SPECIES DIFFERENTIATION IN THE PERMIAN GENUS HAMIAPOLLENITES WILSON, 1962 IN OKLAHOMA

In February 1962, Wilson established the genus Hamiapollenites for bisaccate pollen grains with striae (= taeniae) on the proximal surface that extend from saccus to saccus, and on the distal surface that are oriented 90° to the proximal striae. Jizba (1962) erected Striatosaccites, now a synonym, for the same form seven months later. Species within the genus are differentiated primarily on the basis of the number and width of proximal and distal striae (and the combination of both), and on their width of the furrows between. Additional species have been based on differences in ornamentation (e.g., spines). The genus is most commonly found in Permian sediments, but has been reported from as early as the Late Pennsylvanian; its affinity is considered to lie among peltasperm seed plants.

Here we investigate species differentiation in Permian Hamiapollenites by sampling grains in multiple samples in multiple cores through the Wellington Formation (Sumner Group: Permian) of Oklahoma. By measuring numbers and widths of striae and furrows, sizes of the corpus and sacci, and describing ornament, we seek to discover and quantify morphological variation at various scales—within samples, between samples in a section, and among sections—in order to differentiate repeatable clusters of morphology indicative of different species.

Initial studies have focused on variation within samples and although there is substantial variation, multivariate analyses based on those measurements have produced no evidence for the occupation of distinct areas in morphospace. Although our analyses may provide evidence for or against those species concepts evident in the literature, ultimately, sampling the contents of individual sporangia from polleniferous organs will provide the best evidence of true species diversity.