A Review of the Frogs of the Hyla bistincta Group Part 2

Color (in alcohol) of dorsal surfaces of head, body, and limbs dull grayish brown with indistinct scattered darker flecks; flanks grayish brown with cream-colored reticulations; posterior surfaces of thighs tan; chin cream-color, mottled with brown; belly creamy yellow; a.n.a.l stripe cream-color.

_Variation._--In addition to the specimen described above three others are known. One is a juvenile having a snout-vent length of 29.5 mm., and two are females having snout-vent lengths of 46.9 and 41.6 mm.

Variation in structure and coloration between the four specimens is slight. In the females the tympani are partly visible and are about one-third the diameter of the eye; the chest is mottled with brown; the a.n.a.l stripe extends laterally in the form of a row of cream-colored dashes and spots onto the posterodorsal surfaces of the thighs.

_Remarks._--On the basis of the four specimens available for study, _Hyla pachyderma_ seems to be closely related to _Hyla cra.s.sa_ and _Hyla robertsorum_. In the _Hyla bistincta_ group, _Hyla pachyderma_ is unique in having enlarged nuptial spines.

Taylor and Smith (1945:588) stated that the frogs were found on bushes and weeds beside a small, bounding stream near Pan de Olla.

I have searched unsuccessfully for this species in the area around Pan de Olla and Tezuitlan.

_Distribution._--This species is known only from a stream at an elevation of about 1600 meters on the Atlantic slopes of the Sierra Madre Oriental in central Veracruz (Fig. 4).

Specimens examined.--VERACRUZ: Pan de Olla, south of Tezuitlan, Puebla, USNM 115026-9.

#Hyla cra.s.sa# (Brocchi)

_Cauphias cra.s.sus_ Brocchi, Bull. Soc. Philom. Paris, ser. 7, 1:130, 1877 [Holotype.--MNHN 6331 from "Mexico;" Adolphe Boucard collector].

_Cauphias cra.s.sum_ Brocchi, etudes des batraciens de l'Amerique Centrale, p. 64, pl. 12, fig. 4, 1882. Diaz de Leon, Indice de los batracios que se encuentran en la Republica Mexicana, p. 21, June, 1904. Kellogg, Bull. U. S.

Nat. Mus., 160:118-120, March 31, 1932. Taylor, Univ. Kansas Sci. Bull., 26:392, November 15, 1940. Rabb and Mosimann, Occas. Papers Mus. Zool. Univ. Michigan, 563:7, March 29, 1955.

_Hyla cra.s.sa_, Boulenger, Catalogue Batrachia Salientia, 2nd. Ed., p. 396, February 1, 1882. Gunther, Biologia Centrali-Americana, Reptilia and Batrachia, p. 281, September, 1901. Nieden, Das Tierreich, Amphibia, Anura 1, p. 248, June, 1923. Smith and Taylor, Bull. U. S. Natl. Mus., 194:86, June 17, 1948. Taylor, Amer. Mus. Novitates, 1437:20, December 7, 1949.

_Hypsiboas cra.s.sus_, Cope, Bull. U. S. Natl. Mus., 32:14, 1887.

_Hyla robustofemora_ Taylor, Univ. Kansas Sci. Bull., 26:389-393, figs. 3-4, November 27, 1940 [Holotype.--UIMNH 25050 (formerly EHT-HMS 16314) from Cerro San Felipe, 15 kilometers northeast of Oaxaca, Oaxaca, Mexico; Edward H.

Taylor collector]; Univ. Kansas Sci. Bull., 28:310, November 15, 1942. Smith and Taylor, Bull. U. S. Natl. Mus., 194:86, June 17, 1948. Taylor, Amer. Mus. Novitates, 1437:20, December 7, 1949. Smith and Taylor, Univ. Kansas Sci. Bull., 33:339, March 20, 1950. Rabb and Mosimann, Occas. Papers Mus.

Zool. Univ. Michigan, 563:7, March 29, 1955.

_Plectrohyla cra.s.sa_, Hartweg, Occas. Papers Mus. Zool. Univ.

Michigan, 437:1, June 30, 1941. Stuart, Occas. Papers Mus.

Zool. Univ. Michigan, 455:6, January 5, 1942.

_Diagnosis._--Maximum snout-vent length in males 54 mm.; snout in dorsal profile round; tarsal fold strong; inner metatarsal tubercle small and elliptical; outer metatarsal tubercle small, flat, and indistinct; foot fully webbed; nuptial spines on thumb small; thoracic fold absent; a.n.a.l opening at level of middle of femur; dorsum dull olive-green; belly creamy yellow; chin gray with yellow flecks; flanks dull olive-green with scattered cream-colored spots; and stripe faint, cream-color; vocal slits absent.

_Description._--The following description is based on UIMNH 25050 from Cerro San Felipe, Oaxaca. Adult male having a snout-vent length of 53.7 mm.; tibia length, 26.9 mm., 50.1 per cent of snout-vent length; foot length (measured from proximal edge of inner metatarsal tubercle to tip of longest toe), 25.4 mm.; greatest width of head, 17.6 mm., 32.8 per cent of snout-vent length; head length, 16.0 mm., 29.8 per cent of snout-vent length; diameter of eye, 5.4 mm.; diameter of tympanum, 1.5 mm., 27.8 per cent of diameter of eye. Snout short, in lateral profile bluntly rounded, in dorsal profile broadly round; canthus absent; loreal region nearly flat; lips thick and not flaring; nostrils barely protuberant; internarial distance, 3.8 mm.; interorbital distance, 4.7 mm., somewhat broader than width of eyelid, 3.8 mm. Heavy dermal fold from posterior corner of eye above tympanum and then to insertion of forearm; tympanum concealed above, its diameter about equal to its distance from eye. Forearm thick; distinct fold on wrist; prepollex enlarged bearing patch of small nuptial spines continuous on side of digit; similar patch on second finger; subarticular tubercles small and round, none bifid; few supernumerary tubercles on proximal segments of digits; large, flat palmar tubercle; fingers long and slender; length of fingers from shortest to longest, 1-2-4-3; discs moderately large; rudimentary web between second and third fingers and between third and fourth. Legs thick; heels overlap by about one-fourth length of shank when hindlimbs adpressed; tibiotarsal articulation extends to posterior corner of eye; tarsal fold thick, extending to heel; inner metatarsal tubercle small and elliptical; outer metatarsal tubercle small, flat, and indistinct; subarticular tubercles small and round; single row of supernumerary tubercles on proximal segments of each digit; toes moderately short and slender; length of toes from shortest to longest, 1-2-3-5-4; toes fully webbed; flap of skin on inner surface of first toe; discs about same size as those on fingers. a.n.a.l opening directed posteroventrally at middle of thighs; a.n.a.l sheath moderately elongate; small tubercles below a.n.a.l opening. Skin of dorsum rather smooth, somewhat granular on dorsal surfaces of limbs; skin of chin and belly moderately granular; that of posterior surfaces of thighs smooth; no thoracic fold. Tongue nearly round, shallowly notched posteriorly, and free for about one-fourth its length; vomerine teeth 5-5, situated on rounded ridges between small inner nares; no vocal slits.

Color (in alcohol) dull olive-green on dorsal surfaces of head, body, and limbs; flanks dull olive-green with scattered cream-colored spots; posterior surfaces of thighs grayish brown with faint creamy mottling; chin gray with cream-colored spots; belly creamy yellow, suffused with gray posteriorly; undersides of feet and webbing gray; a.n.a.l stripe faint, pale cream-color.

_Variation._--The only other known specimen (MNHN 6331) is a female having a snout-vent length of 53.7 mm. and resembling the specimen described above in most details of morphology. In MNHN 6331 the tympanum is completely concealed, and the 8-7 vomerine teeth are arranged in two irregular rows. The female has more cream-colored mottling on the flanks and posterior surfaces of the thighs and more distinct mottling on the throat than the male described above.

_Remarks._--The systematic status of _Cauphias cra.s.sus_ Brocchi has been in doubt since the time of the original description. Brocchi (1877:130) stated: "Les dernieres phalanges sont obtuses, tronques a leur extremite anterieure." Brocchi placed the species in his genus _Cauphias_ (type species, _C. guatemalensis_), which he considered to be related to _Hylodes_ ( = _Eleutherodactylus_ in the sense used by Brocchi); he thereby placed _Cauphias_ in his Hylodidae ( = Leptodactylidae, in part). This idea of relations.h.i.+ps was perpetuated by Barbour (1927:96), who reported on the second known specimen of _Cauphias guatemalensis_ and stated: "When I dissected the sternum I was at once struck by its similarity to n.o.ble's figures of transitional types between arciferal and firmisternal forms. The _Cauphias_ sternum recalls some of his figures for _Sminthillus_ and _Eleutherodactylus_. This genus is probably most closely related to the latter and has probably become highly modified to meet some peculiar environmental condition or on account of some specialized habits as yet unknown." Kellogg (1932:118) placed _Cauphias_ in the Leptodactylidae and stated that the terminal phalanges are T-shaped.

Hartweg (1941:1) considered _Plectrohyla_ to be the correct generic name for _Cauphias guatemalensis_; he thereby relegated _Cauphias_ to the synonomy of _Plectrohyla_. Hartweg (1941:9) further showed that the terminal phalanges of _Plectrohyla guatemalensis_ were not T-shaped and that intercalary cartilages were present. Thus, he correctly concluded that _Plectrohyla guatemalensis_ (and _P. cra.s.sa_ by implication) was a member of the family Hylidae. Stuart (1942:6) followed Hartweg's allocations and further suggested that _Plectrohyla cra.s.sa_ might be the same species as _Hyla robustofemora_ Taylor. In his description of _H. robustofemora_ Taylor (1940:392), who had not examined the type of _Cauphias cra.s.sus_, stated that were it not for the statements of Brocchi and Kellogg that _C. cra.s.sus_ has T-shaped terminal phalanges, "I might suspect I had before me a specimen of _Cauphias_ closely related to _cra.s.sum_."

I have compared the type of _Cauphias cra.s.sus_ with that of _Hyla robustofemora_. With the exception of the minor differences mentioned in the preceding section on variation, the specimens are alike, leaving little doubt that they represent the same species. The statements of Brocchi and Kellogg to the contrary, the type of _Cauphias cra.s.sus_ possesses intercalary cartilages between the penultimate and terminal phalanges; the latter are not T-shaped, but as in the type of _Hyla robustofemora_, resemble those typical of _Hyla_. On the basis of the morphological characters, as pointed out for _Hyla robustofemora_ by Taylor (1940:392), _Hyla cra.s.sa_ is a member of the _Hyla bistincta_ group.

_Distribution._--This species is definitely known only from a small stream at an elevation of 2300 meters in the mountains of central Oaxaca (Fig. 4).

Specimens examined.--OAXACA: Cerro San Felipe, UIMNH 25050. "Mexico,"

MNHN 6331.

RELATIONs.h.i.+PS

The evolutionary trend in the members of the _Hyla bistincta_ group is towards aquatic habits. _Hyla bistincta_, the least specialized species in the group, has relatively short fingers, webbing between the fingers, a truncate, high snout, and relatively large subarticular and supernumerary tubercles. _Hyla charadricola_ resembles _bistincta_ in having relatively short fingers, a slight amount of webbing, and a truncate snout. Apparently these two species are more closely related to one another than either is to the other species in the group. _Hyla robertsorum_, _pachyderma_, and _cra.s.sa_ are the most aquatic members of the group. These species are closely related, possibly conspecific.

All have round, sloping snouts, robust forearms, long, unwebbed fingers, and large webbed feet. Both _H. pachyderma_ and _H. cra.s.sa_ seem to be advanced beyond _H. robertsorum_. If small nuptial spines, moderately webbed feet, and absence of a well-defined thoracic fold are considered to be less advanced than large nuptial spines and a strong thoracic fold, as in _H. pachyderma_, or fully webbed feet, as in _H. cra.s.sa_, then _H. robertsorum_ must be considered to be less advanced than _H. pachyderma_ or _H. cra.s.sa_.

Members of the _Hyla bistincta_ group inhabit mountain streams. The frogs can be found along these streams throughout the year. Since in most stream-breeding hylids there is no migration to breeding sites, the breeding call does not function to attract females to the breeding site. Apparently voices are lacking in all members of the _Hyla bistincta_ group, except in _Hyla bistincta_. The presence of vocal slits and the ability to call further indicate that _Hyla bistincta_ is the primitive member of this group.

Members of the _Hyla bistincta_ group and the species of _Plectrohyla_ closely resemble each other in osteology and body form of the adults and in structure of the tadpoles. This resemblance suggests a close relations.h.i.+p between the two groups. _Plectrohyla_ apparently evolved from an ancestral stock resembling the extant _Hyla bistincta_.

Probably this stock gave rise independently to _Plectrohyla_ and to the _Hyla robertsorum-pachyderma-cra.s.sa_ complex. In the former the voice was retained, and a projecting prepollex spine developed, whereas in the latter the voice was lost, and the prepollex spine did not project. _Plectrohyla_ lives in mountain streams in the Chiapan-Guatemalan highlands; the _Hyla robertsorum-pachyderma-cra.s.sa_ complex inhabits similar environments in the Sierra Madre Oriental in Mexico. _Hyla charadricola_ also lives in the Sierra Madre Oriental, whereas _Hyla bistincta_ is widespread in the mountains of Mexico southeastward to the Isthmus of Tehuantepec.

LITERATURE CITED

BARBOUR, T.

1927. _Cauphias_ rediscovered. Copeia, no. 165:96-98, December 23.

BROCCHI, P.

1877. Note sur quelques batraciens hylaeformes recueillis au Mexique et au Guatemala. Bull. Soc. Philom. Paris, ser.

7, 1 (3):122-132.

DUELLMAN, W. E.

1961. The amphibians and reptiles of Michoacan, Mexico. Univ.

Kansas Publ. Mus. Nat. Hist., 15:1-148, pls. 1-6, December 20.

HARTWEG, N.

1941. Notes on the genus _Plectrohyla_, with descriptions of new species. Occas. Papers Mus. Zool. Univ. Michigan, 437:1-10, pl. 1, June 30.

KELLOGG, R.

1932. Mexican tailless amphibians in the United States National Museum. Bull. U. S. Natl. Mus., 160:iv + 224 pp., pl. 1, March 31.

RABB, G. B. and MOSIMANN, J. E.

1955. The tadpole of _Hyla robertsorum_, with comments on the affinities of the species. Occas. Papers Mus. Zool. Univ.

Michigan, 563:1-9, March 29.

SHANNON, F. A.