Abstract

The phylogenetic significance of archeopyles in calcareous dinoflagellates cysts has been evaluated, and a classification model is developed that focuses on the archeopyle categories and types established for organic-walled dinoflagellates by Evitt (1967, 1985). Several of Evitt's archeopyle categories are presently recognized within the calcareous dinoflagellate cysts: apical, intercalary, and combination archeopyles, which are here subdivided into eight archeopyle types and several variations. Archeopyles that cannot be assigned to a distinct type, and those with outlines that do not allow an accurate interpretation, are together placed in a separate category: miscellaneous archeopyles. The stratigraphic distribution of the different archeopyle types reveals a phylogenetic trend characterized by an increase of the number of plates involved in archeopyle formation. The first calcareous dinoflagellate cysts to appear in the late Triassic have a monoplacoid apical archeopyle. The first taxa that show an archeopyle involving more than one plate are from the Early Cretaceous, with the first triplacoid apical archeopyle appearing at the Berriasian/Valanginian boundary. This is followed by the first combination archeopyle, which includes six plates, in the middle Aptian. Epitractal archeopyles originated no earlier than the early Oligocene. At the beginning of the Paleogene, species with a combination archeopyle increased in abundance, progressively replacing species possessing an apical archeopyle that dominated during the Mesozoic. Newly described species are: Calciodinellum clamosum, accommodating the two subspecies Calciodinellum clamosum subsp. clamosum Autonym, and Calciodinellum clamosum subsp. latum; Calciodinellum kerguelense; Fuettererella belliata; and Pernambugia? patata. New combinations are: Cervisiella operculata (Bramlette and Martini, 1964); Praecalcigonellum sulcatum (Keupp, 1979a); and Praecalcigonellum dolium (Keupp, 1979b). Because of the new interpretation of their archeopyles we emend the following genera: CervisiellaHildebrand-Habel, Willems, and Versteegh, 1999; EchinodinellaKeupp, 1980; FuettererellaKohring, 1993a; and Pernambugia Janofske and Karwath inKarwath (2000). The species Orthopithonella? minuta and Pirumella johnstonei, which have been previously synonymized with Fuettererella deflandrei, are retained as independent taxa.

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