Splendid Leaf Frog

Cruziohyla calcarifer is a rare, moderate to large species of the genus Cruziohyla that attains a snout-vent length in males of 56.4 - 80.5 mm, and 57.0 - 88.8 mm in females (Gray 2018). The head is wider than long (Cochran and Goin 1970). The snout is short, broadly triangular from the dorsal view and sloping in the profile (Cochran and Goin 1970, Gray 2018). The slightly projecting nostrils are positioned more laterally than dorsally and closer to the upper lip than the eye. The internarial distance is slightly shorter than the distance from the nostril to the eye. The canthus rostralis is subtle. The loreal region is nearly vertical and slightly concave. The moderate-sized eye has a vertical pupil. The interorbital distance is slightly larger than the width of the upper eyelid and equivalent to the internarial distance (Cochran and Goin 1970). The tympanum almost touches the eye and is about 40 – 60% of the eye diameter (Cochran and Goin 1970, Gray 2018). The body is elongated with the post axillary region being noticeably narrower than the widest region of the head. The dorsal skin is finely granular with a glandular fold behind the tympanum extending to the angle of the jaw. The throat and chest are smooth (Cochran and Goin 1970). Breeding males have a single subgular vocal sac that is only slightly distensible (Duellman 2001). The belly and the ventral surfaces of the femur are uniformly granular. There are no lateral skin flaps between the limbs and no traces of skin folds across the chest or vocal sacs. There is a distinct flap above the vent. No inguinal gland is present (Cochran and Goin 1970). When the forelimb is extended posteriorly along the body and the hindlimb is adpressed along the body, the elbow and the knee overlap. The ulnar has a well-developed ridge extending from the elbow, along the outer arm to the tip of the fourth finger (Cochran and Goin 1970). The moderately webbed fingers have a webbing formula of I 2 - 2 - II 1+ - 2 III 1 ½ - 2 - IV (Gray 2018). The fourth finger is considerably longer than the second. The third finger, which has a disc approximately the size of the tympanum, is also longer than the second. There is no pollex (Cochran and Goin 1970). Like other Cruziohyla, breeding males have a spinous nuptial pad at the base of the thumb (Duellman 2001).The femur is just slightly shorter than the tibia and both are shorter than the foot. When the hindlimb is adpressed along the body, the heel extends beyond the tip of the snout. When held at right angles to the body, the heels overlap. The tarsus has a well-developed ridge extending along the outer margin of the foot to the tip of the fifth toe (Cochran and Goin 1970). There is a calcar on the heel that often terminates in two dermal processes, one projecting inward and the other outward (Gray 2018). The distinct inner metatarsal tubercle is oval. The outer metatarsal tubercle is still distinct but very small and round (Cochran and Goin 1970). The moderately webbed toes have a webbing formula of I 1 - 1+ II 1 - 2 III 1+ - 3 IV 3 - 2 - V (Gray 2018). The first toe is not opposable. It is shorter than the second, and the third and fifth toes are approximately equal in length. The disc of the fourth toe is about the same size as the tympanum (Cochran and Goin 1970).Cruziohyla calcarifer is distinguished from both other species in the genus, C. sylviae and C. craspedopus, by a combination of the following characters: (1) prominent dark brown ventral thigh markings present either side of the vent in both sexes; (2) small tympanum, diameter 40 – 60% that of the eye; (3) fingers and toes moderately webbed, approximately two-thirds (4) in life, upper surfaces uniform green, often having small white or pale blue spots; (5) in life, yellow-colored spot on the posterior rim of the eye when open; (6) short black bars to lateral surfaces of the flanks; (7) color of undersides, hands, feet, concealed surfaces of thighs and flanks, orange; (8) short sloping snout; (9) calcar on heel, often terminating in two dermal processes with one projecting inward and one projecting outward (Gray 2018).More specifically, the dark ventral markings found on the thigh region of C. calcarifer are not found on any other Cruziohyla species. The species lacks the lichenose marking found on the dorsal surfaces of both other Cruziohyla. Cruziohyla calcarifer also has a noticeably small tympanum, ranging between 40 – 60% the diameter of the eye compared with a tympanum size of 70 – 100% the diameter of the eye in C. sylviae. Juvenile C. sylviae and C. craspedopus lack the bright yellow markings above the mouth seen in C. calcarifer. Further distinctions between C. calcarifer and C. sylviae include C. calcarifer having more moderate webbing than C. sylviae, extending only to the antepenultimate phalanx on the 4th toe (Cochran and Goin 1970).In life, C. calcarifer has a uniform green dorsal skin surface with a scattering of very fine white or pale blue spots to the dorsal surfaces, recognized by Myers and Duellman (1982) and reported on by Ibáñez et al. (1999). The palpebral membrane not reticulated (Cochran and Goin 1970). The iris is a pale gray medially, and yellow on the periphery (Myers and Duellman 1982). The species has bright yellow flanks and thighs, with short, black, vertical finger-like bars extending approximately halfway down the flanks (Cochran and Goin 1970). The arms, excluding the dorsal surfaces of the forearms are deep orange, as are the hands and feet with the exception of the fourth finger and fifth toe. Those surfaces that are not orange have dorsal coloring and patterning (Myers and Duellman 1982). The nuptial pads are brown (Duellman 2001). The throat is yellow and the other ventral surfaces are yellow to orange (Myers and Duellman 1982). This species has dark ventral markings, which are a highly unusual feature to be found on any hylid frog: Developing into distinctive triangular patterning on the thighs this prominent characteristic develops soon after metamorphosis and is distinct before juveniles attain their adult coloration.When preserved, the dorsum becomes dark, deep blue and is sharply separated from the lighter ventral surface. The finger-like vertical bars on the flanks retain their black coloration. At the hip, the dorsal coloration extends along the dorsal margin of the thighs to the knees. The dorsal surface of the shanks, the metatarsal region, and the dorsal surface of the fifth toe also share the same dorsal coloration. Similar to the flanks, the thighs have finger-like projections from the dorsal margin towards the inner margin of the shank. The dorsal surfaces of the feet also have similar markings. The ventral surfaces of the wrist and fourth finger have brown markings. There are brown spots to the sides and posterior of the vent, and on the ventral surface of the metatarsal region, the base of the fourth toe, and the entire ventral surface of the fifth toe (Cochran and Goin 1970). Newly metamorphosed juvenile C. calcarifer show bright yellow markings above the mouth and on their lower eyelid (Cochran and Goin 1970, Gray 2018).Variation is noted in the extent of the outward facing calcar found on the heel: in all specimens from Costa Rica and Panama this feature is large, extensive, and marked with dark pigmentation; in some specimens from Colombia and Ecuador the outward-facing calcar on the heel is highly reduced and more rounded (Gray 2018). Breeding males have the secondary sexual characters of nuptial pads and vocal sacs (Duellman 2001).The species authority is: Boulenger, G.A. (1902) “Descriptions of new batrachians and reptiles from north-western Ecuador.” Annals and Magazine of Natural History, Series 7, 9, 51–57. https://doi.org/10.1080/00222930208678538Phylogenetic analysis of DNA sequences shows that C. calcarifer is highly divergent from both other members of the genus: DNA sequences of the 16S rRNA gene confirm C. calcarifer having minimum 6.2% genetic divergence from both C. sylviae and C. craspedopus (Gray 2018). The specific epithet “calcarifer” refers to the triangular dermal flap on the heel which points outward when the frog is at rest (from the Latin “calcar”, meaning “spur”, and “fero”, meaning “to carry”) (Duellman 1970).Between the species description in 1902 and 1970 only nine specimens were collected. The species description was made from a single specimen (Gray 2018).Until 2018 this species was confused with C. sylviae, which is much more commonly found and occurs from Panama to Honduras (Gray 2018).The dark ventral markings found on this species are a highly unusual feature to be found on any hylid frog and the presence and distinctiveness of these suggest a special function for this feature, although this is yet to be determined (Gray 2018). Tadpole descriptions for C. calcarifer have all focused on larval specimens collected in northern Costa Rica and Honduras, where only C. sylviae adults have been recorded and which are outside of the known distribution for C. calcarifer, As such, it is highly likely the tadpole of this species has yet to be described.

Highly restricted populations of C. calcarifer occur in northwest Ecuador, western Colombia, Panama, southeastern Costa Rica: Specifically, highly restricted populations occur from Esmeraldas Province in northwest Ecuador (Boulenger 1902; Cisneros-Heredia 2005; Coloma et al. 2008), through western Colombia at several reported localities (Boulenger 1913; Cochran and Goin 1970, Ruiz-Carranza et al. 1996). In Colombia, the species has been recorded in Municipal Mecana in the Chocó and Valle de Cauca (Vargas and Bolaños 1999, Lynch and Suárez 2004, Castro-Herrera and Vargas-Salinas 2008). The species is also found from Panama (Myers and Duellman 1982, Crawford et al. 2010), to the most southerly part of Costa Rica, where it was found in the Fila Carbon area of Comadre, Limón Province (Faivovich et al. 2010).

Cruziohyla calcarifer is a highly nocturnal species, which lives and reproduces in primary forest. Males have been heard calling high up in trees, however their vocalizations are soft, having little carrying power (Myers and Duellman 1982). The advertisement calls consist of single low-pitched notes of 135 – 212 milliseconds duration repeated at regular intervals (Gray 2018). Currently there is very little known about the reproduction of this species, although it is likely to be similar to other species in the genus: eggs laid on vines, roots or vegetation, over water.

Although rare, with less than 50 specimens documented in over 100 years, the conservation status of C. calcarifer, which is currently “Least Concern” is under assessment by the IUCN. Cruziohyla calcarifer is particularly rare and populations are highly restricted in all countries in which it is known to occur: In Ecuador the species is recorded very infrequently and where it occurs is under considerable human pressure (Stuart et al. 2008; Coloma et al. 2008); In Colombia, the species is recorded only at very few localities, mainly in the Chocó and Valle de Cauca (Castro-Herrera and Vargas-Salinas 2008) and information on the level of potential threats faced by the species there is limited; in Panama, only thirteen specimens are known (Myers and Duellman 1982; Crawford et al. 2010), the last 2 being found over 15 years ago; in Costa Rica only five specimens are currently known, the last being found in 1977.

Cruziohyla calcarifer, the splendid leaf frog or splendid treefrog, is a species of tree frog of the subfamily Phyllomedusinae described in 1902 by George Albert Boulenger. It has a distribution from Esmeraldas Province in northwestern Ecuador, through western Colombia and Panama to the most southerly part of Costa Rica. It is a nocturnal, arboreal frog inhabiting primary humid lowland forest.