Description.—Head flat, especially in females, longer than wide; snout long, protruding beyond mouth; loreal region concave; canthus ill-defined; length of eye greater than internarial distance or width of eyelid; length of eye less than interorbital space; tympanum distinct; interorbital spot irregular; supratympanic fold faint; arms short; fingers free of webs; discs on third and fourth fingers equal to diameter of tympanum; inner metatarsal tubercle on base of first finger distinct; first finger shorter than second; palmar tubercle distinct (Fig. 1C); legs short (usually less than 50 per cent of snout-vent length); tarsal fold absent; metatarsal tubercles small, outer tubercle smaller than inner; subarticular tubercles small, simple, distinct; toes less than half webbed (Fig. 1D); skin smooth above with a few small pustules on head, scapular region, flanks, and supratympanic region; arms and legs smooth; skin of belly coarsely granular; posteroventral surfaces of thighs finely granular; tongue small, rounded, longer than wide, slightly free and notched posteriorly; vocal slits small, lateral to tongue; choanae moderate in size.
Variation.—The largest males of Hyla staufferi are from Jalapa, Guatemala, and from San Salvador, El Salvador. In these samples the average snout-vent length is 27 mm. In Panamanian specimens the average snout-vent length is 23.6 mm. Slight variation in the ratio of tibia length to snout-vent length exists throughout the range; more variation exists in the ratio of the diameter of the tympanum to that of the eye; the tympanum is proportionately larger in northern populations (Table 7). The primary differences between Panamanian and more northern populations are in size, color pattern on the dorsum and shanks, amount of webbing between the toes, and duration of notes in the mating call (Table 2, Pl. 4).
The color in Panamanian staufferi is gray or gray-brown with a pair of distinct, complete, dark brown dorsolateral stripes, a pair of entire paravertebral stripes, and in some specimens a vertebral stripe. About five per cent of the individuals have interrupted stripes on the dorsum, whereas in the more northern populations complete paravertebral stripes are present in less ten per cent of the specimens; when complete stripes are present, they are irregular. The dorsal ground color in non-Panamanian specimens is brown, olive-brown, or dark brown.
Transverse bars are present on the shanks in Hyla staufferi from Costa Rica northward to México, whereas in Panamá all the individuals have a longitudinal stripe on the shank (Table 7, Pl. 2). The interorbital spot or bar is more noticeable in northern populations than in specimens from Panamá. Frogs from Costa Rica and northward have the toes about three fourths webbed, whereas in Panamá the toes are about two fifths webbed. The mating calls of the northern and Panamanian populations are similar, but the notes have a longer duration in the northern populations and a higher dominant frequency in Panamanian populations.
Hyla staufferi is the most variable member of the Hyla rubra group in Central America. The Panamanian populations are geographically separated from the Costa Rican and more northern populations by an area of tropical rainforest in the Golfo Dulce region in southeastern Costa Rica and adjacent Panamá. Hyla staufferi does not occur on the Caribbean versant of Costa Rica and Panamá. The Golfo Dulce region and the Caribbean versant are humid and inhabited by Hyla elaeochroa. Hyla staufferi is an inhabitant of subhumid and xeric areas.
On the basis of the discontinuous variation in several characters which correlate with the disjunct distribution of the two populations, two subspecies of Hyla staufferi are recognized. The accounts that follow apply equally to each.
Cranial Osteology.—The skull of Hyla staufferi is flat and longer than wide. The premaxillary is small and bears 9 to 13 teeth (mean for 5 specimens, 11.3). The alary process of the premaxillary is small, concave posteriorly and vertical. Ventrally, the premaxillary is united to the prevomers by partially ossified cartilage. The maxillary is slender and usually bears 49 to 70 teeth (mean for 5 specimens, 60.7). The pars facialis of the maxillary is convex and less than twice the height of the pars dentalis.
The nasal is large, rounded anteriorly, and pointed posteriorly in dorsal view. The nasal comprises about 40 per cent of the total length of the skull. Anteromedially the two nasals converge; posteriorly they overlap the sphenethmoid. The nasals lack a concavity in the midlateral surface. Dorsally, the sphenethmoid is wider than long, roughly pentagonal in shape; the frontoparietal is elongate, narrow, and smooth, with a small supraorbital process anteriorly. The frontoparietal fontanelle is narrow anteriorly and wide posteriorly.
Table 7.—Geographic Variation in Size and Color in Males of Hyla staufferi.
(Means in parentheses below observed ranges.)
| Locality | N |
Snout-vent length (mm.) |
Complete dorsal stripes (per cent) |
Barred shanks (per cent) |
| Veracruz | 47 |
23.0-27.3 (25.4) | 0.0 | 100 |
| Campeche | 20 |
24.6-27.5 (25.5) | 0.0 | 100 |
| Oaxaca | 75 |
24.0-28.7 (26.4) | 9.3 | 100 |
| Chiapas | 20 |
23.2-27.8 (25.5) | 10.0 | 100 |
| Guatemala | 22 |
25.0-29.0 (26.9) | 10.9 | 100 |
| El Salvador | 21 |
24.7-28.6 (27.0) | 0.0 | 100 |
| Honduras | 34 |
20.6-27.0 (24.9) | 3.3 | 100 |
| Nicaragua | 67 |
21.5-26.8 (24.9) | 3.0 | 92.7 |
| Costa Rica | 54 |
20.7-26.6 (24.2) | 5.5 | 98.1 |
| Total Non-Panamanian | 360 |
20.7-29.0 (25.9) | 5.4 | 98.3 |
| Panamá | 72 |
21.7-26.0 (23.6) | 94.5 | 0.0 |