Sundadanio margarition Conway, Kottelat & Tan 2011

Distinguished from all congeners by the following combination of characters: large adult size (largest specimen examined 19.7 mm SL); live males with emerald blue-green sheen present across dorsal body surface and an intense black-red marking across anterior portion of anal fin; preserved males with a well developed dark lateral stripe of roughly uniform depth along entire length, horizontal through ventral border of which, when brought forward, extendingthrough dorsal half of eye; presence of a weak secondary lateral stripe of small melanophoresrunning parallel to dark lateral stripe along its ventral margin from posterior to opercularopening to point opposite middle of anal fin; secondary lateral stripe of males not visible inlive specimens; absence of reticulate pattern over dorsal body surface; absence of dusky markings on distal tips of dorsal and caudal fins; presence of enlarged scales next to window in body musculature; scales posterior to enlarged scales next to window in body musculature and anterior to anal-fin origin with a single small tubercle at center; complete covering of scales on caudal peduncle (Ref. 88800).Description: Dorsal-fin rays ii.6.i; anal-fin rays iii.6; pectoral-fin rays i.6-7.i-ii; pelvic-fin rays i.5.i (Ref. 88800).

Dorsal soft rays (total): 9; Analsoft rays: 9; Vertebrae: 34

Inhabits swamp forests and blackwater streams (Ref. 88800).

Sundadanio margarition is a danionin in the family Cyprinidae. It is endemic to Sarawak, Malaysian Borneo, and known from the Rajang and Sarawak River drainages. It lives in coastal peat swamp forests.

Sundadanio margarition reaches a maximum size of 1.9 cm (0.75 in) standard length.