Of the four genera, _Osteocephalus_ is the most generalized in morphology, and, like _Phrynohyas_, has no specialized habits. _Osteocephalus_ and _Argenteohyla_ are similarly distinguished from _Phrynohyas_ and _Trachycephalus_ on the basis of vocal sac structure. The vocal sacs of _Osteocephalus_ and _Argenteohyla_ are posterior and protrude posterolateral to the angles of the jaws when they are inflated, whereas those of _Phrynohyas_ and _Trachycephalus_ are more lateral and protrude posterior to the angles of the jaws when inflated.
Although _Osteocephalus_ and _Argenteohyla_ have similar vocal sac structure, they are obviously distinct. The monotypic _Argenteohyla_ is a rather specialized, semifossorial frog (Trueb, 1970b), characterized by smooth skin, moderate-sized digital discs, and a large inner metatarsal tubercle. The general architecture of the skull is not unlike that of _Osteocephalus_; the skulls of both are well roofed, broader than long, and characterized by posterolaterally oriented parasphenoid alae. _Argenteohyla_ bears small, slightly curved prevomerine dentigerous processes in contrast to the large, angular processes of _Osteocephalus_. The skull of _Argenteohyla_ shows specializations, apparently adaptations to its semifossorial mode of existence, which further distinguish the genus from _Osteocephalus_. In comparison with _Osteocephalus_, the cranium of _Argenteohyla_ is slightly depressed anteriorly, the roofing bones extensively casqued, and the palatines robust.
Osteologically, _Osteocephalus_ more closely resembles _Phrynohyas_ than either of the other two genera, but _Osteocephalus_ and _Phrynohyas_ are clearly distinct on the basis of their respective vocal sac structure. Like _Osteocephalus_, skulls of the members of the genus _Phrynohyas_ are broader than long, have extensive dermal roofing bones, and have posterolaterally oriented parasphenoid alae. In contrast to _Osteocephalus_, the dentigerous processes of the prevomers are curved, rather than angular in _Phrynohyas_. Furthermore, the latter genus is singularly distinguished from _Osteocephalus_, _Argenteohyla_, and _Trachycephalus_ by having extensively developed parotoid glands that produce a viscous, milky volatile secretion.