In preservative, head and dorsum yellowish brown; dark brown stripe from nostril to eye; dark brown spots on snout; a dark brown interorbital triangle with apex directed backward; dark brown supratympanic region; dorsal stripes same as in living individuals; flanks pale yellow with brown spots in some specimens; groin creamy white; thighs and shanks having or lacking transverse dark brown blotches; spaces between blotches creamy white or yellow-brown; arms pale yellowish brown; belly and vocal sac creamy white.
Variation.—Geographic variation in size and some proportions, such as the ratio of tibia length to snout-vent length and the ratio of the diameter of the tympanum to that of the eye, have been observed in this species. The largest individuals are from the Golfo Dulce region (samples from Piedras Blancas and Rincón de Osa), Puntarenas Province, Costa Rica. The smallest individuals are from El Recreo, Zelaya Province, Nicaragua, and from the Caribbean lowlands of Costa Rica.
The diameter of the tympanum is proportionately larger (relative to the size of the eye) in males from Tilarán, Guanacaste Province; the tympanum is nearly as large in males from Piedras Blancas, Puntarenas Province, and Puerto Viejo, Heredia Province, Costa Rica. The lowest ratios occur in individuals from Almirante, Bocas del Toro, Panamá, in specimens from the Caribbean lowlands of Costa Rica (except Puerto Viejo), and in those from El Recreo, Zelaya Province, Nicaragua. In general, the tympanum is proportionately larger in females than in males; the tympanum is largest in females from the Pacific lowlands of Costa Rica (Table 5).
Color variation has been observed in individuals from the same population, as well as in individuals from different localities, between males and females, and from night to day. In life, most individuals from the Pacific lowlands of Costa Rica are dark tan to greenish gray above with dark brown longitudinal stripes that are entire or broken, but some specimens (mostly males) are dusky brown and lack longitudinal stripes or an interorbital triangle; females usually have the dark interorbital triangle and the stripes on the dorsum. Individuals from Turrialba, Cartago Province, Costa Rica, are pale olive-tan with olive-brown markings. Individuals from Puerto Viejo, Heredia Province, Costa Rica, are uniformly yellowish brown with or without dark longitudinal stripes. Specimens from El Recreo, Zelaya Province, Nicaragua, are like those from Puerto Viejo. Males from Almirante, Bocas del Toro, Panamá, are pale brown with dark brown longitudinal stripes and an indistinct interorbital triangle. Females have a distinct interorbital triangle and dark brown blotches on the thighs and shanks.
By night, the dorsum usually is pale yellow, and the belly is creamy white. By day, the dorsum is dark tan; the stripes and spots are darker, and the belly is yellowish white. Taylor (1952) noticed that considerable variation in color pattern occurred from night to day in individuals from Turrialba, Cartago Province, Costa Rica. At night some individuals lacked a dorsal pattern, but by day many of these individuals developed dorsal stripes.
Cranial Osteology.—The skull of Hyla elaeochroa is slightly wider than it is long, and flat. The premaxillary is small and bears 10 to 15 teeth (mean for 9 specimens, 12.3). The alary process of the premaxillary is small, vertical, and slightly concave posteriorly. Ventrally, the premaxillary is partially united to the prevomer by ossification. The maxillary is slender and bears 70 to 82 teeth (mean for 9 specimens, 74.3). The pars facialis of the maxillary is laterally convex and is about twice as high as the pars dentalis.
The nasal is large, robust, anteriorly truncate, but pointed posteriorly in dorsal view. The nasal comprises about 45 per cent of the total length of the skull. There is an anterior cartilaginous septum nasi separating the two nasals; the latter overlap the sphenethmoid posteriorly. Each nasal bears a shallow concavity in the midlateral side and lacks a maxillary process. Dorsally, the sphenethmoid is wider than long, roughly pentagonal in shape; the frontoparietal is elongate, smooth, and bears a small anterior supraorbital process. The sphenethmoid and frontoparietal form the anterior margin of the frontoparietal fontanelle; the fontanelle is narrow anteriorly and wider posteriorly (Fig. 5B).
The entire distal surface of the proötic is in contact with the posterior arm of the squamosal. A narrow cartilaginous crista parotica is visible dorsally in some specimens. The squamosal is broad posteriorly but its anterior arm is slender and not in contact with the maxillary.
Table 5.—Geographic Variation in Size and Proportions in Males of Hyla elaeochroa.
(Means in parentheses below observed ranges.)
| Locality | N |
Snout-vent length (mm.) |
Tibia length/ snout-vent |
Tympanum/ eye |
Foot length/ snout-vent |
| Nicaragua: El Recreo | 9 |
28.0-30.3 (29.3) |
0.51-0.57 (0.55) |
0.47-0.59 (0.51) |
0.39-0.54 (0.41) |
| Costa Rica: Tilarán | 21 |
28.8-33.6 (30.6) |
0.47-0.57 (0.52) |
0.48-0.65 (0.59) |
0.40-0.46 (0.41) |
| Costa Rica: Puerto Viejo | 22 |
26.3-32.4 (29.7) |
0.49-0.54 (0.52) |
0.48-0.65 (0.57) |
0.38-0.45 (0.42) |
| Costa Rica: Turrialba | 95 |
28.1-35.0 (30.6) |
0.47-0.56 (0.51) |
0.47-0.68 (0.56) |
0.37-0.46 (0.41) |
| Costa Rica: Bataán, Limón, and Suretka | 26 |
26.3-32.7 (30.0) |
0.47-0.54 (0.51) |
0.45-0.66 (0.50) |
0.36-0.44 (0.41) |
| Costa Rica: Piedras Blancas | 21 |
33.3-37.7 (35.2) |
0.50-0.54 (0.51) |
0.48-0.64 (0.57) |
0.40-0.46 (0.43) |
| Costa Rica: Rincón de Osa | 24 |
31.4-35.9 (34.1) |
0.50-0.56 (0.53) |
0.45-0.61 (0.54) |
0.40-0.46 (0.43) |
| Panamá: Bocas del Toro | 6 |
31.0-33.5 (32.1) |
0.49-0.54 (0.51) |
0.47-0.50 (0.48) |
0.41-0.43 (0.42) |