Part 2

Much of the taxonomic confusion and multiplicity of trivial names is due to the great amount of color variation in taurinus and to the sexual dimorphism in the texture of the dorsal skin in all of the species. The details of variation in these and other characters and our justifications for the synonymies are given in the accounts of the species. All of the trivial names that apply to species herein recognized as members of the genus Osteocephalus are listed in table 1.

=Osteocephalus= Steindachner, 1862

Osteocephalus Steindachner, 1862:77 [Type species.--Osteocephalus taurinus Steindachner, 1862, by original designation]. Not Osteocephalus Fitzinger, 1843:50 (nomen nudum).

Diagnostic Definition.--1) Skull broader than long; 2) dermal roofing bones of skull well ossified, exostosed, and/or co-ossified in some species; 3) prenasal and internasal bones absent; 4) parasphenoid alae posterolaterally oriented; 5) dentigerous processes of prevomers angular (/--\); 6) vocal sacs paired, posterior, and when inflated protruding posteroventral or posterolateral to angles of jaws; 7) submentalis muscle moderate in size and araphic; 8) intermandibularis muscle undifferentiated and bearing an elongate median aponeurosis; 9) parotoid glands absent or poorly developed, skin not producing viscous secretion characteristic of Phrynohyas; 10) skin on dorsum tuberculate in males, smooth in females; 11) tympanum large, 60 percent or more of diameter of eye; 12) fingers about one-third, toes more than three-fourths webbed; 13) discs large, round; 14) nuptial excrescences present in breeding males; 15) inner metatarsal tubercle not modified for digging; 16) outer metatarsal tubercle absent; 17) tarsal fold weak or absent; 18) pupil horizontal; 19) palpebrum clear; 20) known tadpoles having two upper and five lower rows of teeth.

TABLE 1.--Alphabetical Synonymy of the Species of Osteocephalus.

Trivial Name, Original Generic Name, Author, Date Current Name ---------------------------------------------------------------------- britti (Hyla leprieurii) Melin, 1941 O. leprieurii buckleyi (Hyla) Boulenger, 1882 O. buckleyi cabrerai (Hyla) Cochran and Goin, 1970 O. buckleyi carri (Hyla) Cochran and Goin, 1970 O. buckleyi depressa (Hyla) Andersson, 1945 O. taurinus festae (Hyla) Peracca, 1904 O. buckleyi flavolineatus (Osteocephalus) Steindachner, 1862 O. taurinus leprieurii (Hyla) Dumeril and Bibron, 1841 O. leprieurii orcesi (Hyla) Funkhouser, 1956 O. verrucigerus pearsoni (Hyla) Gaige, 1929 O. pearsoni planiceps (Osteocephalus) Cope, 1874 O. taurinus riopastazae (Hyla) Andersson, 1945 O. verrucigerus taurinus (Osteocephalus) Steindachner, 1862 O. taurinus verrucigera (Hyla) Werner, 1901 O. verrucigerus vilarsi (Hyla) Melin, 1941 O. taurinus

Content.--As defined here, the genus contains five known species: O. buckleyi (Boulenger), O. leprieurii (Dumeril and Bibron), O. pearsoni (Gaige), O. taurinus Steindachner, and O. verrucigerus (Werner).

Distribution.--The Guianas and Amazon Basin; also in the upper Orinoco and Magdalena drainages. Most localities are at elevations below 500 m, but the genus ascends the Amazonian slopes of the Andes to elevations of about 1800 m.

ANALYSIS OF CHARACTERS

Size and Proportions.--Frogs of the genus Osteocephalus are moderate to large hylids. The largest species is taurinus, attaining a snout-vent length of 103.1 mm; the smallest is pearsoni, which attains a length of 54.7 mm. Considerable intraspecific geographic variation occurs in adult size, especially in taurinus. Females of all species attain a noticeably larger size than males, but no significant differences are apparent in proportions (Table 2).

TABLE 2.--Comparison of Size and Proportions in the Species of Osteocephalus. (Means are given in parentheses below observed ranges)

======================================================================================================== Species N Snout-vent Tibia Length/ Foot Length/ Head Length/ Head Width/ Tympanum/ Length S-V L S-V L S-V L S-V L Eye -------------------------------------------------------------------------------------------------------- O. buckleyi 30 37.9-48.1 0.478-0.580 0.375-0.444 0.319-0.357 0.329-0.368 0.608-0.820 (43.3) (0.520) (0.408) (0.343) (0.351) (0.711) 31 48.6-75.1 0.476-0.599 0.363-0.469 0.310-0.358 0.318-0.367 0.574-0.905 (61.7) (0.553) (0.428) (0.333) (0.348) (0.734)

O. leprieurii 21 41.2-48.4 0.514-0.571 0.383-0.430 0.308-0.357 0.326-0.368 0.652-0.884 (44.7) (0.538) (0.408) (0.335) (0.348) (0.777) 21 46.6-61.5 0.516-0.592 0.382-0.453 0.314-0.343 0.328-0.363 0.698-0.909 (57.1) (0.539) (0.404) (0.329) (0.349) (0.785)

O. pearsoni 2 45.3-46.2 0.481-0.504 0.404-0.437 0.322-0.335 0.327-0.342 0.660-0.673 (45.8) (0.493) (0.421) (0.329) (0.335) (0.666) 1 54.7 0.521 0.405 0.318 0.346 0.862

O. taurinus 59 40.3-84.6 0.512-0.576 0.387-0.445 0.296-0.345 0.301-0.355 0.638-0.896 (66.3) (0.541) (0.416) (0.318) (0.324) (0.752) 45 45.1-103.1 0.520-0.577 0.391-0.448 0.306-0.334 0.308-0.347 0.640-0.817 (75.8) (0.542) (0.420) (0.321) (0.327) (0.758)

O. verrucigerus 11 50.4-54.3 0.494-0.552 0.409-0.442 0.322-0.346 0.328-0.344 0.623-0.804 (53.0) (0.519) (0.427) (0.333) (0.337) (0.730) 3 63.1-65.8 0.532-0.561 0.435-0.463 0.345-0.347 0.348-0.379 0.692-0.808 (64.5) (0.545) (0.448) (0.346) (0.358) (0.731) --------------------------------------------------------------------------------------------------------

Coloration.--All Osteocephalus are predominantly brown frogs usually with some darker dorsal markings (Figs. 1 and 2). Osteocephalus verrucigerus has a nearly uniform dark brown dorsum and no distinct transverse bars on the limbs, whereas all of the other species have distinct bars on the limbs. The dorsal markings on the body consist of irregular blotches in buckleyi, pearsoni, and taurinus but are narrow transverse marks in leprieurii. A narrow middorsal cream or yellow stripe is present in some individuals of buckleyi and taurinus but absent in all individuals of the other species. The flanks are uniform pale tan in leprieurii and uniform reddish brown in verrucigerus; in the other species the flanks are cream to brown with dark brown or black spots (also dark diagonal marks in some buckleyi). A creamy white anal stripe is present in some specimens of leprieurii but absent in all individuals of other species.

The postocular region, encompassing the tympanum, is dark brown in most specimens. In adults of pearsoni and taurinus the upper lips are dark brown. A pale cream or tan suborbital spot is present in pearsoni and in some taurinus; in some specimens of taurinus the suborbital spot is expanded posteriorly forming a labial stripe on the posterior part of the lip. The labial markings of verrucigerus are similar to the latter pattern, except that in females a distinct, light labial stripe extends the length of the lip. Osteocephalus leprieurii has a distinct, broad, pale labial stripe. The lips are barred cream and dark brown in buckleyi.

The venter is uniform creamy white or pale tan in leprieurii, uniform white in some buckleyi (most males), and uniform tan in some taurinus. The other species and some individuals of taurinus and buckleyi (most females) have dark ventral markings. These markings are most distinctive in verrucigerus, in which the venter is white with bold black mottling and spots (Fig. 3c). Those individuals of taurinus having ventral markings usually have indistinct, diffuse brown spots on the throat and chest (Fig. 3b). Osteocephalus pearsoni is characterized by a fine brown reticulation on the venter and on the anterior and posterior surfaces of the thighs in adults (Fig. 3a). Individuals of buckleyi that have ventral markings vary between the patterns illustrated for pearsoni and taurinus (Figs. 3b and c).

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.

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 tubercles of leprieurii are numerous and spinous but much smaller than those of verrucigerus; those of taurinus are spinous but less numerous than in leprieurii. Osteocephalus buckleyi has a mixture of large and small, non-spinous tubercles, and pearsoni has only a few, small, scattered, non-spinous tubercles. Fleshy tubercles occur on the eyelids and supratympanic fold in females of buckleyi; a few small tubercles are present on the back of females of pearsoni, whereas the dorsal skin in females of the other species is smooth. The skin on the flanks of both sexes of buckleyi is weakly areolate; in the other species the flanks are smooth. The skin on the top of the head in taurinus is rugose as a consequence of co-ossification. In all species the anal opening is directed posteriorly at the upper level of the thighs.

Hands and Feet.--The feet of Osteocephalus are fully webbed or nearly so. Webbing between fingers one and two is basal in all species. Webbing between fingers two, three, and four is most extensive in taurinus, in which the three fingers are about one-half webbed (Fig. 5). Osteocephalus buckleyi, pearsoni, and verrucigerus have reduced webbing between fingers two and three, and leprieurii has reduced webbing between fingers two, three, and four. All members of the genus have well-developed subconical subarticular tubercles on the fingers and toes; there is a tendency for the distal tubercle on the fourth finger to be weakly bifid. Palmar and plantar supernumerary tubercles are well developed in taurinus, moderately developed in buckleyi, leprieurii, and pearsoni, and barely evident in verrucigerus. All of the species have a noticeable fold on the wrist and enlarged prepollices, bearing horny nuptial excrescences in breeding males. The prepollex is least enlarged in buckleyi. Outer metatarsal tubercles are absent. The inner metatarsal tubercle is moderately well developed and ovoid in leprieurii and pearsoni; it is elliptical and flat in the other species. Tarsal folds are absent in all species except verrucigerus, in which the folds are barely evident.

Cranium.--As a genus, the cranial structure is remarkably uniform and quite generalized when viewed in the context of the family Hylidae. The skulls are broad and relatively flat, each being only slightly more broad than long and about one-third as high as long. In dorsal aspect the snouts are broadly rounded; the snout of buckleyi is somewhat less rounded and appears to be slightly longer than the snouts of other species. This subtle difference relates to the relative narrowness of the premaxillaries in buckleyi.

The genus is characterized by well-developed dermal roofing bones and an unusually large exposure of the sphenethmoid dorsally (Fig. 6). The conformation of the sphenethmoid exposed dorsally is determined by the marginal positions of the adjacent, overlapping elements--the nasals and frontoparietals. Medially the nasals overlap the lateral margins of the sphenethmoid. Anteromedially, the nasals converge in leprieurii and taurinus, are narrowly separated in buckleyi and pearsoni, or are more widely separated in verrucigerus. In all species the nasals terminate at the anterodorsal corner of the orbit. The frontoparietals of buckleyi, leprieurii, and taurinus have an anterolateral extension, which marginally overlaps the dorsolateral edge of the sphenethmoid and articulates with the posterodorsal corner of the nasal in buckleyi and taurinus; the bones are narrowly separated in leprieurii. The frontoparietals of pearsoni and verrucigerus have more extensive median ossification and less extensive anterolateral ossification. Thus, in those species the posteromedian portion of the sphenethmoid is obscured, and the lateral margins are partly exposed. The frontoparietal fontanelle is completely covered in all species, except buckleyi and leprieurii, in which an irregular, median separation of the frontoparietals exposes a small portion of the fontanelle. The posterolateral margins of the frontoparietals lie medial to the epiotic eminences.

Dermal ornamentation, involving the nasals, frontoparietals, and sphenethmoid, occurs in taurinus and, to a limited extent, in pearsoni. 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).

The squamosals of all species are moderately large structures having otic plates that overlie the lateral portion of the cristae paroticae. The posterior rami are short; the zygomatic rami of all species, except taurinus, extend slightly more than one-half of the distance to the maxillary. In taurinus the zygomatic ramus extends nearly to, or articulates with, the maxillary.

The maxillary arches are complete and relatively robust. The alary processes of the premaxillaries are vertically oriented in leprieurii, pearsoni, and taurinus and very slightly inclined posteriorly in buckleyi and verrucigerus. The maxillaries are uniformly characterized by the absence of postorbital processes and by the presence of preorbital processes that articulate with the maxillary processes of the nasals. The partes facialae of the maxillaries are moderately developed in all species, except taurinus, in which the pars fascialis tends to articulate with the lateral margin of the nasal in well-ossified individuals. The partes palatinae are poorly developed in all species, except buckleyi, in which the pars palatina of the premaxillary is moderately robust.

The pterygoids are uniformly tri-radiate structures. The anterior rami terminate at about the mid-level of the orbit, and the medial rami articulate firmly with the anterolateral corner of the otic capsule. The palatines are well-developed elements bearing ventral ridges; the ridges are somewhat irregular in buckleyi, taurinus, and verrucigerus but smooth in leprieurii and pearsoni. The parasphenoids are large elements characterized by acuminate cultriform processes and posterolaterally inclined alary processes. The basal areas of the cultriform processes bear small odontoid protuberances in buckleyi, taurinus, and verrucigerus, whereas they are smooth in leprieurii and pearsoni. The prevomers are remarkably uniform, moderately well-developed structures. In each species the anterior ramus lies adjacent to the premaxillary, and the lateral wings form the anterior, medial, and posteromedial margins of the internal nares. The dentigerous processes are characteristically large and angular and bear numerous teeth. The sphenethmoid and otoccipitals are well ossified; a dermal sphenethmoid is present only in taurinus.