Abstract
We describe a new species of Allobates from the south of eastern Amazonia, Brazil. This species inhabits fluvial springs and the banks of small streams in terra-firme forests along the Tapajós River basin. Average snout-to-vent length is 17.78 mm (range 16.09–19.59 mm) among males and 19.50 mm (range 17.97–20.84 mm) among females. Surface of dorsum is marked by a distinct dark color pattern, with three convex areas, triangle and diamond-shaped. The species has a diffuse pale dorsolateral line (absent in some specimens), while the oblique lateral bar is defined. Dark-brown transversal stripes are present on femoral and tibial dorsal surfaces, which align with each other in live specimens when at rest. Tadpoles have short papillae on anterior (8–10 papillae on each side) and posterior labium (>30 papillae). Posterior labium is projected to the front, hiding posterior tooth rows. Eggs are deposited in nests on rolled or cranked dead leaves on the forest floor. Egg membranes and jelly-nests are transparent. Advertisement calls are mainly characterized by the continuous emission of single notes that might shift sporadically to note-pairs, emitted during short periods. Notes are split by regular silent intervals, with peak frequency ranging between 4273–4867 Hz.