HOW PLASTIC IS VENDOBIONTA MORPHOLOGY? A GEOMETRIC MORPHOMETRIC STUDY OF TWO GROUPS OF PTERIDINIUM FROM THE LATEST NEOPROTEROZOIC

The analysis and interpretation of Vendobionta morphology is critical to elucidating a range of issues about their ontogeny and evolution, as well as life habits. These analyses, however, are complicated because these organisms are often morphologically enigmatic and defy ready categorization within modern taxonomic schemes. This study delves into the morphology of one of these problematic groups: Pteridinium. Specimens were investigated from two localities, Namibia and North Carolina, using geometric morphometrics. The landmark data, which was analyzed to compare specimens based on locality, taphonomy, and preservation, were subjected to three statistical tests: Principle Components Analysis, Procrustes shape analyses, and Foote’s disparity test. All tests revealed no distinct clustering within or by either group due to any of the variables. All variables plotted within the same 95% confidence ellipses, displaying a lack of statistical support for the distinctness of these groups. Therefore, the most parsimonious reason for the lack of differences observed by these two groups stem from them being part of the same morphological group, a conclusion that places into question the validity of the inclusion of two separate species in the genus Pteridinium.