Osteocephalus festae ( Peracca, 1904 )

Jungfer, Karl-Heinz, 2010, The taxonomic status of some spiny-backed treefrogs, genus Osteocephalus (Amphibia: Anura: Hylidae), Zootaxa 2407, pp. 28-50 : 33-36

Osteocephalus festae ( Peracca, 1904) nov. comb.

( Figs. 4 , 8 c)

This large frog was described on the basis of one specimen. The holotype, MZUT An. 208, is a female of 73.6 mm SVL with minute, immature eggs in the ovaries, from Valle de Santiago (= lower Río Zamora according to Trueb and Duellman 1971), Provincia Morona-Santiago, Ecuador. Trueb and Duellman (1971) synonymized festae with O. buckleyi . Their concept of the latter species then encompassed four species as understood here ( O. buckleyi , cabrerai , carri , festae ). Females of O. festae are considerably larger than those of O. buckleyi , similar in size to O. cabrerai , but much less tuberculate than the latter. A full description of the type specimen and variation in some additional material is given here.

Redescription of the holotype: The snout is rounded in dorsal and lateral view. The head is slightly wider than long. The lateral edges of the frontoparietals are not raised. The canthus rostralis is curved inward, weakly angular. The loreal region is oblique, concave. The nostrils are not elevated, opening anterolaterally. The lips are flared. The dentigerous processes of the vomers are angular, separated from each other, bearing 10 teeth on the left and 11 on the right. The vomers are situated between the choanae, their anterior edges at midlevel of the choanae, their posterior edges reaching slightly beyond the posterior edges of the choanae. Together, the dentigerous processes are slightly wider than the narrowest interchoanal distance. The choanae are large, oblique, ovoid, but somewhat angular. The tongue is elliptical, about 1.3 times wider than long.

The postocular area is oblique. There is a strong, smooth supratympanic fold from the posterior edge of the orbit sloping slightly arched towards the flanks almost to the lower tympanum level. The tympanum is elliptical (height 87% of width), with a distinct tympanic annulus that is partly concealed dorsally by the supratympanic fold. The tympanum is medium-sized, its diameter about 80% of the width of Finger III and 53% of the eye diameter. The orbit, however, has received pressure and the eye is difficult to measure. A flat tubercle on top of the orbit is still discernible.

Dorsal surfaces of the head, loreal region and postorbital area are shagreened, and tuberculate posteroventral to the tympanum. The skin of the body dorsally and dorsolaterally is smooth, as well as the dorsal and lateral surfaces of the extremities. Anterior to the arm insertion, ventrolaterally and ventrally (including the posterior gular area) the skin is areolate. The anterior gular area is granulate. The arms are smooth to slightly shagreen dorsally, otherwise smooth and without tubercles. An axillary membrane covers the proximal fourth of the upper arm posteriorly. Ventrally, the proximal half of the thighs is granulate, the other surfaces of the hind legs are smooth except for about three low elliptical tubercles on the inner ventrolateral edge of the tarsus. There are numerous minute circumcloacal warts. An anal sheath is absent.

The finger discs are ovoid. The diameter of the disc of Finger III is about 115% of that of the tympanum. The thumb bears a large elliptical thenar tubercle. The distal subarticular tubercle on Finger IV is single, but with a wide upper edge. The outer edge of Finger IV is fringed. The relative length of the adpressed fingers is I <II <IV <III. The webbing formula is I basal II 2 – — 3+ III 2 ¾ — 2 ½ IV. The plantar tubercles are low and flat. There is a large elliptical inner metatarsal tubercle. The outer edge of Finger I is fringed. The subarticular tubercles are single and conical. The proximal segments of Toes II–IV bear 2–4 low supernumerary tubercles. The relative length of the adpressed toes is I <II <III ≤ V <IV. The webbing formula is I 1 + — 2+ II 1 — 2 ½ III 1 + — 2½ IV 2 ½ — 1 V.

Measurements of the holotype (in mm): SVL 73.6; HL 24.9; HW 26.0; TL 43.2; FL 53.5; ED 7.3; TD 4.0; FD 4.6; EN 7.2; IN 5.5; TE 4.6.

Coloration: The dorsum is tan with bold dark brown blotches, the largest of them reaching from the anterior corners of the orbits posteriorly narrowing towards the posterior end of the occiput, widening then to form a Y-shaped mark with its both ends almost reaching the sacrum. There is another smaller blotch on the sacrum and another one posterior to it. Dark spots or lines are also present on the head anterior to the eyes. The head is dark brown laterally. There is a white subocular mark in the shape of an inverted V. The iris coloration is no longer visible. The postocular area is dark brown, the tympanum light brown. There are three dark irregular marks on the dorsal surfaces of the thighs as well as on the tibiae and two of them on the tarsus. The posterior and anterior parts of the hind legs and dorsal surface of the foot are uniform brown, ventrally light brown. The long bones of the tibia are green. Dorsal surfaces of the legs and posterior parts of arms with some dark blotches, ventral and anterior parts as well as hands ventrally light brown. There are some dark markings on palm and fourth finger. The lateral sides of the body are finely reticulate forming a mosaic of creamy yellow and brown spots. The ventral surfaces of throat and abdomen are creamy yellow marbled with brown irregular spots.

Variation: I have seen five more specimens, from Napo and Sucumbíos Province, Ecuador, but no live ones. Two additional females (EPN 5578 and MHNG 2560.60) are similar in size. The largest specimen with 78.9 mm SVL is EPN 5578. In this specimen the head is slightly longer than wide (HL/HW 1.01). The dorsal skin is smooth in MHNG 2560.60 and shagreen in EPN 5578. There are a few low tubercles on the dorsal surfaces of body and extremities of EPN 5578 that are lacking in MHNG 2560.60. Both specimens bear some low tubercles in the loreal and posttympanic area. On the eyelid there are one (MHNG 2560.60) and three (EPN 5578) tubercles. Both specimens have more webbing on the hand than the holotype, especially on the inner edge of the third finger, where the web almost reaches the ultimate subarticular tubercle. The distal subarticular tubercle on Finger IV is broadly rimmed distally like the holotype in MHNG 2560.60, but slightly bifid in EPN 5578.

Both specimens are similar to the holotype in their dorsal coloration, with bold dark bands between the eyes and large blotches on the back. Some of these are outlined creamy yellow on the head in EPN 5578 and also on the back in MHNG 2560.60. The venter is uniform light tan or tan.

Three males (EPN 5577, EPN AA-5611, EPN 5607) are 44.1–48.1 mm in SVL. The head is as long as wide in all specimens. The tympana in males are proportionately larger than in females (TD/HL 0.23–25 in females, 0.16–0.19 in males). All dorsal surfaces, the dorsolateral area of the flanks and the head laterally are more tuberculate than in the females. Although at least one of them (EPN AA-5611) has well-developed nuptial excrescences, none bears tubercles with keratinized tips on the dorsum. There are numerous tubercles on the posteroventral edge of tarsus and metatarsus and up to five ones on the orbit. The axillary membrane is more extensive than in females and covers about ½ of the upper arm proximally. The dorsal coloration is variable, with tan blotches, irregular streaks or a reticulum of tan on grey (most likely green in life) ground. The ventral surfaces of the body are creamy white with numerous speckles of brown. The tibiofibular bones are white in both males and females.

Comparisons: Osteocephalus festae differs from O. buckleyi (in parentheses) in larger size of the females of up to 78.9 mm SVL (up to 54.1 mm), dorsal tubercles without keratinized tips in breeding males (with tips), a medium-sized tympanum in females with TD/HL 0.16–0.19 (tympanum larger: TD/HL 0.20–0.23), a smooth supratympanic fold (tuberculate) and an axillary membrane covering about 3/8 (females) to ½ (males) of the proximal part of the upper arm (one fourth).

The species differs from O. cabrerai (in parentheses) in lacking a row of tubercles on the lower jaw (present), a row of low tubercles on the outer edge of Finger IV (an irregular deep fringe), webbing on the inner side of Finger III reaching the penultimate subarticular tubercle (proximal part of the ultimate subarticular tubercle, and continued as fringe to the finger disc), medium tympanum size in females with TD/ HL = 0.16–0.19 and TD/FD = 0.87–1.08 (large size with TD/HL 0.20–0.22 and TD/FD = 1.11–1.31), a smooth supratympanic fold (tuberculate) and uniform brown posterior surfaces of thighs in preservative (light tan with dark tan spots or irregular tan markings).

Osteocephalus inframaculatus (in parentheses) is a much smaller species. Female O. festae reach 78.9 mm SVL (41.9 mm). In addition, O. festae has a smooth supratympanic fold (tuberculate) and posterior surfaces of thighs in preservative are uniform brown (tan with light short vermiculation).

Osteocephalus festae may be diagnosed as (1) a medium to large-sized species with considerable sexual dimorphism in SVL (78.9 mm in females, 48.1 mm in males) and minor differences in dorsal tuberculation; (2) skin on dorsum of females smooth with or without a few granules, granulate in males; (3) skin on flanks areolate; (4) weakly angular canthus rostralis curved inward; (5) frontoparietal ridges not visible from outside; (6) dentigerous processes of vomers angular; (7) strong supratympanic fold from the posterior edge of the orbit sloping in an arch towards a point posterior to the jaw joint; (8) web on inner edge of third finger reaching distal end of penultimate subarticular tubercle or beyond, almost reaching the ultimate subarticular tubercle; (9) distal subarticular tubercle on Finger IV broad-edged to slightly bifid; (10) dorsum variable in shades of tan or grey (green in life?), with dark brown blotches, streaks, or a reticulate pattern; (11) venter creamy white with or without brown marbling or numerous brown speckles; (12) a large white subocular mark; (13) flanks marbled irregularly with light, tan and dark brown; (14) position of vocal sacs paired, protruding posteroventral to angles of jaws; (15) juvenile coloration unknown; (16) tadpole habitat and labial tooth row formula unknown (most likely in streams); (17) color of tibiofibular bones green or white in preservative.

Distribution: Osteocephalus festae is known from the Andean foothills in the provinces of Sucumbíos, Napo and Morona-Santiago, Ecuador.

Figures

FIGURE 4. Osteocephalus festae (holotype): a. dorsal, b. lateral, c. ventral view. Not to scale.

FIGURE 8. Hand and foot of a. Osteocephalus cabrerai (female holotype), b. O. buckleyi (SMNS 13713, female from Jatun Sacha, Napo, Ecuador), c. O. festae (female holotype). Some fingers and toes are spread with needles (not entirely shown), that may cover parts of the discs or intercalary tubercles. Not to scale.