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

本项目2002至2004年的成果摘要如下。(1)从安徽省出土的丰富的兔类化石中，中国可以划分为该属的三个连续种(从中新世晚期到上新世晚期)，这些种和现存的Amami兔形成了一个明显的进化谱系。(2)在这三个物种中，最古老的物种被国外合作研究员金(2004)描述为淮南Pliopentalagus，另外两个物种的描述论文正在由Tomida编写。(3)根据上述(1)所述的系统发育关系，对Nhewanopentalagus的系统发育地位提出了质疑，并明确了其属名应改为Trischizolagus属。该报描述了这一变化，目前正在报道中。(4)北美洲的Aztlanolagus属是中国的一个原始种的直系后代，大约在5~6 Ma左右从亚洲迁徙到北美。(5)Aztlanolagus Agilis与中国Pliopentalagus spp.非常相似，尤其是淮南Pliopentalagus，应更名为Pliopentalagus。富田正在准备一份描述上述(4)和这一通用变化的手稿。(6)与最新的Leporidae科分子系统学研究相比，Matthee等人(2004)给出的Pliopentalagus-Pentalagus谱系的分化年龄为9~10 Ma，与中国化石记录估计的7 Ma以上的年龄较为接近。(7)在今后的研究中，计划将面颊牙齿的详细研究扩展到p3具有全部5个内收角的所有其他属(现存的4个，灭绝的1个)，建立包括现存和灭绝的更大规模的系统发育树，并与分子系统学的最新结果进行比较。

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.