Fourier shape analysis of Upper Cretaceous Normapolles from southern Sweden

Abstract

Abstract Pollen grains of three previously described species of Upper Cretaceous dispersed Normapolles from souther Sweden, Extratriporopollenites (Oculopollis) triceps Skarby, E. (Trudopollis) artifex Weyland & Krieger and E. (Trudopollis) firmus Skarby, and specimens extracted from a single anther (identified as E. artifex), have been analyzed by Fourier analysis. The purpose was to assess quantitatively the diagnostic significance of the outer and inner equatorial contour, and also the validity of the species. Seventy-two radii were measured at equal angular increments along the outer and inner contour, and Fourier series were fitted to the resulting curves. The shapes of the pollen grains may be described by the average radius (zeroth harmonic) and a series of cosine curves relating to their three-fold symmetry (third, sixth, nineth through twenty-fourth harmonic). Multivariate analyses of these harmonics show that E. firmus, which lacks prominent apertures, stands out as a distinct species. The specimens from the single anther fall within the range of T. artifex. Some specimens identified as E. triceps overlap with T. artifex, indicating that the apertures in this species, described as well-developed, may approach the less prominent apertures of T. artifex. The results emphasize the difficulties in separating the genera Oculopollis and Trudopollis Pflug. Typical specimens can be identified, but not intermediate forms. In order to solve this problem a thorough quantitative analysis of dispersed specimens and pollen from anthers is necessary.