Biometric analysis of the Arkhangelskiella group in the upper Campanian-Maastrichtian of the stevns-1 borehole, Denmark: taxonomic implications and evolutionary trends

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The taxonomy of the calcareous nannofossil Arkhangelskiella is revised using the results of a biometric analysis performed on 599 specimens from various stratigraphic levels throughout the upper Campanian-Maastrichtian of the Stevns-1 borehole, Denmark. Combined qualitative labelling and biometric measurements suggest that this genus comprises at least three distinct morphogroups in this stratigraphic interval, with possibly one additional morphotype. The results show that the descriptions formerly used for the erection of these groups as distinct species do not fit to their observed range in the coccolith length and in the rim width, and that the central opening is an important additional parameter allowing distinction between the different morphogroups. Biometric analysis shows, however, that the morphogroups are strongly overlapping on all measured parameters. Therefore, the three distinct variants of Arkhangelskiella cymbiformis (var. NT, var. N and var. W) formerly described by Varol are reintroduced and emended rather than using distinct species. In addition, a fourth variant is described, A. cymbiformis var. SW. Using observed relationships between the parameters as well as stratigraphic ranges of these groups throughout the latest Cretaceous, evolutionary trends are outlined.
Original languageEnglish
JournalGeobios
Volume43
Issue number6
Pages (from-to)639-652
Number of pages13
ISSN0016-6995
DOIs
Publication statusPublished - 2010

ID: 18485911