Charadrahyla esperancensis, González-Bernal, 2017

González-Bernal, Edna, 2017, Discovery of another new species of Charadrahyla (Anura, Hylidae) from the cloud forest of northern Oaxaca, México, Zootaxa 4329 (1) : -

Charadrahyla esperancensis sp. n.

Esperanza Treefrog, Rana de la Esperanza (Figs. 1,2,3)

Holotype. ( Figs. 1 A,B,C ; 2 A,B,C). MZFC 28699 . Adult male. Arroyo Los tres manantiales, La Esperanza, Oaxaca, Mexico. 1640 mts. 17.6236° N, 96.3652° W, 19 October 2016. Edna González-Bernal.

Paratype. MZFC 28693 . Adult male. Dead on road near La Esperanza, Oaxaca, Mexico. 17.6275° N, 96.3625° W. 23 October 2016. Cynthia G. Ramírez-González.

Diagnosis. This species of Charadrahyla has a moderate size (males 44.3–48.9 mm SVL). It is distinguished from all members of the genus by the presence of a distinct rostral keel in a protuding snout with a downward slope posterior to the nostril; in lateral view, vocal slites absent and rounded yellow spots on flanks and on posterior and anterior surfaces of the thighs. Charadrahyla esperancensis is sympatric with C. nephila , but differs by its smaller size (males 44.3–48.9 vs 70.9 mm SVL), small dark brown spots on dorsum (vs large dark brown blotches on dorsum), dark transverse bars on fingers absent (vs present). The new species resembles superficially with C. taeniopus ( Fig. 1G,H ), but this species is distributed on the Atlantic Slopes in the states of Hidalgo, Puebla and Veracruz, whereas C. esperancensis is distributed on the Sierra Juarez at northern Oaxaca and it may be distinguished from C. taeniopus by having a evident rostral keel and vocal slites absent ( Fig. 2 C,D,E ).

Description of holotype. Body moderately slender, SVL 48.9 mm, tibia length 25.2 mm, foot length 22.06 mm, head length 16.63 mm, head width 16.79 mm, diameter of tympanum 2.61 mm, diameter of eye 4.36 mm, interorbital distance 5.85 mm, eye–tympanum distance 2.91 mm. Head as wide as long; snout pointed in dorsal profile, rostral keel evident ( Figs. 1C , 2C ); lateral profile protruding with snout slopes downward posterior to the nostril; canthus rostralis distinct and angular; loreal region concave; nostrils ovoid, slightly protuberant, directed posterolaterally; internarial region slightly concave. Top of head flat; interorbital region 34.8% of head width; diameter of eye 26.0 % of head width. Supratympanic fold distinct, thick, extending posteroventrally from posterior margin of orbit until insertion of forearm; tympanum distinct, round; tympanic annulus mostly distinct, obscured by supratympanic fold dorsally; width of tympanum 59.8% diameter of eye; width of tympanum 89.6% eye–tympanum distance. Axillary membrane absent; thoracic fold absent; dermal fold on wrist present. Fingers long and slender, with slightly lateral fringes, bearing large, rounded terminal discs; relative finger lengths: I <II <IV <III; discs on Fingers II, III, IV approximately equal in size, as wide as tympanum; disc on Finger I smaller, width 52.4% width of tympanum. Subarticular tubercles large, diameter about two-third width of terminal disc on same finger, rounded, none bifid; supernumerary tubercles smaller than subarticular tubercles, rounded, distinct.

Hand webbing formula: I 2–2 1/2 II 2–2 1/ 2 III 2 1/2– 2I V ( Fig. 3 ). Heels of adpressed hind limbs overlap, tibiotarsal articulation extending just past snout; tarsal fold absent; tibia length 51.5% SVL; foot length 45.1% SVL. Inner metatarsal tubercle distinct, large, ovoid, between 1.8 times larger than subarticular tubercles; outer metatarsal tubercle absent; subarticular tubercles distinct, large, elevated, rounded, diameter about one-half width of terminal disc on same toe; supernumerary tubercles small, rounded, arranged in rows along axis of proximal portions of phalanges. Toes long and slender, bearing rounded, terminal discs slightly smaller than discs on fingers. Foot webbing formula: I 1–1 1/2 II 1–2 III 1–2 IV 2–1 V ( Fig. 3 ). Cloacal opening directed posteroventrally at mid level of thighs. Skin on dorsal surfaces smooth; skin on ventral surfaces distinctly granular; skin on flanks between forelimbs and hind limbs distinctly thick and smooth.

Tongue large, cordiform (notched posteriorly), barely free posteriorly. Vomerine odontoids five on right side and six on left, situated on transverse, dentigerous processes at midlevel between choanae, choanae subtriangular, widely separated.

Color. In life ( Fig. 1A–C ), dorsum of body, head and lateral surfaces of head are pale brown. A dark brown mask in the lateral surfaces of head that begins in nostrils and continue until posterior part of tympanum. Dorsum with small distinct irregular dark brown spots. Dorsal surfaces of limbs pale brown with distinct dark brown transverse bars, three on forearm, four on thigh, and six on tibia; anterior and posterior surfaces of limbs with rounded and irregular small yellow spots; discs darker that fingers; flanks dark brown with distinctive irregular large yellow spots, some rounded. Venter of throat pale cream slightly mottled with irregular dark brown spots. Chest pale cream immaculate. Belly immaculate, granular. Undersurface of thighs pale cream and granular, palpebral membrane clear.

In preservative ( Fig. 2 A,B,C ), dorsum of body, head and lateral surfaces of head are dull gray, with small distinct irregular dark spots. Dorsal surfaces of limbs dull gray with distinct dark transverse bars, three on forearm, four on thigh, and six on tibia; anterior and posterior surfaces of limbs with rounded and irregular small pale cream spots. Flanks dark brown with distinctive pale cream large irregular spots, some rounded; venter of throat pale brown slightly mottled with irregular cream spots. Chest pale cream with irregular dark spots few scattered on anterior part. Belly pale brown, granular. Undersurface of thighs pale brown and granular, palpebral membrane dark gray.

Variation. The body measurements and coloration of the paratype (MZFC 28693) are as follow: SVL 5.49 mm, head length 18.91 mm, head width 17.24 mm, diameter of tympanum 3.11 mm, interorbital distance 7.43 mm. Snout slightly pointed in dorsal profile; lateral profile rounded. Fingers of hands and foots, broad. Terminal discs wide. Hand webbing formula: I 2–2 1/ 2 II 1 1/2–2 1/2 III 2-2 IV, foot webbing formula: I 1-1 II 1-1 1/2 III 1-2 IV 2-1 V. In preservative, dorsum of body, head and lateral surfaces of head are brownish green mottled with irregular dark spots. Dorsal surfaces of limbs pale gray with few dark transverse bars on thighs. Flanks pale brown with distinctive pale cream rounded spots. Venter of throat and chest immaculate, belly granular and immaculate. Undersurface of thighs pale gray and granular, venter palpebral membrane light. The color patterns of two additional live males (not collected) ( Fig. 1D–F ) were as follows: dorsum of body olive green, head copper brown and lateral surfaces of head dark brown, one specimen with a slender dark brown mask in the lateral surfaces of head ( Fig. 1D ). Dorsum almost immaculate or slightly mottled with irregular or rounded dark spots. Dorsal surfaces of limbs with four dark brown transverse bars on forearm, five on thigh, and six or seven on tibia; flanks dark brown with few or many distinctive rounded yellow spots in the anterior part of axillary region. SVL 45.9 and 44.3 mm.

Etymology. The specific epithet is taken from the Spanish word “Esperanza” referring the name of the town where this species is found. This is a recognition to the community effort to preserve the biodiversity of the local cloud forest.

Distribution and ecology. Charadrahyla esperancensis is known from a single locality at La Esperanza village in the Sierra de Juárez in northern Oaxaca, Mexico, at 1640 m elevation. This species was discovered at the margins of a mountain stream whose course has been diverted by the Oaxaca –Tuxtepec highway ( MX Hwy 175) ( Fig 4A ). The vegetation type is montane cloud forest with treeferns and oaks. The site receives an average 2000 mm of rainfall annually. The mean temperature is 18°C. The stream has a pebble and rock substrate and is not more than 5 meters wide. Due to steep slopes, it has several falls. The first specimen was found at night (21.44 hrs CST) at the margins of the stream, under the cover of fallen logs. The temperature at the time of discovery was 18°C with a 76% relative humidity. The mass was 9 g. It seems that on rainy nights this species tends to move considerable distances as another two individuals were found crossing the paved road from the village towards the forest. This species is sympatric with other endemic species: Charadrahyla nephila, Craugastor polymniae , C. spatulatus , Duellmanohyla ignicolor, Incilius spiculatus, and a number of salamander species. Among these species, C. nephila is considered as vulnerable, C.polymniae as critically endangered and C. spatulatus , D. ignicolor , and I. spiculatus as endangered by IUCN. All of these species are considered threatened by habitat destruction.

Figures

FIGURE 1. Specimens in life of Charadrahyla esperancensis: A, B, C: male holotype (MZFC 28699), D, E, F (male specimens, not collected) (F, same specimen that E, showing the rounded yellow spots on posterior parts of thighs, and C. taeniopus: G (male from Tlatlauquitepec, Puebla), H (female from Hidalgo).

FIGURE 2. Dorsal (A) and ventral view (B) of the preserved holotype of Charadrahyla esperancensis (MZFC 28699); dorsal and lateral view of the head of C. esperancensis (C); male (D) and female (E) of C. taeniopus (MZFC 5150, 7714 respectively).

FIGURE 3. Ventral aspects of hand and foot of the holotype of Charadrahyla esperancensis (MZFC 28699). Bar = 10 mm.

FIGURE 4. Type locality of Charadrahyla esperancensis (A), and Community cartel indicating the protection of the northern region where the new species lives (B)