Abstract: The systematic position and phylogeny of extant river dolphins was analyzed based on 307 bp of cyt b gene sequences of Baiji ( Lipotes vexillifer ) and Gangs river dolphin (Platanista gangetica) and of published homologous sequences of other cetaceans. The sequence difference among different genera of river dolphins was similar to or greater than t hose among other odontoceti families. Therefore, these groups of river dolphins should be refered to separate families, i.e. Platanistidae , Lipotidae, Iniidae , and Pontoporiidae. The phylogenetic analysis supported the following relationship of river dolphins and Delphinoidea : ( Platanistidae ( (Lipotidae ( Iniidae , Pontoporiidae) ) Delphinoidea) ). Among the four river dolphin families, the Platanistidae was the earliest divergent clade, the Lipotidae was the next, and then the Iniidae and Pontoporiidae. The cl ade Lipotidae + Iniidae and Pontoporiidae was a sister group of the Delphinoidea, and the above three families joined the infraorder Delphinida together with the Delphioidea. No affinity was revealed between the Platanistidae and the other river dolphin families . Therefore, the river dolphins were paraphyletic, and it was reasonable to place Platanista at super family leve l. It was considered that it would be reasonable to refer Lipotes as a cl de of super family level. The difference between cyt b sequence of Ganges river dolphin and Indus river dolphin was very small, which supported that Ganges river dolphin and Indus river dolphin ( P. minor ) were probably two subspecies of a single species.

Key words: River dolphins, Cyt b gene, Molecular phylogeny

摘要： 测定了白暨豚和恒河豚细胞色素b 基因307 bp的DNA 序列,并与其它鲸类的相应序列合并, 分析了淡水豚类(恒河豚、印河豚、白暨豚、亚河豚和弗西豚) 的系统学位置和系统发生。淡水豚类不同属间的序列差异已达到或超过了其它齿鲸类科间的差异水平,因此它们分别归属于不同的科, 即恒河豚科、白暨豚科、亚河豚科和弗西豚科。系统发生分析支持淡
水豚类和海豚类之间具有下述的关系: (恒河豚科( (白暨豚科(亚河豚科, 弗西豚科) ) 海
豚总科) )。即淡水豚的4 个科中, 恒河豚科是最早分化的一支, 其次是白暨豚科, 然后是亚河豚科和弗西豚科的分化。白暨豚科和亚河豚科+ 弗西豚科组成海豚总科的姊妹群, 并与海豚总科一同组成海豚下目。恒河豚与其它淡水豚类间无直接的亲缘关系。淡水豚类是并系
的。把恒河豚类独立为恒河豚总科是合理的。初步认为有理由把白暨豚类也作为一个总科级
的支系。恒河豚和印河豚间的序列差异极小, 两者可能只是同一个种的2个亚种。

关键词: 淡水豚类, 细胞色素b 基因, 分子系统发生