The belly and tips of digits were white; the vocal sac was purplish brown, and the iris was dark grayish gold.
The venter is white, and the vocal sac in breeding males is yellow.
The vocal sac structure of Trachycephalus is like that of Phrynohyas and therefore further distinguishes it from Osteocephalus.
The venters are gray or white, and the vocal sac is nearly black in some species.
The vocal sac was brownish gray; the iris was a bright golden color.
The ventral surfaces, including the vocal sac, are white; the iris is golden and flecked with black.
It is only the males that possess the vocal sac, so that the toad chorus is composed solely of male voices.
The vocal sac in breeding males is quite evident; it is single, median, and when expanded, spherical.
Osteocephalus and Argenteohyla are similarly distinguished from Phrynohyas and Trachycephalus on the basis of vocal sac structure.
The openings into the vocal sac are narrow slits along the inner posterior border of the jaw rami.