Some individuals have a short, pale linear mark running laterally from inguinal region towards the mid section of the body.

A white, iridescent ventrolateral stripe runs along the lower margin of the dark brown flanks, all way from tip of snout to the groin but often interrupted.

The throat, gular, and pectoral regions, as well as the abdomen, are uniformly unpigmented, appearing light gray to translucent.

[2][4] The area of the type locality is a mosaic of seasonally flooded (igapó) and unflooded (terra-firme) primary forests.

After hatching, the tadpoles are carried on the back of the male, or rarely, female, until they are deposited in small temporary pools or moist leaf litter where they continue their development.

[5] The known distribution of Allobates sumtuosus, as now understood, has since expanded and includes many protected areas: Rio Trombetas Biological Reserve (the type locality of Allobates sumtuosus) and several others in Brazil,[4] at least two protected areas in Peru,[1] Mabura Hill Forest Reserve in Guyana (the type locality of Allobates spumaponens[2]), and Sipaliwini Nature Reserve in Suriname.

[3] Its known range also overlaps with several other protected areas, even though it has not been formally reported within their boundaries: Estação Ecológica do Grão Pará, Floresta Nacional de Saracá-Taquera, Floresta do Parú, Reserva Biológica do Rio do Trombetas, Reserva Biológica de Maicurú, Floresta de Faro, and Reserva Florestal Adolpho Ducke.