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''Parictis'' is the earliest genus of bear known.〔While originally classified as a ''bear'' (Ursidae), , others consider the entire Amphicynodontinae family to be at most bear-dogs. 〕 It was a very small and graceful ursid with a skull only 7 cm long. ''Parictis'' first appeared in North America in the Late Eocene (ca. 38 million years ago), but it did not arrive in Eurasia until the Miocene. There is some suggestion that ''Parictis'' may have emigrated from Asia into North America during the major sea level low circa 37 mya, because of the continued evolution of the Amphicynodontinae into the Hemicyoninae in Asia.〔''Several students (Erdbrink 1953, Kurten 1966, Mitchell and Tedford 1973, Thenius 1979) suggested that the evolutionary line between the canid subfamily Amphicynodontinae and the ursid subfamily Hemicyoninae was through the genera Cephalogale and Ursavus.'' 〕 Although no ''Parictis'' fossils have been found in East Asia, ''Parictis'' does appear in Eurasia and Africa but not until the Miocene.〔 ==Species== * ''P. dakotensis'' Clark 1936 37 Million years old * ''P. gilpini'' Clark & Guensburg 1972 35 Million years old * ''P. major'' Clark & Guensburg 1972 * ''P. montanus'' Clark & Guensburg 1972 36 Million years old * ''P. parvus'' Clark & Beerbower, 1967 38 Million years old * ''P. personi'' Chaffee 1954 33 Million years old * ''P. primaevus'', Scott 1893 Although Hall (1931) thought to reassign this species to the Canidae, Hunt (1998) clearly places it within the Ursidae, under ''Parictis''. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Parictis」の詳細全文を読む スポンサード リンク
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