Morphoogical study of the dietary adaptation of Miocene hominoids

自80年代以来，日本研究人员在肯尼亚北方图尔卡纳湖以南100公里的Nachola和Samburu丘陵地区发现了许多中新世人科动物的牙齿化石。本计画的目的是借由牙齿化石的形态分析来评估这些中新世人科动物的饮食适应。首先，我们通过收集和整理以前发表的文献，定量分析了现存灵长类动物的饮食适应。其次，我们使用新引进的三维数字化和测量系统，精确记录这些灵长类动物牙齿的外部形态。第三，我们综合了有关饮食菜单和牙齿形态特征的数据。第四，我们应用获得的相关性解释的牙齿形态的中新世人科和其他化石人科/人科。除了现存灵长类动物饮食专门化的旧档案，今年我们收集了新的数据，特别强调非洲和亚洲猿。此外，我们还测量了现存灵长类动物，包括黑猩猩，倭黑猩猩（=侏儒黑猩猩），大猩猩，猩猩，长臂猿，狒狒，红疣猴，日本猕猴，cebids。灵长类化石材料有中中新世东非的肯尼亚古猿和尼安扎古猿、原执政猴等。来自东非早中新世的阿法南方古猿和来自莱托利的阿法南方古猿等上更新世人科化石。首先，东非早中新世人科动物，如普罗康索（Proconsul），特征性地显示出高冠尖，这表明他们的饮食偏好是中等坚韧纤维的食物。第二，中中新世肯尼亚古猿，相比之下，有圆形和低的尖，这表明更多的依赖硬坚果和树皮。第三，澳大利亚古猿表现出更多的研磨适应牙齿形态，这表明饮食菜单上有更多的独立性，如硬坚果，谷物和树皮。

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.