Early evolution of the genus Eoparastaffella (Foraminifera) in Eurasia: the interiecta group and related forms, late Tournaisian to early Viséan (Mississippian).
| Autoři | |
|---|---|
| Rok publikování | 2007 |
| Druh | Článek v odborném periodiku |
| Časopis / Zdroj | Journal of Foraminiferal Research |
| Fakulta / Pracoviště MU | |
| Citace | |
| Obor | Geologie a mineralogie |
| Klíčová slova | foraminfers; Tournaisian-Visean boundary; Eoparastaffella |
| Popis | Eoparastaffella is a stratigraphically important genus because the first appearance of Eoparastaffella simplex Vdovenko, 1954 from primitive Eoparastaffella of the late Tournaisian was chosen by the Subcommission on Carboniferous Stratigraphy (SCCS) as the primary tool for recognition of the base of the Viséan. Common representatives of Eoparastaffella interiecta Vdovenko, 1971 and related forms were encountered during study of sections spanning the Tournaisian-Viséan boundary in several regions of Eurasia (northwest and northeast Europe, northern Iran and southern China). The study was part of a larger SCCS research project to find a new global boundary stratotype section and point (GSSP) for the base of the Viséan.Eoparastaffella interiecta was previously known only from the Viséan of the former USSR. Two new species, Eoparastaffella vdovenkoae n. sp. and Eoparastaffella macdermoti n. sp., and two unnamed new subspecies are described herein from the collected material. The morphologically related species Eoparastaffella florigena (Pronina, 1963) and Eoparastaffella tumida (Pronina, 1963) are discussed. A biometric study utilizing Principal Component Analysis (PCA) was carried out, in addition to classical morphological descriptions, in an attempt to characterize objectively the morphospace occupied by these taxa and to illustrate their intraspecific variability. The abundant material also allows the description of the juvenile forms of each taxon. The evolutionary history of the first Eoparastaffella is discussed and the biostratigraphic interest of the newly proposed taxa is assessed. The study demonstrates that the first representatives of the genus appeared in the upper part of the Scaliognathus anchoralis europensis conodont biozone and that they diversified rapidly in the latest Tournaisian and earliest Viséan. Together with the wide distribution of Eoparastaffella across Eurasia, this rapid diversification suggests that the genus can be used to increase stratigraphic resolution across the Tournaisian-Viséan boundary interval. Moreover, the evolution documented in the latest Tournaisian reinforces the choice of Eoparastaffella simplex as the guide for the base of the Viséan as its entry level can be also recognized or bracketed with other taxa (other species of Eoparastaffella, other foraminifers and conodonts). |
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