Evolutionary study of Pliopentalagus-Pentalagus lineage based mainly on the Chinese fossil records.

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Results of the present project from 2002 to 2004 are summarized as follows. (1)Abundant rabbit fossils of Pliopentalagus that were excavated from Anhui Province, China can be classified into three successive species (from the latest Miocene to late Pliocene) of the genus, and these species and extant Amami rabbit (Pentalagus furnessi) form a clear example of the evolutionary lineages. (2)Among those three, the oldest species was described as Pliopentalagus huainanensis by Jin (2004) who is a foreign co-operative researcher, and a descriptive paper of two other species are being prepared by Tomida. (3)Based on the phylogeny mentioned in (1)above, phylogenetic position of Pliopentalagus nihewanensis was questioned, and it became clear that its generic assignment should be changed to the genus Trischizolagus. The paper described this change is now in press. (4)It became clear that North American genus Aztlanolagus is a direct descendant of a primitive species of Chinese Pliopentalagus (P.huainanensis or closely related species), and its migration from Asia to North America occurred at about 5 or 6 Ma. (5)Aztlanolagus agilis is very similar to Chinese Pliopentalagus spp., especially P.huainanensis, and so the genus should be changed to Pliopentalagus. A manuscript describing (4)above and this generic change is being prepared by Tomida. (6)Comparing with the most recent study of molecular phylogeny of the family Leporidae, Matthee et al.(2004) gave an age of 9 to 10 MA for the diverging time of Pliopentalagus-Pentalagus lineage, which is rather closer to the age of over 7 MA estimated from the Chinese fossil records. (7)In future studies, it is planed to expand the detailed studies on the cheek teeth to all other genera (4 extant and 1 extinct) who's p3 has all 5 reentrant angles, to establish a larger scale phylogenetic tree including both extant and extinct taxa, and to compare them with the newest results of molecular phylogeny.