A global Chitinozoan biozonation for the Silurian Period is proposed. Each biozone is an interval range defined by the first occurrence of an index species, selected from well-defined species with a relatively short biostratigraphic range. To be included in the scheme, index species must have been recorded from at least two major Silurian palaeocontinents where usable Chitinozoa assemblages have been studied, that is, Avalonia—Baltica (which had already undergone collision by the Silurian), Laurentia, Gondwana and Southern China. Seventeen biozones are identified with seven in the Llandovery: the fragilis, postrobusta, electa, maennili, alargada, dolioliformis and longicollis biozones; four in the Wenlock: the margaritana, cingulata, pachycephala and lycoperdoides biozones; three in the Ludlow: the elongata, philipi and barrandei biozones; and three in the Přídolí: the kosovensis, elegans and superba biozones. Chronostratigraphic calibration is partly provided by reference to the range of the appropriate Chitinozoa index species in the global stratotype sections and points (GSSP) of the Silurian series, e.g. in Bohemia (Czech Republic) for the Přídolí and the Welsh Borderland in England for the Ludlow and part of the Wenlock. When this information was not available, independent biostratigraphic control was provided by calibration with graptolite biozones or in a few cases, conodont or trilobite biozonal schemes. The index and most characteristic species of each biozone are illustrated and their total stratigraphie range provided.

Relationships between various Lower Silurian chitinozoan assemblages are established using statistical methods such as calculation of the number o{ species in common and similarity coeffrcient. conclusions clearly indicate that Eastern canadian chitinozoan f"on" ^rô distinct from those of the norttr Gondwana margin. The proposed relationships are refrned by the "r" oi-Àà." rigorous analytical techniques such as correspondence analysis and cluster analysis' The results are compared to th" plleogeographic reconstructions available for the ordovician and the Lower Silurian' They show that chitinozo^rr, "i" .rr"frrf.rot only {or stratiSrâphic correlations, but also, as their paleogeographic Àrtiil.rtion seems to be linked to paleolatitudes, they can be used to document plate tectonic dynamics' 62I-629l @ t992by The University of Chicago. AI1 rights reserved.

No abstract

No abstract

(Llandoverian, Canada) were studied using image analysis. After digitalization of the objects, shape parameters were calculated. The boundary of each fossil was then traced by a vector centred at the centroid for Fast Fourier Transform (FFT). Results of the two methods were used as variables in a hierarchical cluster analysis in order to group the samples. These results show that Chitinozoa can be significantly classified in terms of taxa using independent shape parameters obtained by image analysis.