Morphoogical study of the dietary adaptation of Miocene hominoids

点击翻译按钮获取中文摘要

From the Nachola and Samburu Hills regions, 100 km south of Lake Turkana, northern Kenya, many fossil teeth of Miocene hominoids were discovered by Japanese researchers since 80ls. The aim of this project is to estimate dietary adaptations of these Miocene hominoids by morphological analyzes of the fossils teeth.The research strategy has several steps. First, we analyzed dietary adaptations among living primates quantitatively by collecting and sorting previously published references. Second, we recorded precise external morphology of these primates teeth by using the newly introduced three dimensional digitizing and measuring system. Third, we synthesized the data about dietary menu and morphological features of tooth. Fourth, we applied obtained correlations to the interpretation of the tooth morphologies of the Miocene hominoids and other fossil hominoids/hominids. In addition to an old archive of the dietary specialization of living primates, this year we collected new data especially emphasizing African and Asian apes. Also, we measured additive new materials of living primates, which include chimpanzees, bonobo (=pygmy chimpanzee), gorilla, orangutan, gibbons, baboons, red colobus, Japanese macaque, cebids. Materials of fossil primates are Kenyapithecus and Nyanzapithecus from Middle Miocene East Africa, Proconsul spp. from Early Miocene East Africa, Australopithecus afarensis from Laetoli and other PlioPleistocene hominids.Major results clarified are as follows. First, East African early Miocene hominoids such as Proconsul characteristically displays high crown cusps, suggesting a dietary preference on food stuff with moderately tough fibers. Second, Middle Miocene Kenyapithecus, in contrast, has round and low cusps, suggesting more dependence on hard nuts and barks. Third, austolaropithecines exhibit more grinding adapted dental morphologies, suggesting a dietary menu with a more independence on hard an tough stuff such as hard nuts, grains and barks.