Part 4

_Etymology._--Latin, _nebula_, in reference to the clouded dorsal pattern.

_Distribution._--Low to moderate elevations along the Pacific versant of Chiapas and in the Grijalva valley of Chiapas and Guatemala (Fig. 17).

_Specimens examined._--(54) GUATEMALA, _Huehuetenango_: Jacaltenango, UMMZ 117036; 35 km. SE La Mesilla, TNHC 29652. MÉXICO, _Chiapas_: 11.2 km. N Arriaga, 300 m., UMMZ 125891; 11.8 km. N Arriaga, UMMZ 117279; 12.8 km. N Arriaga, UMMZ 117280; 17.5 km. S Arriaga, UIMNH 57108-109; 1.5 km. S Bochil, 1250 m., KU 58898-908; Cerro Hueco, 7 km. S Tuxtla Gutierrez, UMMZ 123007; 3.2 km. S Ixtapa, UMMZ 124000; Linda Vista, ca. 2 km. NW Pueblo Nuevo Solistahuacán, KU 58897; Hda. Monserrate, 40 km. NW Arriaga, UMMZ 102258; near San Ricardo, FMNH 100720; Tapachula, FMNH 75792, 103242, 100695-96, UIMNH 13292; 56 km. E Tapanatepec, Oaxaca, TNHC 26942, Tonolá, FMNH 100095 (holotype), 100686-92, UIMNH 13293-95; Tuxtla Gutierrez, FMNH 100693-94, UIMNH 13297; 19 km. N Tuxtla Gutierrez, TNHC 25229-30; 15.5 km. NE Tuxtla Gutierrez, UMMZ 119892 (3); 19 km. NE Tuxtla Gutierrez, UMMZ 119891 (3); 8 km. NNW Tuxtla Gutierrez, KU 37809; Unión de Juarez, FMNH 105294.

=Syrrhophus pipilans pipilans= Taylor

_?Syrrhopus verruculatus_: Gadow, 1905:194.

_Syrrhophus pipilans_ Taylor, 1940c:95-97, pl. 1 [Holotype.--FMNH 100072 (formerly EHT-HMS 6843), from 14.6 km. S Mazatlán, Guerrero, México; collected on July 22, 1936, by Edward H. Taylor]. Taylor and Smith, 1945:581-82. Smith and Taylor, 1948:49, 50-51.

_Syrrhophus pipilans pipilans_: Duellman, 1958:1-4, 8-9, 13-14, pl. 2, fig. 1. Gorham, 1966:166.

_Diagnosis._--Diameter of tympanum 40.6-54.0 per cent that of eye; dorsum dark brown with large light spots or blotches.

_Remarks._--Duellman's (1958) synopsis of this subspecies is adequate; the distribution has not been extended, but several records are now available which fill in gaps.

Gadow's (1905) record of _S. verruculatus_ from "Buena Vista, S. Guerrero" is most likely applicable to this species. Gadow simply included the name in a list of the species he had collected during his trip in México (1902-04); no further comment was made on this species although references to _Syrrhopus_ (sic) appear in several places in the paper and would appear to apply to the species he had.

_Etymology._--Latin, _pipilo_, chirping, peeping, in reference to the call of the male.

_Distribution._--Sea level to about 1800 meters along the Pacific versant of western México from central Guerrero to the Isthmus of Tehuantepec (Fig. 17).

_Specimens examined._--(62). MÉXICO, _Guerrero_: Acapulco, UMMZ 110125; 6.4 km. N Acapulco, FMNH 100389, 100525; Agua del Obispo, 980-1000 m., FMNH 75791, 100518-21, 100526, KU 86884-86, UIMNH 13315, UMMZ 119152, 125890 (4); 13.3 km. NW Coyuca, UIMNH 38367, 71982-83; 14.5 km. S Mazatlán, FMNH 100072 (holotype), 100408, 100511-17, UIMNH 13302-309; Tierra Colorado, 300 m., KU 67961, UIMNH 13313-14; near El Treinte, FMNH 126639; Xaltinanguis, FMNH 100522-24, 126640. _Oaxaca_: Cacahuatepec, UIMNH 52853; 8 km. NW Río Canoa, 53 km. ESE Cuajinicuilapa, UIMNH 52852; 6.4 km. N El Candelaria, UIMNH 9501; 11.2 km. S El Candelaria, UIMNH 9502; 17 km. NE Juchatengo, 1600 m., KU 86887; 31.5 km. N Pochutla, UMMZ 123999 (2); 32.9 km. N Pochutla, 850 m., UMMZ 123996; 37.1 km. N Pochutla, UMMZ 123998 (2); 41.4 km. N Pochutla, UMMZ 123997 (2); Cerro Quiengola, FMNH 105653; 3.8 km. N Santiago Chivela, UMMZ 115449; 14.5 km. W Tehuantepec, UMMZ 115448 (2).

=Syrrhophus interorbitalis= Langebartel and Shannon

_Syrrhophus interorbitalis_ Langebartel and Shannon, 1956: 161-65, figs. 1-2 [Holotype.--UIMNH 67061 (formerly FAS 9378), 36 mi. N Mazatlán, Sinaloa, México, collected on November 17, 1955, by E. C. Bay, J. C. Schaffner, and D. A. Langebartel]. Duellman, 1958:1-4, 10, 12, 14. Gorham, 1966:164-65.

_Syrrhophis interorbitalis_: Campbell and Simmons, 1962:194, fig. 1.

_Diagnosis._--Medium sized frogs, only known male 25.6 mm. snout-vent, females 20.0-26.7 mm. snout-vent length (small sample); vocal slits in males; finger tips expanded; first finger shorter than second; outer metatarsal tubercle one-third size of inner; skin of dorsum shagreened, that of venter smooth; diameter of tympanum 37.7-42.4 per cent that of eye in both sexes; pale yellow-brown ground color mottled with brown; limb bands broad, much wider than narrow light interspaces; interorbital bar very long, edged with dark brown to black (Fig. 18).

_Remarks._--Duellman's (1958) measurements and proportions of _S. interorbitalis_ were based exclusively on the type series, which is composed of only females; therefore his _interorbitalis_ data are not comparable with the data for the other species in his table. Campbell and Simmons (1962) collected the only known male. The type series was collected beneath rocks in a stream bed; the collectors heard calling frogs in the bushes but were unable to obtain specimens (Langebartel and Shannon, 1956). Campbell and Simmons (1962) reported that their specimen had a poorly developed interorbital bar in life; in preservative the bar compares favorably with the bar in the female (Fig. 18).

_Etymology._--Latin, in reference to the pale interocular band.

_Distribution._--Pacific lowlands of Sinaloa, México (Fig. 20).

_Specimens examined._--(10). MÉXICO, _Sinaloa_: 36 mi. N Mazatlán, UIMNH 38094-96, 67061 (holotype), 71970-74; 65 mi. N Mazatlán, LACM 13773.

=Syrrhophus modestus= Taylor

_Syrrhophus modestus_ Taylor, 1942:304-06, pl. 29 [Holotype.--FMNH 100048 (formerly EHT-HMS 3756), from Hacienda Paso del Río, Colima, México; collected on July 8, 1935, by Hobart M. Smith]. Smith and Taylor, 1948:49-50.

_Syrrhophus modestus modestus_: Duellman, 1958:2-5, 7, 14, pl. 1, fig. 1. Gorham, 1966:166.

_Diagnosis._--Small frogs, males 15.8-20.1 mm. snout-vent length, single female 18.5 mm.; vocal slits present in males; finger tips widely expanded; first finger shorter than second; inner metatarsal tubercle about three times size of outer; skin of dorsum shagreened, that of venter smooth; tympanum concealed; pale cream in preservative with dark brown spots; limbs banded; bands on forearm and thigh poorly developed or absent; interorbital bar absent.

_Remarks._--The tympanum is concealed in _S. modestus_, _S. nivocolimae_, _S. pallidus_, _S. teretistes_, and to a lesser degree in _S. interorbitalis_. However, if the specimen is permitted to dry slightly, the annulus tympanicus becomes visible through the skin and a tympanum/eye ratio can be computed.

One of the few cases of sympatry within the genus _Syrrhophus_ involves this species; _modestus_ and _nivocolimae_ are known to be sympatric at one locality in southwestern Jalisco, México.

Duellman (1958) used the trinomial for this population and named a new subspecies, _pallidus_, from Nayarit. I consider _pallidus_ to be specifically distinct from _modestus_ because there is no evidence of genetic exchange, and there is no overlap in the distinguishing morphological features. I do consider the two populations to be closely related but feel the interrelationships between _modestus_, _pallidus_, _nivocolimae_, and _teretistes_ are more complex than would be indicated by the use of trinomials. The sympatric occurrence of _modestus_ and _nivocolimae_ is significant; morphologically, they might otherwise be regarded as subspecies. Although allopatric, similar arguments could be advanced for the morphologically similar _pallidus_ and _teretistes_. The four are here afforded species rank since morphological similarity and allopatry are not sufficient grounds for the assumption of genetic exchange.

_Etymology._--Latin, meaning unassuming, modest, in reference to the small size of the species.

_Distribution._--Low elevations (up to 700 meters) in the lowlands and foothills of Colima and southwestern Jalisco, México (Fig. 20).

_Specimens examined._--(14). MÉXICO, _Colima_: Hda. Paso del Río, FMNH 100048 (holotype), 100167, 100299, UIMNH 13300, UMMZ 110877 (2), USNM 139729; 7.2 km. SW Tecolapa, UMMZ 115477 (4); _Jalisco_: 17.6 km. SW Autlan, 606 m., KU 102627; 3.2 km. N La Resolana, UMMZ 102100; Bahía Tenacatita, UMMZ 84264.

=Syrrhophus nivocolimae= Dixon and Webb

_Syrrhophus nivocolimae_ Dixon and Webb, 1966:1-4, Fig. 1 [Holotype.--LACM 3200, from Nevado de Colima (6 airline miles west of Atenquique), Jalisco, México, 7800 feet; collected on July 20, 1964, by Robert G. Webb].

_Diagnosis._--Small frogs, males 18.5-21.1 mm. snout-vent length, only known female 24.1 mm. snout-vent; vocal slits present in males; finger tips widely expanded; first finger shorter than second; inner metatarsal tubercle about three times size of outer; skin of dorsum warty, that of venter smooth; tympanum concealed, its diameter 30.0-39.3 per cent that of eye in males; mid-dorsal brown band from interorbital bar to anus; bands on limbs narrow, dark bands less than one-half width of light bands, upper arm not banded; narrow interorbital light bar.

_Remarks._--This species is closely related to _S. modestus_ and differs in color pattern and degree of wartiness of the skin. Dixon and Webb (1966) held that _nivocolimae_ had no close relatives, but the condition of the tympanum, size, nature of the outer palmar tubercle, relative sizes of the metatarsal tubercles, and shape and size of the digital pads all point to a close relationship between _S. modestus_, _S. nivocolimae_, and _S. pallidus_.

Dixon and Webb (1966) reported that _S. nivocolimae_ has a large tympanum (50.0-59.0 per cent diameter of eye). However, my examination of the type series and several other specimens from Jalisco reveals that the largest tympanum/eye ratio is 39.3 per cent. Therefore, the tympanum/eye ratio in _S. nivocolimae_ is in agreement with those for _S. modestus_, _S. pallidus_, and _S. teretistes_ (Table 6).

_Etymology._--_niv_, Latin, and Colima (Nevado de), meaning high on the volcano, in reference to the higher distribution of this species (around 2000 meters) than other members of the group.

_Distribution._--Known from southwestern Jalisco, México, at moderate to high elevations (600-2400 meters).

_Specimens examined._--(48) MÉXICO, _Jalisco_: 17.6 km. SW Autlán, 606 m., KU 102626, 102631; 6.4 km. W Atenquique, 2060 m., KU 102628-30, 102632; 8 km. W Atenquique, 1970 m., LACM 3210-12; 9.6 km. W Atenquique, 2360 m., LACM 3200 (holotype), 3201-09; 14.5 km. W Atenquique, 2000 m., LACM 25424-36, 25439-41, 25446; 15 km. W Atenquique, LACM 37044-46, 37244-47; 16 km. W Atenquique, 2105 m., LACM 25443-45; 17 km. W Atenquique, 2180 m., LACM 25442.

=Syrrhophus pallidus= Duellman, New combination

_Syrrhophus modestus_: Davis and Dixon, 1957:146.

_Syrrhophus modestus pallidus_ Duellman, 1958:2-3, 5-7, 14, pl. 3 [Holotype.--UMMZ 115452, from San Blas, Nayarit, México, sea level; collected on August 13, 1956, by William E. and Ann S. Duellman]. Zweifel, 1960:86-88, 91, 93-94, 118, 120-22. Gorham, 1966:166.

_Syrrhophis modestus pallidus_: Campbell and Simmons, 1962:194.

_Diagnosis._--Small frogs, males 17.9-19.3 mm. snout-vent length; vocal slits in males; finger tips widely expanded; first finger shorter than second; inner metatarsal tubercle about three times size of outer; skin of dorsum shagreened, that of venter smooth; tympanum concealed, its diameter 27.0-35.6 per cent of eye in males; ground color cream vermiculated with brown, upper arm and thigh lacking, or with few, indistinct, bands; interorbital bar absent.

_Remarks._--Considerable debate has been waged relative to the value of subspecies and to the reasons for recognizing distinct disjunct populations as species versus subspecies. Lacking evidence of genetic exchange, I prefer to retain disjunct populations that are distinctive as species.

All known specimens of _pallidus_ can be separated from those of _modestus_ by color pattern. The two nominal species exhibit overlap in proportions but the same can be said about nearly every species of _Syrrhophus_; therefore, overlap in proportions can be disregarded in assessing specific versus subspecific rank. Until contrary evidence is forthcoming, I consider the disjunct populations heretofore held to be subspecies of _modestus_ to be specifically distinct. The specimens of the disjunct population of _pallidus_ on the Tres Marias do not differ from the mainland population in Nayarit. This evidence, though perhaps secondary, supports my contention that two species should be recognized.

_Etymology._--Latin, in reference to the pale ground color in comparison with that of _S. modestus_.

_Distribution._--Low elevations in coastal Nayarit and on Islas Tres Marias (Fig. 20).

_Specimens examined._--(12) MÉXICO, _Nayarit_: 18.8 mi. NW Ahuacatlán, UIMNH 7808; San Blas, UMMZ 115452 (holotype), 115453-57; 17 km. NE San Blas, 150 m., MSU 5085; 12.8 km. E San Blas, UIMNH 71979; 31 km. E San Blas, UIMNH 71978; 13.5 km. N Tepic, UIMNH 71980-81.

=Syrrhophus teretistes= Duellman

_Syrrhophus teretistes_ Duellman, 1958:2-3, 10-14, pl. 2, fig. 2 [Holotype.--UMMZ 115451, from 4.8 km. NW Tepic, Nayarit, México, 840 m.; collected on August 12, 1956, by William E. Duellman]. Gorham, 1966:167.

_Diagnosis._--Medium-sized frogs, males 19.2-23.2 mm. snout-vent length, single known female 24.8 mm. snout-vent; vocal slits in males; finger tips widely expanded; first finger shorter than second; inner metatarsal tubercle about three times size of outer; skin of dorsum shagreened, that of venter smooth; tympanum partially concealed, its diameter 28.6-43.8 per cent of eye in males; ground color brown vermiculated with dark brown to nearly black; upper arm and thigh banded; interorbital light bar absent.

_Remarks._--_S. teretistes_ appears to be most closely related to _S. pallidus_; I consider it to be an upland derivative of _pallidus_. Morphologically, the differences between the two are few, but lacking evidence of genetic exchange they are retained as species.

_Etymology._--Greek, in reference to the whistle-like nature of the call.

_Distribution._--Moderate elevations (840-1200 meters) in the Sierra Occidental of Nayarit, Sinaloa, and Durango, México (Fig. 20).

_Specimens examined._--(13) MÉXICO, _Nayarit_: 4.8 km. NW Tepic, 840 m., UMMZ 115451 (holotype). _Sinaloa_: Santa Lucía, 1090 m., KU 75263-72; 1 km. NE Santa Lucía, 1156 m., KU 78257; 2.2 km. NE Santa Lucía, 1156 m., KU 78258.

DISCUSSION

There are relatively few clear-cut morphological differences among the fourteen species now assigned to _Syrrhophus_. The majority of the species are allopatric and differ primarily in color patterns. Sympatric occurrence serves as an indicator of specific distinctness and is one of the more practical tests of species validity when cross-breeding experiments are not possible. Two cases of sympatric occurrence are known for the species of _Syrrhophus_ in western México: _modestus_ and _nivocolimae_ are sympatric in southern Jalisco and _pipilans nebulosus_ and _rubrimaculatus_ are sympatric in southeastern Chiapas. In eastern México, _longipes_ and _verrucipes_ are sympatric in southern Hidalgo, and _longipes_ is sympatric with _cystignathoides_, _dennisi_, and _guttilatus_ in southern Tamaulipas. _Syrrhophus cystignathoides_ and _leprus_ are apparently sympatric in central Veracruz.

Subspecific assignments have been made only when there is evidence of intergradation. The sympatric occurrence of morphologically similar species in this genus has led me to adopt a conservative approach to the degree of difference philosophy. I have therefore recognized all morphologically distinct allopatric populations as species.

_Syrrhophus_ is closely allied to another Mexican leptodactylid genus, _Tomodactylus_, which was revised by Dixon (1957), who along with numerous other authors noted the close relationship between the two genera. There is an almost complete lack of sympatry between the two genera; in very few places in México do they coexist (Fig. 21). _Tomodactylus_ has its greatest diversity in the Cordillera Volcánica and Sierra Madre del Sur, whereas _Syrrhophus_ reaches its greatest diversity in the Sierra Madre Oriental and eastern foothills. The species of both genera are about the same size and presumably have similar requirements insofar as food, breeding sites, and habitat selection.

Four cases of intergeneric sympatry are known for the two genera: 1) the Chilpancingo region of Guerrero, 2) the lowlands of Colima and the mountains just inland in Jalisco, 3) the lowlands of central Nayarit, and 4) the Sierra Madre Occidental on the Durango-Sinaloan border. The apparent sympatry in the Chilpancingo region involves four species: _S. pipilans_, _T. albolabris_, _T. dilatus_, and _T. nitidus_. Of the four, _T. dilatus_ appears to be completely allopatric in that it occurs at higher altitudes (above 2000 meters), whereas the other three occur below 1800 meters in the region (Davis and Dixon, 1965). In the Colima-Jalisco region, _Tomodactylus_ tends to occur higher (Dixon and Webb, 1966) than some of the _Syrrhophus_, but one subspecies of _Tomodactylus nitidus_ is a lowland frog, occurring sympatrically with the lowland _Syrrhophus modestus_. A similar situation is observed in Nayarit; the lowland _Tomodactylus_ occurs sympatrically with the small _Syrrhophus pallidus_. In both cases the _Syrrhophus_ is smaller than the _Tomodactylus_.

Frogs of the genus _Syrrhophus_ tend to occur at lower elevations than do their close relatives of the genus _Tomodactylus_ (Fig. 22). This generalization is complicated by the occurrence in the Sierra Madre Oriental in relatively high altitude _Syrrhophus_ (up to 2000 m.) and the occurrence in Michoacán of low altitude _Tomodactylus_ (to sea level). There are no _Tomodactylus_ in the Sierra Madre Oriental, whereas the genus _Syrrhophus_ is represented in the lowlands of western México (_modestus_ group). _Syrrhophus_ and _Tomodactylus_ exhibit essentially parapatric distributions. The two genera as now composed can be characterized as low to moderate elevation frogs (_Syrrhophus_) and moderate to intermediate elevation frogs (_Tomodactylus_).

LITERATURE CITED

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1958. A biogeography of reptiles and amphibians in the Gomez Farias region, Tamaulipas, Mexico. Misc. Publs. Mus. Zool. Univ. Michigan, 101:1-102.

MILSTEAD, W. M., J. S. MECHAM, and H. MCCLINTOCK