Chewing function and feeding adaptations in early Palaeogene mammals with quadritubercular molars

点击翻译按钮获取中文摘要

A crucial step in early Palaeogene mammal evolution was the origin of the quadritubercular molar. The addition of a fourth cusp (hypocone) at the upper molar was a first shift from the basal tribosphenic pattern to molars with enlarged occlusal surface and increased grinding and crushing function. This made the utilisation of a wider array of food sources possible, especially of tough plant material and contributed essentially to the great success of the mammals in colonizing virtually all kinds of environments. However, up to now there are virtually no studies that have investigated the functional implications of this fundamental reorganisation of the mammalian molars. Especially, there is a lack of quantifying studies that demonstrate the efficiency of mastication. The project aims to compare the functional patterns of the different basal quadritubcercular molar constructions of early Palaeogene mammals in order to figure out similarities and differences. An important goal is the virtual simulation of the mastication cycle with the OFA-software which has been especially designed for that purpose. With the OFA for the first time functional contact areas and cutting edges of the molar occlusal surface can be visualized and quantified based on µCT-3D models. Additionally, micro-texture analyses that will be conducted with the µ-surf high resolution confocal microscope provide information on the diet. In our study we will test dietary adaptations of various Paleocene mammal groups (e.g. Macroscelidea, Plesiadapiformes, condylarths) that have been postulated earlier based on traditional parameters (e.g. tooth crown morphology), in order to better understand their role in the post-Cretaceous ecosystems. We expect fundamental new insights into the first phase of differentiation of the tribosphenic molar that initiated the great differentiation and unparalleled success of mammals in Cenozoic ecosystems.