Sprecher
Beschreibung
The term ‘peteinoid acritarchs’ derives from the genus Peteinosphaeridium Staplin, Jansonius and Stanley 1965 from Öland (Sweden). They are described in the literature as displaying a large morphological variability in their processes. This had been noticed and discussed by Alfred Eisenack since the 1930s, who evoked caution when assigning new species and/or genera. However, several new species and genera were described years after the creation of the genus Peteinosphaeridium leading to an inflation of their diversity and creating difficulties in their classification. Now, besides Peteinosphaeridium, the group contains the genera Asketopalla Loeblich and Tappan 1969, Polyancistrodorus Loeblich and Tappan 1969, Rhopaliophora Tappan and Loeblich 1971, Cycloposphaeridium Uutela and Tynni 1991, and Liliosphaeridium Uutela and Tynni 1991. A literature revision of this group and the assessment of its morphological variability were carried out by bivariate statistics for the literature data, and by multivariate statistics for Öland specimens. Bivariate statistical tests showed that, compared to vesicle diameter, processes length displays more variability among genera. Processes length suggests similarities for Asketopalla–Rhopaliophora and Peteinosphaeridium–Polyancistrodorus. For the multivariate analysis, the PCA and LDA (CVA) revealed three different morphotype groups based on the complexity of process morphology. Multivariate statistical tests suggest that the three genera identified from Öland slides, i.e. Peteinosphaeridium, Liliosphaeridium and Rhopaliophora, are significantly different in terms of process morphology. However, at species rank, this difference becomes difficult to distinguish. Peteinoid acritarchs may have better biostratigraphic applications at the genus rank. Hypotheses such us ‘paleo-provinces’ or endemism of peteinoid acritarch should be re-assessed.