EARLY EVOLUTION OF THE GENUS EOPARASTAFFELLA (FORAMINIFERA) IN EURASIA: THE 'INTERIECTA GROUP' AND RELATED FORMS, LATE TOURNAISIAN TO EARLY VISEAN (MISSISSIPPIAN)

摘要

Eoparastaffella is a stratigraphically important genus as the 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 (western and central Europe, northern Iran and southern China). Eoparastaffella interiecta was previously known only from the Viséan of the former USSR and Bulgaria. Two new species, Eoparastaffella vdovenkoae n. sp. and Eoparastaffella macdermoti n. sp., and two unnamed new subspecies are described herein from abundant new material. The morphologically related species Eoparastaffella florigena (Pronina, 1963) and Eoparastaffella tumida (Pronina, 1963) are discussed. A biometric study is 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 early Eoparastaffella is discussed and the biostratigraphic interest of the newly proposed taxa is assessed.