Part 4

In life dorsal coloration varied from pale green to olive-green with darker green or black flecks or reticulations, or pinkish tan to brown with dark brown flecks or reticulations. Some preserved specimens have relatively few dark flecks, whereas in most specimens the dorsum is heavily marked. All specimens have some white markings above the anus and on the posterodorsal surfaces of the thighs, but in some individuals the white flecks are expanded and interconnected forming an irregular white line.

Juveniles have a notably different coloration in life. The dorsum is uniform pale green; the anterior and posterior surfaces of the thighs, fingers, first three toes, and webbing are deep yellow. The anal stripe is creamy white, and the flanks are pale gray with black flecks. The upper lip, supratympanic fold, and canthal stripe are a bronze color. The belly is pale yellow with a silvery cast on the throat. Juveniles having snout-vent lengths from 24.5 to 36.6 mm. are so colored in life, and uniform dark bluish gray dorsally in preservative.

Comparisons.--The absence of a quadratojugal and the presence of a greatly enlarged, non-projecting prepollex place Hyla siopela in the Hyla bistincta group (see Duellman, 1964, and Adler, 1965). The presence of a rostral keel separates Hyla siopela from other members of the Hyla bistincta group, which is composed of two species having long anal sheaths (bistincta and pentheter), two small species having axillary membranes and lacking nuptial excrescences in breeding males (charadricola and chryses), and three species (crassa, pachyderma, and robertsorum) having short heads, round snouts, short anal sheaths, and nuptial excrescences in breeding males. Hyla siopela differs from the last three species in the shape of the snout and from each in certain structural features; H. crassa has fully webbed feet; H. pachyderma has large nuptial spines, and H. robertsorum has more webbing and a shorter tarsal fold. Furthermore, the venter in H. robertsorum is brown with creamy white flecks.

In structure and coloration H. arborescandens resembles siopela, but the former is smaller, and males of arborescandens have vocal slits.

Remarks.--This description brings to eight the number of species now recognized in the Hyla bistincta group. Hyla siopela is most closely related to Hyla robertsorum from the high mountains of the Sierra Madre Oriental in northern Puebla and eastern Hidalgo. Possibly the four species now recognized in the crassa subgroup (crassa, pachyderma, robertsorum, and siopela) are only subspecies of a single species, but differences in the amount of webbing in crassa and the nature of the nuptial excrescenses in pachyderma indicate that they are distinct species.

The type locality of Hyla siopela is a small stream cascading down the western slope of Cofre de Perote; the lower reaches of the stream can be reached by a dirt road leading east from the village of Perote for about 2 kilometers to a small park. The frogs were found in the stream at elevations of 50 to 100 meters higher than the park. The stream flows through a ravine supporting open, dry pine forest. Although the stream was searched thoroughly in February, 1966, no frogs were found. In July, 1966, adults and juveniles were found in crevices and under overhanging rocks behind small cascades and waterfalls by day and sitting on rocks and branches in the spray of cascades at night.

The specific name siopela is derived from the Greek siopelos, meaning silent, and alludes to the absence of a voice in this species.

Hyla altipotens new species

Plate 19

Holotype.--Adult male, KU 101001, from 37 kilometers (by road) north of San Gabriel Mixtepec (kilometer post 183 on road from Oaxaca to Puerto Escondido), Oaxaca, Mexico, elevation 1860 meters; obtained on February 19, 1966, by William E. Duellman.

Paratypes.--KU 101002-6 collected at the same locality on February 19 and 20, 1966, by William E. Duellman, and KU 101008 from 33 kilometers (by road) north of San Gabriel Mixtepec, Oaxaca, Mexico, elevation 1675 meters; obtained on February 20, 1966, by Linda Trueb.

Diagnosis.--A member of the Hyla taeniopus group characterized by a yellow venter, yellow flecks on posterior surfaces of thighs, bronze-colored stripe from snout, along canthus and edge of upper eyelid to point above arm, pointed snout, smooth dorsum, and no sexual dimorphism in shape of snout.

Description of holotype.--Adult male having a snout-vent length of 68.8 mm.; tibia length 36.2 mm., 52.6 per cent of snout-vent length; foot length (measured from proximal edge of inner metatarsal tubercle) 31.1 mm., 45.2 per cent of snout-vent length; head length 20.2 mm., 29.4 per cent of snout-vent length; head width 20.0 mm., 29.1 per cent of snout-vent length. Snout in lateral profile acutely rounded, protruding beyond tip of lower jaw, in dorsal profile pointed; canthus angular; loreal region flat; lips thick, barely flared. Snout long; nostrils slightly protuberant, directed dorsolaterally, situated about two-thirds distance from anterior corner of eye to tip of snout; internarial distance 5.6 mm.; internarial area slightly depressed; top of head flat; interorbital distance 6.0 mm., 30.0 per cent of width of head; width of eyelid 4.7 mm., 23.5 per cent of width of head. Diameter of eye 6.2 mm.; heavy dermal fold extending from posterior corner of eye, over upper edge of tympanum to point above insertion of arm; tympanum distinct, its diameter 3.4 mm., 54.8 per cent of that of the eye, separated from eye by distance equal to diameter of tympanum.

Axillary membrane absent; arms moderately robust, lacking dermal fold on lateral edge of forearm, having transverse fold on wrist; fingers moderately short, broad; length of fingers from shortest to longest, 1-2-4-3; discs large, that on third finger one-fourth larger than tympanum; subarticular tubercles large, round, none bifid; supernumerary tubercles large, granule-like, present only on proximal segments; prepollex enlarged, not bearing nuptial excrescence. Fingers about one-half webbed; webbing connects first and second fingers at level of distal end of antepenultimate phalanx, extending from middle of penultimate phalanx of second finger to middle of antepenultimate phalanx of third, and between bases of penultimate phalanges of third and fourth fingers. Heels overlap by about one-half length of shank when hind limbs adpressed; tibiotarsal articulation extends to point between eye and nostril; thin transverse dermal fold on heel; tarsal fold strong, extending full length of tarsus; inner metatarsal tubercle small, flat, elongate, barely visible from above; outer metatarsal tubercle small, conical; toes moderately long, stout; length of toes from shortest to longest, 1-2-3-5-4; discs slightly smaller than those on fingers; subarticular tubercles large, round, subconical; supernumerary tubercles large, conical, in single row on proximal segment of each digit; toes about four-fifths webbed; webbing extending from base of disc on first to base of disc on second to base of penultimate phalanx of third toe, from base of disc on third to base of penultimate phalanx of fourth to base of disc of fifth toe.

Anal opening directed posteroventrally at mid-level of thighs; anal sheath long, tubular. Skin smooth on dorsum and on ventral surfaces of shanks, granular on throat, belly, and ventral surfaces of arms and thighs. Tongue ovoid, widest posteriorly, neither notched nor free behind. Prevomerine teeth 6-7, situated on robust transverse ridges between small, ovoid choanae. Vocal slits absent. Testes large, ovoid, granular; length of left testis 11.0 mm.

Color (in preservative): brown above with many darker brown spots and narrow middorsal stripe on back; six or seven dark brown transverse bars on each segment of hind limbs and four bars on each forearm; flanks white with dark brown spots; anterior surfaces of thighs creamy white with brown reticulations; posterior surfaces of thighs dark brown with creamy yellow flecks; stripe on snout, canthus, edge of upper eyelid, and supratympanic fold tan; ventral surfaces of feet brown; rest of venter creamy white; stripe above anus white.

Color (in life): green above with slightly darker green spots; dorsal surfaces of upper arms and thighs tan with green transverse bars; upper surfaces of forearms and shanks green with darker green transverse bars; feet, fourth and fifth toes, and third and fourth fingers tan with brown transverse bars; other fingers and toes tan with brown flecks. Ventral surfaces creamy yellow, brightest on throat and chest; flanks and anterior surfaces of thighs bright creamy yellow with dark brown reticulations and spots; posterior surfaces of thighs and ventral surfaces of feet dark brown with yellow flecks; ventral surfaces of hands and webbing on hands and feet yellowish tan. Labial stripe tan; stripes on outer edge of forearm, along outer edge of foot, and above anus cream-color; stripe on canthus, edge of upper eyelid, and on supratympanic fold bronze-color. Iris pale bronze with black reticulations and faint median, horizontal copper-colored streak; pupil horizontally elliptical with ventral notch; palpebral membrane clear above, pale bluish green with brown reticulations below.

Variation.--In life all individuals had creamy yellow venters and yellow flanks and anterior surfaces of thighs with brown or black spots and mottling. Most of the adults were colored like the holotype, but one was a much darker olive-green, and one was uniform brown above with a dark brown middorsal stripe. Most subadults (snout-vent lengths 31.6-50.1 mm.) were pale reddish tan above with darker reddish brown bars on the limbs and blotches on the back. The side of the head was dark brown and the stripe along the canthus, edge of upper eyelid, and supratympanic fold was yellowish tan. Some individuals had a dark brown middorsal stripe. The posterior surfaces of the thighs were dull yellowish tan; yellow flecks were present in the larger individuals.

TABLE 2.--Variation in Measurements and Proportions in Hyla altipotens. (Means Are Given in Parentheses Below the Observed Range.)

=========+===+=============+=============+=============+============= | | Snout- | Tibia | Foot | Tympanum/ SEX | N | vent | length/ | length/ | eye | | length | S-V L | S-V L | ---------+---+-------------+-------------+-------------+------------- Males | 5 | 68.8-75.1 | 52.6-55.8 | 28.1-30.0 | 41.4-55.2 | | (70.7) | (53.7) | (29.2) | (50.6) | | | | | Females | 2 | 69.4-75.3 | 55.8-56.2 | 28.8-31.1 | 53.3-63.0 | | (72.4) | (56.0) | (29.9) | (58.8) ---------+---+-------------+-------------+-------------+-------------

The number of transverse bars on each thigh and shank varies from five to eight. The white stripe above the anus and the stripe from the snout along the side of the head are invariably present. In some of the largest individuals the brown reticulations on the anterior surface of the thigh extend onto the ventral surface; in these specimens brown flecks are present on the ventral surfaces on the shanks.

The tympanum is proportionately larger in females than in males; the variation in size and proportions is given in Table 2. The total number of prevomerine teeth varies from 13 to 18 (mean, 15) in five adult males and from 10 to 12 (mean 11) in two females.

The testes in all adult males are granular, ovoid in shape, and greatly enlarged. The lengths of the left testis in each of the five males are 11.0 to 23.5 (mean 14.6) mm.

Comparisons.--On the basis of external appearance and certain cranial characters (large frontoparietal fontanelle, broad sphenethmoid, large nasals broadly separated medially having thin lateral processes articulating with the palatines, short squamosal not articulating with the maxillary, and quadratojugal present and articulating with the maxillary), Hyla altipotens can be associated with the Hyla taeniopus group (Duellman, 1965, Lynch and Smith, 1966). Hyla altipotens can be distinguished from all of the other members of the group by its narrow head, pointed snout in both sexes, and uniformly yellow throat and belly.

Small brown individuals of Hyla altipotens superficially resemble adult Hyla pinorum. The latter species has a covered tympanum, less webbing on the hands, and a short, blunt snout.

Remarks.--This stream-breeding frog is like Hyla taeniopus in having greatly enlarged testes, which possibly through the production of vast quantities of sperm are an adaptation for successful breeding in torrential streams (Duellman, 1965:164).

All individuals were found in trees and bushes near streams in cloud forest at night in February. The type locality is the same as that of Hyla pentheter and Hyla thorectes, discovered by Kraig Adler in June, 1964. Our field work there in February, 1966, resulted in finding Hyla altipotens, H. pellita, and Ptychohyla leonhardschultzei, but no individuals of the species found by Adler. A visit to the same locality in August, 1966, revealed no individuals of either H. altipotens or pellita; instead pentheter and thorectes were found along the stream.

Duellman (1965:166) listed a specimen (TCWC 16184) of Hyla chaneque from Los Fustes, 3 kilometers east of San Sebastian, Oaxaca. Reexamination of this specimen reveals that it is Hyla altipotens. The frog was obtained by Dilford Carter on April 29, 1960; it was under a rock at the edge of a stream in an oak-pine-cypress association at an elevation of 1800 meters.