Color pattern.—As is evident in the diagnoses, the color patterns of given populations have been regarded as useful in separating the species and subspecies. Duellman (1958) suggested that the coloration, with the exception of modestus, was a dark ground color with pale markings. It is a moot point whether the frogs have light spots on a dark background or have a light background with an extensive reticulate dark pattern. The venters are gray or white, and the vocal sac is nearly black in some species. Interorbital dark bars or triangles are absent in only two species of the eastern complex, cystignathoides campi and marnockii; the latter lacks a supratympanic stripe, which is present in the other members of the eastern complex. Syrrhophus interorbitalis and nivocolimae have light interorbital bars; these bars occur in only one other population of the genus (S. c. cystignathoides). Bars on the thighs are ill defined or absent in the members of the marnockii and part of the modestus groups. The color in life is noted in the species accounts.

Voice.—The voices of all Syrrhophus can be described as a single short chirp or peep; without audiospectrographic analyses the significance of the differences between a chirp, peep, or short whistle cannot be appreciated. Martin (1958) and Wright and Wright (1949) reported multi-noted calls, and one collector of S. verrucipes noted the frog "trilled."

Fouquette (1960) presented analyses of two species (marnockii and pipilans nebulosus). The voices were very similar; both frogs were reported to "trill" and "chirp."

Systematic Account

The genus Syrrhophus has been defined (Lynch, 1968) and limited to the group of species occurring in Guatemala, México and the United States. The closest relatives of Syrrhophus are the frogs of the genus Tomodactylus (Dixon, 1957; Firschein, 1954). Lynch (1968) implied there were no osteological bases for the separation of Eleutherodactylus, Syrrhophus, and Tomodactylus. At that time, I believed such to be the case and derived Syrrhophus and Tomodactylus from the rhodopis complex of Eleutherodactylus, with which they share terrestrial habits and relatively short limbs. In the rhodopis complex there is a tendency for the loss of the outer palmar tubercle, a not uncommon condition in Syrrhophus and Tomodactylus.

However, the skulls of Syrrhophus and Tomodactylus show departures from the pattern observed in the Middle American Eleutherodactylus, as well as many of those species in western South America. Baldauf and Tanzer (1965) reported that the frontoparietals and prootics were fused in Syrrhophus marnockii and that the prootics and exoccipitals appeared to be one bone (otoccipital). The otoccipital is not uncommon in eleutherodactyline frogs, but the fusion of the frontoparietals with the prootics (regardless of the fusion of the latter with the exoccipital) is uncommon in the family. I have found the frontoparietal-prootic fusion only in Syrrhophus (all species), Tomodactylus (all species), and Eleutherodactylus (West Indies species). None of the Middle American Eleutherodactylus has the two bones fused. Examination of the character is difficult in dried skeletal preparations. Cleared and stained or macerated preparations are satisfactory for checking this character.

Thus, in addition to the presence of numerous plantar supernumerary tubercles in the frogs of the genera Syrrhophus and Tomodactylus, these two genera can be separated from other Middle American eleutherodactylines by the fusion of the frontoparietals and prootics. This character not only further strengthens the argument that the two genera are closely related but poses a problem of zoogeographic analysis of the distribution of the character, which will be discussed fully elsewhere.

Key to the Species of the Frog Genus Syrrhophus

1. Three large, well-developed palmar tubercles2
Two large palmar tubercles; outer (third) palmar tubercle reduced in size or absent9
2. Digital pads more than twice (usually three or more) times width of digit3
Digital pads less than twice width of digit4
3. Males having vocal slits; dorsum vermiculate; diameter of tympanum in males about one-half diameter of eye[S. dennisi]
Males lacking vocal slits; dorsum flecked, spotted, or blotched; diameter of tympanum in male about three-fourths that of eye[S. longipes]
4. First finger longer than second5
First finger shorter than or equal to second7
5. Venter smooth; dorsum spotted or vermiculate[S. leprus]
Venter areolate, or if smooth, dorsum flecked and interorbital bar lacking 6
6. Venter areolate; interorbital bar present; ground color yellowish[S. cystignathoides cystignathoides]
Venter smooth; interorbital bar absent; ground color brown[S. cystignathoides campi]
7. First finger shorter than second; digital tips only slightly dilated; green in life with darker green spots[S. verrucipes]
First finger equal to second; digital tips slightly to moderately expanded 8
8. Dorsum vermiculate; interorbital bar present; ground color cream to brown in life [S. guttilatus]
Dorsum punctate or flecked; interorbital bar absent; ground color green in life[S. marnockii]
9. Dorsum dark with pale (red in life) spots; digital pads not expanded[S. rubrimaculatus]
Dorsum pale with dark markings and digital pads slightly to widely expanded10
10. Digital tips not widely expanded; tympanum well-defined; outer metatarsal tubercle more than one-half size of inner11
Digital tips widely expanded, truncate in outline; tympanum poorly defined; outer metatarsal tubercle less than one-half size of inner12
11. Dorsum dark brown with large light spots or blotches; tympanum/eye ratio usually greater than 43 percent[S. pipilans pipilans]
Dorsum dark brown with small light spots; tympanum/eye ratio less than 48 percent[S. pipilans nebulosus]
12. Light interorbital bar present13
Light interorbital bar absent14
13. Adults small, less than 22 mm. snout-vent length with a broad mid-dorsal stripe; dark bands on shank narrower than light interspaces[S. nivocolimae]
Adults larger, more than 22 mm. snout-vent length; dorsum vermiculate; dark bands on shank broader than light interspaces[S. interorbitalis]
14. Dorsum spotted with discrete black spots; pattern definite[S. modestus]
Dorsum reticulate or vermiculate, pattern poorly defined15
15. Adults small, less than 21 mm. snout-vent length; upper arm not banded[S. pallidus]
Adults larger, usually greater than 21 mm. snout-vent length; upper arm banded[S. teretistes]

Species Accounts