Taxonomy and molecular phylogeny of freshwater gobies of genus, Rhinogobius from Laos and Thailand with comment on the unusual gene duplication of mitochondrial genome I-Shiung Chen*, Maurice Kottelat and Ping-Hwa Liu 國立海洋生物博物館 The gobiid genus Rhinogobius is widely-distributed around the West Pacific. The species occurring in the freshwaters of Laos and Thailand including 4 species new to science. A preliminary survey of molecular phylogeny of some purely freshwater taxa shows that they belong to the same calde as non-diadromous Chinese species with similar life history. The very unusual phenomenon as gene duplication in mitochondrial genome is reported here for the first time from fish sequences. The possible occurrence of replication models is discussed.