Danio annulosus is a species of Chain danio fish in the family Cyprinidae in Danio genus. The species is named and described jointly by Sven O Kullander, M.D Mizanur Rahman, Michael Noren and Abdur Rob Mollah in 2015 in association with the Department of Zoology, Swedish Museum of Natural History, Sweden and the Department of Zoology, University of Dhaka, Bangladesh. The study and paper on Danio annulosus was published in ZooTaxa both online and in print in the same year (2015). It was collected from a small pool at the bottom of the Shuvolong Falls in the Kaptai Lake system in Rangamati district in the Chittagong division, Bangladesh. The species name annulosus is derived from the neo-Latin word meaning "ringed", from the color pattern on the side of the fish which resembles a pattern of dark rings.

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