long trunk adpression whose central area is preserved as a pyrite permineralization. The pyritized area is composed of a eustele surrounded by secondary xylem. Tracheids show radially aligned groups of pits separated by unpitted regions on the radial walls of tracheids. The specimen belongs to a group of species characterized by a predominance of uniseriate rays and the lack of ray tracheids. This Callixylon specimen is one of the earliest representatives of the genus. It coexists at the locality with large cladoxylopsids and provides direct evidence that the tree habit had evolved in the archaeopteridalean progymnosperms by the Givetian. © 2012 Elsevier B.V.
Castiglia R.,University of Rome La Sapienza |
Solano E.,University of Rome La Sapienza |
Makundi R.H.,Sokoine University of Agriculture |
Hulselmans J.,University of Antwerp |
And 2 more authors.
Journal of Zoological Systematics and Evolutionary Research | Year: 2012
The mesic four-striped grass rat Rhabdomys dilectus De Winton, 1897 is distributed in mesic regions of southern and eastern Africa. We carried out a molecular and chromosomal study of the northernmost populations of the species to provide insight into the subspecific boundaries identified within the species and to describe its genetic structure in Eastern Africa. Maximum likelihood, maximum parsimony and neighbour-joining methods were used to construct phylogenetic relationships among all the haplotypes belonging to the large part of the species range. Times of divergences were estimated assuming a relaxed molecular clock with two calibration points. We identified three well-supported clades within R. dilectus. One basal clade corresponding to Rhabdomys d. chakae (2n=48) is found in South Africa. Two additional sister clades corresponding to R. d. dilectus (2n=48 and 2n=46) are allopatrically distributed in southern and northern parts of the species range. Genetic divergence among the three clades is relatively high (ranges 4.2-5.7%). A very divergent new karyotype 2n=38, FNa=60 was found in two high-altitude populations on Mt. Meru and Mt. Kilimanjaro. The karyotype differences consist in three Robertsonian fusions and one whole-arm reciprocal translocation. Interestingly, the mtDNA phylogeny does not match with the diploid numbers. In fact, the 2n=38 specimens form a monophyletic group within a clade that includes specimens with the 2n=46 karyotype that appears as paraphyletic. We estimated the new karyotype originated in peripatric condition during the last phases of the Pleistocene. This study confirms the importance of chromosomal analysis in detecting taxonomic units and cryptic diversity in rodents. © 2011 Blackwell Verlag GmbH.
Storme J.-Y.,University of Namur |
Storme J.-Y.,University of Liege |
Steurbaut E.,RBINS |
Steurbaut E.,Catholic University of Leuven |
And 5 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2014
The Global Boundary Stratotype Section and Point for the base of the Selandian Stage is defined in the Zumaia section (Spain) at an abrupt change in lithology (base of Itzurun Formation), which coincides with the onset of a negative carbonate carbon isotope shift. However, this lithological change is not always very well expressed in other sections. In order to document the stratigraphic position of the Danian/Selandian boundary (DSB) on a more global scale, we have investigated three sections across the DSB, the Zumaia reference section (GSSP), the Loubieng section (auxiliary DSB reference section, France) and the Sidi Nasseur section (Tunisia). The Danian/Selandian boundary interval is subdivided and correlated throughout low latitudes, from the Altlantic Bay of Biscay to the Southern Tethys, on the basis of seven calcareous nannofossil and planktonic foraminiferal events (E-events). The base of the Selandian is proved to coincide with the end of the Braarudosphaera acme, which correlates with the lowest consistent occurrence (LCsO) of Lithoptychius aff. bitectus (=Fasciculithus janii sensu Steurbaut and Sztrákos, 2008) (event E4), but which is slightly posterior to the second radiation of the fasciculiths, up to now considered to represent the primary correlation tool of the DSB. A short-term δ13Corg negative excursion, associated with an increase in pCO2 is recorded at the very base of the Selandian. It is interpreted as a short period of global warming (hyperthermal), the duration of which is estimated at ~30kyr. It is followed in all the three studied sections by a long-term decoupled carbon isotope event, marked by increasing δ13Corg and decreasing δ13Ccarb values. It may reflect a period of climatic cooling of a few 100kyr, interpreted as a possible precursor of the global cooling event, marking the late Paleocene in the North Atlantic realm. The integration of the biostratigraphic and the isotope data indicates major differences in sedimentation rates during the early Selandian in the studied sections, but there is no evidence of substantial breaks in sedimentation in any of the sections during this interval. The lithological shift at the base of the Selandian points to an abrupt palaeoenvironmental reorganisation, although our integrated bio-chemostratigraphical investigation does not allow for estimating its duration nor the presence of a hiatus at that time. © 2014 Elsevier B.V.
The Palaeocene/Eocene boundary section at Zumaia (Basque-Cantabric Basin) revisited: New insights from high-resolution magnetic susceptibility and carbon isotope chemostratigraphy on organic matter (δ 13C org)
Storme J.-Y.,University of Namur |
Devleeschouwer X.,RBINS |
Schnyder J.,CNRS Paris Institute of Earth Sciences |
Cambier G.,RBINS |
And 5 more authors.
Terra Nova | Year: 2012
The Zumaia section, the most complete and representative section of the early Palaeogene (hemi)-pelagic succession of the Pyrenees, is widely acknowledged as a key reference for the Palaeocene-Eocene boundary. New high-resolution δ 13C org of the Zumaia section (-23.8 to -28.8‰) confirms the position of the Carbon Isotope Excursion and enhances the distinction between the different steps of the CIE/PETM event. According to new magnetic susceptibility data and detailed cycle counting, the entire duration of the CIE/PETM in Zumaia is estimated in ∼168±16ka. Moreover, the investigation of palynofacies and low-field magnetic susceptibility reveal significant detrital influx during the interval. Several magnetic susceptibility phases and trends are recognised and are interpreted in terms of sea-level fluctuations before, during and after the PETM. Coupled with results from other sections, our data reveal the presence of an unconformity followed by an eustatic sea-level rise (TST) in the latest Palaeocene. © 2012 Blackwell Publishing Ltd.
Johan Kotze D.,University of Helsinki |
Brandmayr P.,University of Calabria |
Casale A.,University of Sassari |
Dauffy-Richard E.,IRSTEA |
And 16 more authors.
ZooKeys | Year: 2011
'Carabidologists do it all' (Niemelä 1996a) is a phrase with which most European carabidologists are familiar. Indeed, during the last half a century, professional and amateur entomologists have contributed enormously to our understanding of the basic biology of carabid beetles. The success of the field is in no small part due to regular European Carabidologists' Meetings, which started in 1969 in Wijster, the Netherlands, with the 14 th meeting again held in the Netherlands in 2009, celebrating the 40 th anniversary of the first meeting and 50 years of long-term research in the Dwingelderveld. This paper offers a subjective summary of some of the major developments in carabidology since the 1960s. Taxonomy of the family Carabidae is now reasonably established, and the application of modern taxonomic tools has brought up several surprises like elsewhere in the animal kingdom. Progress has been made on the ultimate and proximate factors of seasonality and timing of reproduction, which only exceptionally show non-seasonality. Triggers can be linked to evolutionary events and plausibly explained by the "taxon cycle" theory. Fairly little is still known about certain feeding preferences, including granivory and ants, as well as unique life history strategies, such as ectoparasitism and predation on higher taxa. The study of carabids has been instrumental in developing metapopulation theory (even if it was termed differently). Dispersal is one of the areas intensively studied, and results show an intricate interaction between walking and flying as the major mechanisms. The ecological study of carabids is still hampered by some unresolved questions about sampling and data evaluation. It is recognised that knowledge is uneven, especially concerning larvae and species in tropical areas. By their abundance and wide distribution, carabid beetles can be useful in population studies, bioindication, conservation biology and landscape ecology. Indeed, 40 years of carabidological research have provided so much data and insights, that among insects - and arguably most other terrestrial organisms - carabid beetles are one of the most worthwhile model groups for biological studies. © DJ Kotze et al.