Dental function and dietary adaptations of hyracoid mammals

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Hyracoids are a mammalian group of African origin (Afrotheria) that played an important role in Paleogene and Neogene ecosystems of Africa, Asia Minor, and southern Europe. Nowadays their diversity is reduced to few rabbits sized rock dwelling species in northern Africa and the Near East. During the Paleogene and lower Neogene they were dominating herbivores in mammal communities of northern Africa and adjacent regions, ranging in size from mouse to rhinoceros. These giant hyraxes played in northern African palaeocommunities (e. g., Fayum) the role of megaherbivores. During the Neogene this role was successively taken over by ungulates. Hyraxes are also of particular interest, because independently from hoofed mammals (ungulates) they have evolved dentitions which are strikingly similar to those of rhinoceroses and equoids with low crowned teeth. Similar to rhinoceroses, the upper cheek teeth of hyraxes possess a pronounced W-shaped external cutting edge (ectoloph). Differing from rhinos and other herbivores, hyraxes used (and still use today) this ectoloph for lateral food ingestion, whereas rhinos use their front teeth for food intake. This indicates an important functional difference between hyrax and ungulate dentitions that possibly contributed to the later decline of hyraxes and their replacement by ungulates. In contrast to the function of ungulate dentitions that has been intensively investigated in the past, the function of hyrax dentitions is poorly studied so far. Our proposal aims to close this important gap of knowledge and to substantially contribute to the understanding of the paleoecology of Paleogene and early Neogene hyraxes in their paleocommunities. Within the DFG research unit 771 we have developed a software for virtual reconstruction of the mastication of extinct mammals and to study the efficiency of dental function based on quantitative data. The Occlusal Fingerprint Analyzer (OFA) has been successfully used for reconstructing the masticatory cycle of various mammalian groups and shall be applied to hyrax dentitions. Aim of the proposal is to gain detailed insight into hyrax mastication and to evaluate their efficiency. Efficiency estimation will be performed via a quantification of the contact areas of the occlusal surface that are involved during the chewing cycle. The data obtained from hyraxes will be compared with data from rhino dentitions for evaluating differences of efficiency between both groups. We expect from the project in-depth insight into the evolution of the function of mammalian dentitions, of dietary preferences of extinct hyraxes, their ecological role within the mammalian paleocommunities, and their decline in diversity during the Neogene and replacement by hoofed mammals.