Quantitative biostratigraphical ranges of some late Cenozoic species of the dinoflagellate genusSpiniferitesand taxonomic considerations

Abstract

A new quantitative biostratigraphical method, based on an 'index of stratigraphical abundance' (ISA), has been used to refine the stratigraphical range of 50 dinoflagellate cyst taxa. Most of these correspond to Quaternary representatives of Achomosphaera or Spiniferites. Some extinct taxa are also discussed when their morphology is close to that of recent species (e.g. Spiniferites lenzii, S. twistringiensis and S. pseudofurcatus), as well as some species possibly related to the motile Gonyaulax spinifera complex. The ISAs of S. mirabilis and S. hyperacanthus are similar, as well as for S. elongatus and S. sphaericum. Although initially presumed as indicating morphotypes of a same taxon, it seems rather that the ISAs similarites must be interpreted as an indication of close ecological preferences. The emergence of forms of Spiniferites with low to absent septa appears relatively late (compared to the range of the genus), but the first occurrence of intergonal processes is relatively early, indicating that it is probably a character deeply rooted into the generic genome. The previously calculated phylogeny of some Gonyaulax motile cells shows a different tree pattern than the stratigraphical first appearance succession of their presumed cyst equivalents.

An overview and brief description of common marine organic-walled dinoflagellate cyst taxa occurring in surface sediments of the Northern Hemisphere

“…Lowest stratigraphic occurrence. Lower Eocene (e.g., Costa and Downie, 1979;Brown and Downie, 1984;Islam, 1984;Cocozza and Clarke, 1992), possibly the Lower Paleocene (Jan du Chêne, 1988;Eshet et al, 1992), and commonly recorded through the Quaternary (also see discussion in Londeix, 2018). (Londeix et al, 2018).…”

“…Lowest stratigraphic occurrence. The lowest common occurrence of Spiniferites bulloideus sensu stricto is in the Lower Eocene (e.g., Auffret and Gruas-Cavagnetto, 1975;De Coninck, 1975; also see discussion in Londeix, 2018). The lowest occurrence of Spiniferites bulloideus sensu Wall, 1965 is probably Lower Miocene (e.g., Londeix and Jan du Chêne, 1998), but records of this species are mostly from the Holocene.…”

“…Occasional occurrences in the Lower (Powell, 1988;Williams et al, 1993) and Middle Miocene of the Porcupine Basin (e.g., Harland 1979;Louwye et al, 2008). The species becomes more frequent in the Pliocene and the Quaternary (see Londeix, 2018).…”

“…Recorded from the Lower Miocene (e.g., Edwards, 1986;Powell, 1986) and common through the Quaternary. Older occurrences are considered problematic (Londeix, 2018). (Wall and Dale, 1968).…”

Taxonomy and operational identification of Quaternary species ofSpiniferitesand related genera

“…145 Ma (from earliest Cretaceous to the present). Assignment of Quaternary specimens to Spiniferites ramosus is discussed below in taxonomic remarks as well as in Londeix (2018).…”