William Edward Duellman

“ Ontogenetic change in coloration is slight or non-existent in buckleyi, pearsoni, and taurinus, except that juveniles lack ventral markings. A dark blotch on the back and distinct transverse bars on the limbs are evident in juveniles of verrucigerus; these markings are obscured in the adults. Juveniles of leprieurii are olive-brown with yellow dorsolateral stripes; the transverse dark marks, characteristic of the adults, appear before the stripes are lost. ”

“ We have examined 893 preserved frogs, including the type specimens of all included nominal taxa, 8 skeletons, 1 lot of eggs, and 3 lots of tadpoles that we refer to the genus Osteocephalus; in addition skulls were removed from five preserved specimens, and radiographs were made of 12 other preserved specimens. We have been fortunate in seeing living individuals of all species, except O. pearsoni, but we have colored photographs of a living specimen of that species. Figures 1 and 2 were drawn from projected colored transparencies of living frogs. ”

“ Osteocephalus buckleyi is further distinguished by the presence of narrow transverse processes on presacrals five through eight (Fig. 7b) ; males have narrower processes than do females. The processes are moderately wide but subequal in width in pearsoni, taurinus, and verrucigerus, whereas they are nearly equivalent in width to one another and to the sacral diapophyses in leprieurii (Fig. 7a) . The sacral diapophyses of all species are moderately dilated and posterolaterally inclined. The coccyx bears a distinct dorsal ridge and has a bicondylar articulation with the sacrum. ”

“ Most juveniles (less than 40 mm in snout-vent length) can be identified readily. There is a tendency for the dorsal markings of juveniles to consist of several small spots. Apparently with growth the spots usually coalesce, forming a large median blotch, but some adults retain the juvenile pattern. Cochran and Goin (1970:251) erroneously identified several juveniles from Colombia as Hyla palpebrogranulata Andersson. ”

“ Skin.—The dorsal skin of all males of Osteocephalus is tuberculate to varying degrees, whereas the dorsal skin of females is smooth, or nearly so (Fig. 4) . Osteocephalus verrucigerus differs from other members of the genus by the presence of numerous, large tubercles bearing keratinized tips. ”

“ The coloration remains much the same as described by Cope, who provided no means of distinguishing planiceps from taurinus. The coloration and morphometric and structural characters of the type of planiceps all fall within the range of variation displayed by series of O. taurinus from the upper Amazon Basin. ”

“ Osteocephalus leprieurii.—Males were heard calling sporadically at Puerto Libre in July 1968, and at Santa Cecilia in May 1969. A small chorus was found on the night of 12 May 1969 at Lago Agrio, where the frogs were perched on branches of fallen trees over a temporary pool. The call is a soft rattling chuckle. In late April and May many gravid females and males with well-developed nuptial excrescences were obtained from trees as they were felled at Lago Agrio. The reproductive condition of the frogs indicates that they probably breed in May. ”

“ In the latter species marginal portions of the frontoparietals, the dorsal surfaces of the nasals, and the posteromedial part of the exposed sphenethmoid are slightly exostosed, resulting in an open, reticulate pattern of dermal sculpturing of exceedingly low relief (Fig. 6c) . Osteocephalus taurinus is characterized by casquing, co-ossification, and a rather intricate pattern of dermal sculpturing, which was described in detail and illustrated by Trueb (1970a) . ”

“ Throughout the rainy months that we have worked in Ecuador (April-August) we have found occasional individuals perched on bushes or low trees at night. Large numbers of adults were observed only during a clearing operation which resulted in the felling of many large trees. Thus, it seems likely that leprieurii is a tree-top inhabitant. A partially digested adult male was removed from the stomach of a Hemiphractus proboscideus.
At Santa Cecilia many recently metamorphosed young and juveniles were found in June and July 1968. ”

“ Trachycephalus is the most readily identifiable of the four genera under discussion. Members of this genus are large frogs with heavily casqued and co-ossified skulls (Trueb, 1970a) . The dermal roofing bones bear ornate and characteristic patterns of sculpturing. The medial ramus of the pterygoid does not articulate with the otic capsule, and the parasphenoid alae are laterally, rather than posterolaterally, oriented. A dermal sphenethmoid is present, and the parasphenoid bears odontoids. The basic structure of the skull has many characters in common with both Osteocephalus and Phrynohyas. ”

“ Mean values of snout-vent lengths of males from other localities are: Río Pastaza drainage, Ecuador 73.8 mm, Surinam 67.7 mm, Río Ucayali drainage, Perú 57.6 mm, and Guyana 55.5 mm. Although the difference between the smallest and largest adults is highly significant, populations bridging the gap do exist. Furthermore, the geographic arrangement of small versus large frogs is a confusing mosaic. ”

“ Snout-vent lengths of 18 specimens are 12.3-17.0 (mean 15.1) mm. The smaller frogs were recently metamorphosed as evidenced by the melanophore deposits above the vent. The coloration of the young is strikingly different from that of the adults (see account of O. leprieurii) , so the association of the young and adults was not made until individuals with intermediate patterns were obtained at Lago Agrio in May 1969. Probably juveniles obtained in June and July are the offspring of an April or May breeding. ”

“ Tadpoles and mating calls are available for only one species, O. verrucigerus (Trueb and Duellman, 1970) ; these and other important systematic characters, such as karyotypes, are not available for the group at this time. ”

“ 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. ”

“ Melin (1941:42) described the coloration of the holotype as follows: "Above uniform reddish brown; upper eyelids and sides of head darkish brown; below the rostral edge a narrow dark band, continuing as a broader light-edged one through the eye and tympanum towards the base of the forelimb and then farther on continuing along the sides as a line of black spots; sides of upper jaw whitish with traces of dark cross bars (one distinct under the eye) ; sides of body darkish with black spots and marble, often on a whitish ground ”

“ Distribution of Osteocephalus taurinus.
Remarks.—This widespread species is highly variable in size and coloration. Striking differences in snout-vent length are evident in series from various parts of the range. The smallest calling males (CAS-SU 12351-6 from Rio Tapirapé, Brasil) have snout-vent lengths of 46.5-60.3 (mean 53.3) mm, whereas the largest (FMNH 140254, KU 92243-6, WCAB 9997, 10001, 10003-4 from Igarapé Marmelo, Brasil) have snout-vent lengths of 71.5-84.6 (mean 77.6) mm. ”

“ Our tendency has been to take a conservative view of species; thus it is doubtful that any subsequent worker will recognize fewer species in the genus. Our observations on these frogs in Amazonian Ecuador are presented in a final section of this paper. ”

“ Institutional libraries interested in exchanging publications may obtain the Occasional Papers and Miscellaneous Publications by addressing the Exchange Librarian, University of Kansas Library, Lawrence, Kansas 66044. Individuals may purchase separate numbers of all series. ”

“ Osteocephalus taurinus.—A small chorus occurred at Lago Agrio [Pg 42] on 12 May 1969. Males were calling from the ground adjacent to a small pool amidst recently felled trees. The males were very wary and, when approached, jumped onto limbs and ran up branches ”