The chromosome number of Hynobius fucus was found by Lai and Lue (2008) to be 2n = 58, displaying a karyomorph similar to those previously reported in stream-type salamanders from Taiwan. Based not only on cytogenetic features but also on developmental characteristics such as the embryonic stage and the presence of interdigital membranes during limb formation this species can be confidently classified as a lotic stream-type salamander. Morescalchi (1975) proposed that karyotype evolution in families of urodeles tends to proceed from higher to lower chromosome numbers. Our findings from Taiwan suggest karyotype evolution within the genus Hynobius , that is, the chromosome number of this species may have increased from 2n = 56 in the pond-type ancestor to 2n = 58 in this stream-type lineage.