HISTORICAL RESUMÉ
Because of the taxonomic confusion that has surrounded the generic name Osteocephalus and two of the species (and their synonyms), we present a brief resumé of the taxonomic history of the group.
Among the amphibians sent to the Muséum National d'Histoire Naturelle in Paris by a Monsieur Leprieur in French Guiana was a single female specimen of a moderately large hylid having a well-ossified skull and smooth dorsal skin. This specimen escaped from the covetous eyes of Johann Tschudi, who prematurely named several species on the basis of specimens in Paris, and survived without an epithet until Duméril and Bibron (1841) proposed for it the name Hyla leprieurii. The description of the species is fairly detailed, but the specimen was not illustrated. This is the earliest trivial name now associated with Osteocephalus.
Fitzinger (1843) in his generic synopsis of amphibians and reptiles proposed the generic name Osteocephalus but did not associate a specific name with the genus. Consequently, Osteocephalus Fitzinger, 1843, is a nomen nudum. Franz Steindachner followed Leopoldo Fitzinger at the Naturhistorisches Museum in Vienna, where he had access to Fitzinger's notes and, of course, the important collections housed in that museum. Steindachner (1862) named two species of Osteocephalus on the basis of Brasilian specimens collected by Johann Natterer. Both species were named in the same publication; O. taurinus appeared on page 77, and O. favolineatus, on p. 80. This is the earliest association of the generic name Osteocephalus with a specific name and a description, both of which satisfy the Code of Zoological Nomenclature for generic availability. Therefore, Steindachner is the authority for the generic name Osteocephalus, which has O. taurinus as the type species by original designation. It is not possible to determine whether or not Steindachner's usage of Osteocephalus was the same as that intended by Fitzinger 19 years earlier.
Steindachner (1862) gave reasonably good descriptions of his two new species and provided excellent illustrations of the two specimens, both large females. Apparently impressed by the similarities between Trachycephalus nigromaculatus Tschudi, 1838, and Osteocephalus taurinus, Steindachner (1867) used the combination Trachycephalus (Osteocephalus) taurinus. This ambiguous usage for the 1860's precludes our determining if Steindachner was in effect synonymizing Osteocephalus with Trachycephalus or whether he was placing Osteocephalus in a subgeneric status. Steindachner (1867) did not mention O. flavolineatus; perhaps by that time he had concluded that flavolineatus was only a color morph of taurinus.
Cope (1867) placed Hyla leprieurii in the genus Hypsiboas Wagler, 1830. Cope (1874) named Osteocephalus planiceps from Nauta, Perú. The single specimen was among the collections made by the Orton Expedition to the upper Amazon Basin and was deposited in the Academy of Natural Sciences in Philadelphia.
Boulenger (1882) placed both Osteocephalus and Trachycephalus in the synonymy of Hyla; he recognized Hyla taurina (with O. flavolineatus as a synonym), H. leprieurii, and H. planiceps. In the same publication Boulenger named Hyla buckleyi on the basis of 10 specimens in the British Museum from Ecuador; in the description he stated that buckleyi was like leprieurii and taurinus in having paired lateral vocal sacs. Boulenger held a lasting influence on taxonomic herpetology, and his generic synonymy of Osteocephalus was unchallenged until only a decade ago.
Goin (1961) presented a generic synopsis of the genera of hylid frogs, in which he recognized Osteocephalus and stated: "There are perhaps eight or ten species of this genus in South America. Certainly taurinus, britti, leprieuri, buckleyi and pearsoni belong here. O. planiceps is surely a synonym of leprieuri and I believe that garbei is as well. The status of such forms as macrotis, riopastazae, and depressa has not yet been settled." Goin defined Osteocephalus as follows: "Males with paired vocal pouches, one at each angle of the jaw; derm of head not co-ossified with skull but roof of skull exostosed." Trueb (1970a) elaborated on Goin's definition and assuredly included only O. taurinus and O. leprieurii in the genus.
Goin's inclusion of buckleyi, britti, and pearsoni in Osteocephalus was the first association of any of these names with that genus. Duellman (1970a) demonstrated that Garbeana garbei Miranda-Ribeiro, 1926, was a member of the Hyla rubra group. Hyla macrotis Andersson, 1945, is a Phrynohyas. Trueb and Duellman (1970) determined that Hyla verrucigera Werner, 1901, is the earliest name for an Osteocephalus displaying striking sexual dimorphism in coloration and texture of the dorsal skin; Hyla riopastazae Andersson, 1945 (female holotype), and Hyla orcesi Funkhouser, 1956 (male holotype), were placed in the synonymy of Osteocephalus verrucigerus.
Hyla pearsoni Gaige, 1929, is a small species of Osteocephalus. Our findings substantiate Goin's suggestions relative to two other taxa. Hyla leprieurii britti Melin, 1941, from the Rio Uaupés, Brasil, and Hyla depressa Andersson, 1945, from the Río Pastaza watershed, Ecuador, are members of the genus Osteocephalus, but both are synonyms of earlier names—leprieurii and taurinus, respectively. Another name proposed by Melin (1941), Hyla (Trachycephalus) vilarsi from Taracuá, Brasil, also is placed in the synonymy of O. taurinus.