South Asian river dolphins (Platanista gangetica) are among the most endangered of the world's cetaceans. The two subspecies in the family Platanistidae, Indus, and Ganges river dolphins (P. g. minor and P. g. gangetica), are both threatened by dams and barrages, declining river flows, fisheries bycatch, and pollution. We examine differences in external and skull morphology between dolphins in each river system to clarify their taxonomic status. Skulls from each river system could easily be differentiated using diagnostic differences in the shape of the frontal bones behind the nasals. This feature was present in all individuals irrespective of size, age, and sex. Ganges river dolphins are sexually dimorphic with females larger than males, but there was no evidence of dimorphism in the small sample of Indus river dolphins. There were no mitochondrial DNA haplotypes shared between the two river systems, and five fixed differences suggested a long-term (approximately 0.55 million years) absence of gene flow. Diagnosable differences in morphological and genetic characteristics indicate long-term reproductive as well as geographic isolation of Indus and Ganges river dolphins. We conclude that Indus and Ganges river dolphins should each be recognized as distinct species, and elevate the Indus subspecies, Platanista gangetica minor, to species level, Platanista minor Owen, 1853. Formal redescriptions are provided for both species.

中文翻译：

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南亚河豚（Platanista）的分类修订：印度河豚和恒河豚是不同的物种

南亚河豚( Platanista gangetica ) 是世界上最濒危的鲸类之一。海豚科、印度河和恒河豚的两个亚种（P. g. minor和P. g. gangetica)，都受到水坝和拦河坝、河流流量下降、渔业兼捕和污染的威胁。我们研究了每个河流系统中海豚的外部和头骨形态的差异，以阐明它们的分类地位。使用鼻骨后面额骨形状的诊断差异可以很容易地区分来自每个河流系统的头骨。无论大小、年龄和性别，所有个体都存在此特征。恒河豚是雌性比雄性大的雌性二态性，但在印度河海豚的小样本中没有证据表明存在性二态性。两个河流系统之间没有共享的线粒体 DNA 单倍型，五个固定差异表明长期（约 55 万年）缺乏基因流动。形态和遗传特征的可诊断差异表明印度河和恒河豚的长期繁殖以及地理隔离。我们得出的结论是，印度河和恒河豚都应该被视为不同的物种，并提升印度河亚种的地位，Platanista gangetica minor，物种层面，Platanista minor Owen，1853 年。为这两个物种提供了正式的重新描述。