Part 2

The fingers are long and slender in H. crassa, pachyderma, and robertsorum and somewhat shorter with more webbing in H. bistincta and charadricola. Breeding males of Hyla pachyderma have moderately large nuptial spines; the other species have small spines, except H. charadricola in which spines apparently are absent. A well-defined thoracic fold is present in H. pachyderma, and a weak fold is present in H. robertsorum; the other species lack folds. In all species there is an anal sheath; this sheath is longest in H. bistincta, in which the anal opening is directed ventrally at the level of the lower edge of the thighs.

TABLE 1.--COMPARISON OF CERTAIN MEASUREMENTS AND PROPORTIONS IN THE SPECIES OF THE HYLA BISTINCTA GROUP. (DATA FROM ADULT MALES; MEANS ARE GIVEN IN PARENTHESES BELOW THE RANGES.)

A: Snout-vent length B: Tibia length / Snout-vent length C: Head width / Snout-vent length D: Tympanum / Eye

==================================================================== SPECIES | N | | | | ---------------+----+-----------+-----------+-----------+----------- H. bistincta | 38 | 43.0-53.8 | 0.47-0.52 | 0.32-0.37 | 0.35-0.48 | | (46.3) | (0.49) | (0.34) | (0.42) | | | | | H. | 10 | 35.3-44.4 | 0.50-0.54 | 0.31-0.33 | 0.30-0.37 charadricola | | (40.4) | (0.52) | (0.32) | (0.34) | | | | | H. | 26 | 39.9-47.9 | 0.48-0.51 | 0.30-0.36 | 0.36-0.47 robertsorum | | (43.1) | (0.49) | (0.32) | (0.41) | | | | | H. pachyderma| 1 | 39.9 | 0.53 | 0.32 | ... | | | | | H. crassa | 1 | 53.7 | 0.50 | 0.33 | 0.28 ---------------+----+-----------+-----------+-----------+-----------

Frogs in this group are rather drab in appearance. The dorsal color varies from dull green to various shades of brown. The most distinct aspect of the coloration is the different color patterns on the flanks and posterior surfaces of the thighs. The flanks in all species are marked with spots or reticulations.

Hyla bistincta differs from other members of the group in having vocal slits and a distensible vocal sac. Only this species has been reported to call (Shannon, 1951:473). Insofar as is known, the other species are mute. Examination of skeletal preparations of H. bistincta, charadricola, and robertsorum and X-rays of the other species shows no notable specific differences in the osteology. Since the tadpoles of only H. bistincta (Duellman, 1961:47) and H. robertsorum (Rabb and Mosimann, 1955) are known, larval characters are of limited use in intra-group systematics.

Key to the Species of the Hyla bistincta Group

1. Snout, in dorsal profile, short and bluntly rounded; canthus rounded, sometimes indistinct, vocal slits absent 2

Snout, in dorsal profile, longer, squared; canthus distinct, vocal slits present or absent 4

2. Feet webbed to base of discs; dorsum dull olive green; flanks having cream-colored spots H. crassa, p. 486

Feet not webbed to base of discs; dorsum brown 3

3. Tarsal fold strong; thoracic fold heavy; webbing on feet extending to middle of penultimate phalanx of fourth toe; distinct white stripe above anus; cluster of largo spines on thumb in breeding males, H. pachyderma, p. 485

Tarsal fold weak and short; thoracic fold absent or barely indicated; webbing of feet extending to base of penultimate phalanx of fourth toe; no distinct white stripe above anus; nuptial tuberosities in breeding males consisting of small spines H. robertsorum, p. 481

4. Tarsal fold strong; anal flap elongate; anus opening at lower edge of femur; dorsum tan or brown; flanks mottled with cream and brown; venter immaculate creamy white; no anal stripe; vocal slits present, H. bistincta, p. 475

Tarsal fold faint and short; anal flap not elongate; anus opening at middle of femur; dorsum olive-green with black reticulations; flanks greenish gray with brown or black spots; a row of white flecks above and below anus, vocal slits absent H. charadricola, p. 478

ACCOUNTS OF THE SPECIES

In the following accounts complete synonymies are given for each species. In each account one specimen is described in detail; after this description the variation is discussed. In the list of specimens examined, localities are arranged alphabetically within the states, which also are given in alphabetical order. Localities given in italics are not shown on the accompanying maps (Figs. 2 and 4) due to crowding of symbols.

#Hyla bistincta# Cope

Hyla bistincta Cope, Proc. Amer. Philos. Soc, 17:87, August, 1877 [Holotype.--USNM 32261 from "most probably Veracruz," México; Francis Sumichrast collector]. Brocchi, Étude des batraciens de l'Amérique Centrale, p. 43, 1881. Boulenger, Catalogue Batrachia Salientia, 2nd Ed., p. 401, February 1, 1882. Sumichrast, La Naturaleza, 6:81, 1882. Cope, Bull. U. S. Natl. Mus., 32:14, 1887; Bull. U. S. Natl. Mus., 34:351, 1889. Günther, Biologia Centrali-Americana, Reptilia and Batrachia, pp. 265-6, June, 1901. Díaz de León, Indice de los batracios que se encuentran en la República Mexicana, p. 17, June, 1904. Nieden, Das Tierreich, Amphibia, Anura I, p. 247, June, 1923. Kellogg, Bull. U. S. Natl. Mus., 160:163-164, March 31, 1932. Taylor, Proc. Biol. Soc. Washington, 50:50-53, April 21, 1937; Univ. Kansas Sci. Bull., 26:389, November 27, 1940. Taylor and Smith, Proc. U. S. Natl. Mus., 194:87, June 7, 1948. Taylor, Univ. Kansas Publ. Mus. Nat. Hist., 1:261, August 16, 1948; Copeia, no. 4:272-273, December 15, 1949. Smith and Taylor, Univ. Kansas Sci. Bull., 33:346, March 20, 1950 [Type locality restricted to Acultzingo, Veracruz, México]. Rabb and Mosimann, Occas. Papers Mus. Zool. Univ. Michigan, 563:6-9, March 29, 1955. Duellman, Univ. Kansas Publ. Mus. Nat. Hist., 15:47-49, December 20, 1961.

Hyla bistincta labeculata Shannon, Proc. U. S. Natl. Mus., 101:470-473, figs. 92a, 93d, May 17, 1951 [Holotype.--USNM 123689 from San Lucas Camotlán, Oaxaca, México; Walter S. Miller collector]. Smith and Williams, Herpetologica, 19:23, April 11, 1963.

Hyla bistincta bistincta, Shannon, Proc. U. S. Natl. Mus., 101:472, May 17, 1951. Shannon and Werler, Herpetologica, 11:85, July 15, 1955. Smith and Williams, Herpetologica, 19:23, April 11, 1963.

Diagnosis.--Maximum snout-vent length in males 54 mm.; snout in dorsal profile truncate; tarsal fold strong; inner metatarsal tubercle large, high, and elongate; outer metatarsal tubercle absent; webbing on foot extending to middle of antepenultimate phalanx of fourth toe; nuptial spines on thumb small; thoracic fold absent; anal opening at level of lower edge of femur; dorsum brown or tan; belly cream-color; flanks creamy yellow with brown reticulations or spots; anal stripe absent; vocal slits present.

Description.--The following description is based on KU 68078 from Uruapan, Michoacán, México. Adult male having a snout-vent length of 43.2 mm.; tibia length, 22.1 mm., 51.1 per cent of snout-vent length; foot length (measured from proximal edge of inner metatarsal tubercle to tip of longest toe), 20.8 mm.; greatest width of head, 15.4 mm., 35.6 per cent of snout-vent length; head length, 13.9 mm., 32.1 per cent of snout-vent length; diameter of eye, 5.1 mm.; diameter of tympanum, 2.4 mm., 47.1 per cent of diameter of eye. Snout in lateral profile bluntly rounded, in dorsal profile truncate; canthus pronounced, rounded, not angular; loreal region slightly concave; lips thick, round, not flaring; nostrils slightly protuberant; internarial distance, 3.4 mm.; interorbital distance, 4.5 mm., somewhat broader than width of eyelid, 3.5 mm. A heavy dermal fold from posterior corner of eye above tympanum and curved downward to insertion of forearm; tympanum round, its diameter slightly more than its distance from eye. Forearm not robust; row of small pustules on ventral surface of forearm; fold on wrist; prepollex moderately enlarged, covered with small, horny, nuptial spines continuous on edge of digit; row of spines on inner surface of second finger; subarticular tubercles large, round, none bifid; supernumerary tubercles rather large, round; palmar tubercles rather small, flat, elliptical; fingers long, moderately slender; length of fingers from shortest to longest, 1-2-4-3; discs moderately large, that on third finger slightly larger than tympanum; rudimentary web between first and second and between second and third fingers; web between third and fourth fingers extending about one-fourth length of fourth finger. Heels overlap by about one-third length of shank when hind limbs adpressed; tibiotarsal articulation extends to anterior edge of eye; tarsal fold strong, extending to heel; inner metatarsal tubercle large, high, and elongate; outer metatarsal tubercle absent; subarticular tubercles moderately large, round; supernumerary tubercles small, in single rows on proximal segments of digits; toes moderately short; length of toes from shortest to longest, 1-2-3-5-4, third and fifth toes about equal in length; toes about two-thirds webbed; web extending to middle of antepenultimate phalanx of fourth toe, to discs of first, second, and fifth toes, and to base of penultimate phalanx of third toe; discs rather small, about two-thirds size of those on fingers. Anal opening at level of lower edge of thighs; anal sheath elongate, deeply creased medially; transverse dermal fold above anus. Skin of dorsal surfaces of head, body, and limbs faintly areolate; skin of chin, belly, and ventral surfaces of thighs granular, that of ventral surfaces of limbs, except thighs, areolate; thoracic fold absent. Tongue nearly round, slightly longer than wide, shallowly notched behind and barely free posteriorly. Vomerine teeth 4-4, situated on rounded vomerine ridges between rather small ovoid inner nares; vocal slits present, situated along posterior edge of each ramus.

Color (in alcohol) pale brown on dorsal surfaces of head, body, and limbs; flanks and anterior surfaces of thighs creamy white with dark brown reticulations; posterior surfaces of thighs tan with creamy white spots; belly cream-color; anal stripe absent.

Color (in life) pale tan on dorsal surfaces; flanks and anterior surfaces of thighs pale creamy yellow with purplish brown reticulations; posterior surfaces of thighs tan with yellow spots; ventral surfaces yellow; iris pale copper-color.

Variation.--There is little variation in structure. The total number of vomerine teeth varies from 6 to 14. In some individuals the supratympanic fold covers the upper part of the tympanum, but at least the lower part of the tympanum is always visible. The extent of the webbing between the toes varies from three-fourths to two-thirds complete. Usually the web extends to some point on the antepenultimate phalanx of the fourth toe, but in some specimens the web extends to the base of the penultimate phalanx.

In the large series of specimens from Uruapan, Michoacán, the coloration of the flanks and anterior surfaces of the thighs varies from nearly uniform creamy yellow with only fine dark reticulations to bold reticulations enclosing yellow spots. Some specimens from Oaxaca and Veracruz have slightly different markings on the flanks; in these the dark pigment is in the form of irregular spots or dashes, instead of reticulations.

There is considerable variation in color in the living frogs. The dorsum varies from greenish tan and pale yellowish tan to reddish brown, and some individuals are dark chocolate brown.