Melanophryniscus atroluteus is a species of toad in the family Bufonidae. It is found in northeastern Argentina, Uruguay, southern Paraguay, and southern Brazil (Rio Grande do Sul, presumably also Santa Catarina). While in the past it was considered a subspecies of Melanophryniscus stelzneri, it might rather be conspecific with Melanophryniscus montevidensis. Common name Uruguay redbelly toad (also spelled Uruguay red belly toad) has been coined for it.
Males can reach 25 mm (1.0 in) and females 29 mm (1.1 in) in snout–vent length, although reported lengths are commonly slightly smaller. Skin is strongly granular. The dorsum is uniformly black, without blotches, while the belly is black and has red and/or yellow blotches. The throat is dark. Webbing is poorly developed.
When threatened, this species exhibits the Unkenreflex behavior.
