Comprehensive DescriptionRead full entry
In males, the snout-vent length ranges from 14.8-18.3 mm, while in females the range is 15.8-19.8 mm. The heads are slightly wider in males than females, while females are larger overall in size. The snout is blunt and broadly rounded in dorsal view, but acutely rounded when viewed laterally, and extends past the lower jaw. The tympanum is round, and partly concealed posterodorsally. Fingers decrease in length from III>I>II>IV; the third finger is not swollen in males. The forearm is slightly longer than the upper arm, and lacks an ulnar fold. The palmar tubercle is nearly round and the thenar tubercle is elliptical, and approximately one-third the diameter of the palmar tubercle. All fingers have expanded discs and no fringes. Hands lack webbing, although basal webbing is present on the feet between toes II-IV. The dorsum is granular, with granulation increasing toward the posterior (Lima et al. 2009).
Color of the dorsum varies from light grayish brown to orange brown, often with one to several dark brown hourglass, triangular, or diamond-shaped markings. Dorsal surfaces of the arm are light orange-brown, while dorsal surfaces of the legs are light gray. Thighs, shanks, and feet have dark brown crossbars. Males have green-yellow throats with a yellow chest and belly and melanophores on the gular sac, while females have white throats with a yellow outer edge, and white chests and bellies. No dorsolateral stripes are present. A diffuse pale tan to orangish-brown oblique lateral stripe is present, running from the midbody (sometimes starting as far forward as the arm insertion) to the groin. A ventrolateral stripe of irregular white spots runs from the anterior corner of the eye to the groin. The pupillary ring and upper iris are metallic gold with a fine black network, and the rest of the iris is brown.
Tadpole bodies are ellipsoid when viewed dorsally and flattened when viewed laterally. Larval snouts have small dorsolateral nostrils, and are bluntly rounded in both dorsal and lateral view. The spiracle is sinistral, directed dorsolaterally, located at midbody below the lateral midline, and is free. The vent is attached to the ventral fin. The upper tailfin starts at the junction of the body and tail, and the tail has robust caudal musculature. Emarginate, anteroventral oral disc, with papillae on lateral margin of anterior labium and surrounding posterior labium. Lower jaw sheath is V-shaped and both upper and lower jaw sheaths are serrated. LTRF 2(2)/3(1) (Lima et al. 2009).
Tadpoles are grayish-brown with irregular brown and silver blotches. Tadpoles of Allobates brunneus are easily distinguishable from those of the related species (A. marchesianus and A. caeruleodactylus) by the regular arrangement of papillae on the oral disc margin and irregular spots on the tail for A. brunneus (vs. unusual papillae distribution and distinct irregular stripes for the others). The oral disc of the A. brunneus tadpole has fewer surrounding papillae than that of A. subfolionidificans. The tadpole of A. nidicola has a reduced oral disc, lacks both spiracle and vent, and has yolk-filled intestines, so is easy to distinguish from that of A. brunneus. Not all Allobates tadpoles have been described (Lima et al. 2009).