Niche Differentiation within the Crinoid Community from the Lower Devonian Hunsrück Slate, Germany

The Lower Devonian Hunsrück Slate exhibits a remarkable diversity of stalked crinoids, with approximately 61 species from 31 genera, representing all major Paleozoic taxa. Among them are forms with highly branched or unbranched arms, with or without pinnules. Prominent anal tubes or spines are present in many species. The calyces are typically small, and the stalks relatively slender and of varying lengths.

This study investigates the composition of this crinoid community, assessing whether the individuals coexisted in competition or if the community structure provides benefits to them. The latter is assumed, because the great variety of different forms, especially in the construction and branching of the arms, indicates that these crinoids possessed a wide food spectrum.

To test this hypothesis, the model of niche differentiation by Ausich (1980) is applied. The most important parameters are column length, which indicates the level of filtration above the seafloor, and filtration fan density, from which information about the food particle selection can be derived.

Fossil material from the Lehmann Collection at the University of Bonn was investigated. Radiographs were taken of the specimens to make all structures visible. Filtration fan densities were calculated for as many genera and species as possible. The results reveal clear differences between the taxa depending on their typical arm-branching patterns and presence or absence of pinnules. To advance this study, column lengths, and more parameters, such as arm width or ambulacral groove width, will be included in the niche differentiation analysis.