Cichlid biogeography: comment and review

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72313/1/j.1467-2979.2004.00148.x.pd

An enigmatic gnathostome vertebrate skull from the Middle Devonian of Bolivia.

International audienc

Diversification trajectories and evolutionary life-history traits in early sharks and batoids

Different interpretations on the timing of early diversification and radiation of modern sharks and batoids (Neoselachii) in the Earth's history exist and are related to discrepancies in taxonomic and phylogenetic interpretations favouring a Late Triassic or earliest Jurassic diversification and subsequent radiation event, respectively. Sampling standardization based on pooled taxonomic occurrences made it possible to overcome the problem of a much richer neoselachian record in the Late Jurassic than earlier on. The standardized pattern of genus richness is one of low and fairly constant diversity in the Late Triassic and earliest Jurassic with a steep rise in the Toarcian (ca 180 Myr ago), representing the maximum diversification rate in the Jurassic towards a Middle and Late Jurassic plateau. The major Toarcian diversification agrees with the conclusions based on phylogenetic analyses, but is in conflict with older interpretations based on raw data. Early Jurassic expansion of neoselachians was opportunistic in the aftermath of the end-Triassic mass extinction and the reasons for their rapid diversification and radiation probably include small body size, short lifespans and oviparity, enabling faster ecological reorganizations and innovations in body plans for adapting to changing environmental conditions

Development of a miniaturised picosecond streak camera Part 1: cathode stability and initial electrode design

SIGLELD:6029.315(NPL-DES--72). / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Isotope and elemental geochemistry of black shale-hosted fossiliferous concretions from the Cretaceous Santana Formation fossil Lagerstätte (Brazil)

© 2016 The Authors. Sedimentology © 2016 International Association of SedimentologistsCarbonate concretions hosted within organic carbon-rich shale sequences represent unique archives of often exceptionally preserved fossil biota. Besides providing high-fidelity preservation, their geochemical signatures can provide insight into the physical and chemical processes during early and later-stage concretion growth. Here, two fossiliferous carbonate concretions of the late Early Cretaceous Santana Formation (Araripe Basin, north-east Brazil) are analysed with an integrative geochemical approach including µ-XRF scanning, d13C, d18O, 87Sr/86Sr and ?47 (clumped isotope thermometry). Individual concretions show a concentric internal zonation with the outermost layer being composed of millimetre thick cone-in-cone calcite. A strong covariance of d13C and d18O values of the fine-crystalline concretion body indicates mixing of two different carbonate phases and supports a scenario of temporally separated pervasive growth stages. Microbially-mediated formation of an early porous calcite framework was controlled by the combined processes of fermentation and methanogenesis around the decaying carcass, forming localized environments within a zone of sulphate reduction. Microbial sulphate reduction is indicated by the concentric enrichment of pyrite in the outer part of the concretion body and by high pyrite abundance in the surrounding shale. Information on the later-stage diagenetic processes affecting the Santana concretions can be derived from the outermost fringing cone-in-cone calcite. The carbonate precipitating fluid was characterized by a more or less marine d18O composition (calculated d18Oporewater = -1·0 to -1·8‰) and by radiogenic Sr-isotope ratios (up to 0·713331 ± 7·0*10-6), the latter probably reflecting modification due to interaction with the surrounding shale or, alternatively, with underlying evaporitic sulphate deposits influenced by strong continental inflow or with crystalline basement rocks. The ?47-derived temperature estimates range between 37°C and 42°C ± 5, indicating precipitation of the cone-in-cone calcite at a depth of 650 to 850 m, which is only half as much as the maximum burial depth derived from existing fission-track data. Overall, the study of fossiliferous carbonate concretions in organic carbon-rich sedimentary sequences can reveal a complex growth history spanning incipient microbially-influenced precipitates as well as later-stage burial diagenetic phases

Estudo do escápulo-coracóide e da cartilagem sinarcual cérvico-torácica de Rhinoptera brasiliensis Müller & Henle e Rhinoptera bonasus (Mitchill) Elasmobranchii, Rhinopteridae) Study of the scapulocoracoid and cervico-thoracic synarcual cartilage of Rhinoptera brasiliensis Müller & Henle and Rhinoptera bonasus (Mitchill) (Elasmobranchii, Rhinopteridae)

<abstract language="eng">A comparative analysis of the scapulocoracoid and cervico-thoracic synarcual cartilage of juvenile specimens of Rhinoptera brasiliensis Müller & Henle, 1841 and R. bonasus (Mitchill, 1815) was accomplished, in order to identify specific, individual and ontogenetic differences. In the scapulocoracoid, the scapular foramen and the posterodorsal fenestra is larger in R. brasiliensis. The anterior fenestra bridge is thicker and the metacondyle is thinner and longer in R. bonasus. This species also possesses a larger re-entrance between the mesocondyle and the metacondyle, as well as in the fitting region of'the synarcual cartilage, placed close to the scapular process. The individual differences are: posteroventral fenestra with variable diameter independent of the size of the specimens; scapulocoracoids, in some specimens, are more fragile even if they have been kept in the same conservation conditions. In the cervico-thoracic synarcual cartilage, the lateral stay in R. brasiliensis encloses completely the superior portion of the anteroscapular bridge. There are three more prominent condyles beside the suprascapula in R. brasiliensis, R. bonasus, however, shows a protuberance close to the suprascapula, inconspicuous and more distant from the scapular lamina. Several specimens of different size of R. bonasus show a synarcual cartilage wider in ventral view and higher in lateral view. In the majority of specimens, the number of ventral spinal foramina is higher than the dorsal ones in both species. R. bonasus has only one pair of asymmetric basal foramina, whereas R. brasiliensis possesses three or four foramina. Regarding individual differences, at least one specimen of R. bonasus exhibits a single basal foramen