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CGC-01 General contributions to climate change
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Late Miocene paleoenvironmental change of hominoid sites in Kenya -mesowear analysis of Hipparion cheek teeth
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Hideo Nakaya, Kagoshima University (Japan)
Yutaka Kunimatusu, Kyoto University (Japan)
Masato Nakatsukasa, Kyoto University (Japan)
Haruo Saegusa, University of Hyogo (Japan)
Akira Fukuchi, Kagoshima University (Japan)
Kevin Uno, University of Utah (United States)
Hiroshi Tsujikawa, Tohoku University (Japan)
Tetsuya Sakai, Shimane University (Japan)
Yoshihiro Sawada, Shimane University (Japan)
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The tooth mesowear method to equids is a new approach of reconstructing ungulate diets and its paleoenvironments. We analyzed mesowear of Hipparion cheek teeth from the Late Miocene Namurungule and Nakali Formations from Northern Kenya. The distance of the both sites is fifty or sixty kilometers. Only one taxon of fossil hominoid "Samburupithecus kiptalami" was found from the Namurungule Formation. On the other hand, a hominoid "Nakalipithecus nakayamai" and several other catarrhine taxa were found from the Nakali Formation. The geological ages of the both formations are similar. We analyzed the difference of paleoenvironments of both formations by mesowear method to Hipparion cheek teeth from the Namurungule and Nakali Formations. The occlusal relief of teeth is scored "high: or "low", the cusp shape is classified as "sharp", "round" and "blunt".
In the occlusal relief of Hipparion teeth, more than half of the teeth from the Namurungule Formation were scored "high", almost all the teeth from the Nakali Formation were scored "low". In the cusp shape, the teeth from the both formations were classified as "round" to the top. Many of the teeth from the Namurungule Formation were classified as "blunt", but none of them as "sharp". The teeth from the Nakali Formation, however, were classified as "sharp" to the second and very rarely as "blunt".
The following conclusions are reached: paleoenvironments of the Nakali Formation (9.9-9.8Ma) may be woodland environments, while those of the Namurungule Formation (9.6Ma) may be openland environments. This environmental difference between the Namurungule Formation and Nakali Formation probably indicates the environmental change through geological age and/or the topographic difference between highland and lowland at the similar age.
Further analyses of sedimentary environments and stable isotope method to the both formations and fossil materials will help reconstruct the paleoenvironments of hominoid sites more intensively.
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