Sundadanio atomus Conway, Kottelat & Tan, 2011

Family:  Sundadanionidae (Tiny danios)
Max. size:  1.57 cm SL (male/unsexed)
Environment:  benthopelagic; freshwater
Distribution:  Asia: peat swamp forests of Pulau Singkep, Sumatra, Indonesia.
Diagnosis:  Anal soft rays: 9-10; Vertebrae: 34-35. Distinguished from all its congeners, except Sundadanio axelrodiand Sundadanio goblinus, by having weakly developed dark lateral stripe. Differs from Sundadanio axelrodi by its caudal peduncle with a complete covering of overlapping scales (vs. caudal peduncle devoid of scales or with few small, widely spaced scales situated along horizontal septum) and from Sundadanio goblinus by the absence (vs. presence) of intense dusky markings on the dorsal and caudal fins. Can be further diagnosed by the following combination of characters: small adult body size (largest specimen examined 15.7 mm SL); blue to emerald green sheen (this depends on angle of incident light and perception) across dorsal body surface and an intense red colour across anterior portion of anal fin in live males; absence of secondary lateral stripe in males; absence of reticulate pattern along dorsal body surface; scales posterior to window in body musculature and anterior to anal-fin origin with a single small tubercle at center (Ref. 88800).
Biology:  Inhabits peat swamp forests (Ref. 88800).
IUCN Red List Status: Endangered (EN); Date assessed: 28 January 2019 (B1ab(i,ii,iii)+2ab(i,ii,iii)) Ref. (126983)
Threat to humans:  harmless

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