The males and females of all swallowtail angels differ in color, but in this case, the difference is so extreme that the male was given the species’ scientific name in 1934, while the female was described as “Holacanthus fuscosus” in 1970. Only aquarium observations confirmed they were the same species. In Japan, this species is found only in Okinawa and “The Seven Islands of Izu” (of which there are actually around a dozen). It is also found off Taiwan and the Philippines.