Original paper

Multivariate morphometric analyses of phyllocrinids (Crinoidea) from the Štramberk limestones

Tręzsiok, Dawid; Salamon, Mariusz A.

Abstract

The taxonomic validity of some crinoid species belonging to the genus Phyllocrinus from the Štramberk limestones has been the source of confusion and uncertainty. It has been long argued that the morphology of interradial processes is the primary character differentiating phyllocrinid species. However, it has been pointed out recently that the morphology of interradial processes varies widely and that the number of phyllocrinid species from the Štramberk and the so-called Štramberktype limestones may be overestimated. Here, we use multivariate methods to determine morphogroups among six Late Jurassic-Early Cretaceous populations of three phyllocrinid species (Phyllocrinus malbosianus, P. sinuatus, and P. stellaris) from two localities (Poland and Czech Republic). Using four simple morphological characters, we tested for taxonomic separation among these populations. Principal component analysis results show a clear separation of the three species in the morphospace, although geographic separation among populations of the same species is less clear. However, examined populations display different allometric trajectories. Furthermore, the size-free canonical variate analysis revealed six size-invariant morphogroups that are statistically distinct. These results do not match predictions provided by traditional classification in the diagnosis. In contrast to previous suggestions, our results show that the number of phyllocrinid species from the Štramberk and Štramberk-type limestones is not overestimated. It is unknown whether the observed differences among populations from the two localities are due to the extreme phenotypic plasticity or to the presence of so far undescribed species.

Keywords

cretaceouscrinoidsallometryjurassicczech republicpolandcyrtocrinids