Comprehensive DescriptionRead full entry
Diagnosis:Females are large-sized (50-70 mm SVL) and males (30-43 mm SVL) are moderate-sized. This species has a well developed pair of parallel suprascapular plicae (dorsal ridges) that run to about midbody. It also has paired laterosacral ridges on the posterior dorsum that form a V-shape in Nicaraguan, Honduran, and Costa Rican populations, but consist of two non-converging parallel ridges in populations from western Panama. A dark seat patch is present on the posterior thigh surface and may be uniform with yellow spots or mottling (Savage and Myers 2002; Cope 1875).
Description:Craugastor megacephalus is a leaf-litter dwelling frog. The SVL of a male adult frog is 30 to 43 mm, and the SVL of a female adult frog is 50 to 70 mm. Snout is truncated in dorsal view and slightly obtuse in lateral view. Nares do not protrude. Upper eyelid is tuberculate. Tympanum is large. Vomerine odontophores are triangular in shape, and located posterior to the choanae with odontophore patches separated by a narrow medial gap. Large cranial ridges are present with knobs or bosses on the posterior end of the crests. These knobs are particularly evident on large females, above the supratympanic fold. This species has a set of chalice-shaped or hourglass-shaped plicae (dorsal ridges); parallel suprascapular plicae run to about midbody, and paired laterosacral ridges form either a V-shape or parallel lines on the posterior dorsum. The V-shape of laterosacral plicae is found in Nicaraguan, Honduran, and Costa Rican populations, while laterosacral plicae consisting of non-converging parallel ridges occur in populations from western Panama. Paravertebral plicae are absent. The dorsum of adults is smooth to shagreened with a few scattered, low pustules. Pustules present in juvenile Craugastor megacephalus are small with pale tips and usually pointed. The venter is smooth. One or two large tubercles are present on the heel. Tarsal fold is lacking. Juveniles have prominent tubercles on the outer tarsus, but tarsal tubercles are weakly developed in adults (Savage and Myers 2002).
The dorsal surface of Craugastaor megacephalus is gray-tan to olive-brown, sometimes with a salmon cast. Large females especially may be dark brown. Individuals have black supratympanic folds (usually), a black spot on the tympanum (usually), black plicae, black sacral spots and enlarged sacral tubercles, and an indistinct lighter interorbital bar or blotch, bordered by slightly darker markings. Juveniles have a lighter ground color which makes the dark markings stand out more in constrast. Upper lip may have a lighter stripe, alternating dark and light bars, or uniform coloration. Lower orbit usually has adjacent alternating black and off-white spots. No paired dorsal stripes are present. Dorsal limb surfaces may be uniform or may have indistinct darker bars. Posterior thigh is dark brown to black and may be uniform or spotted or mottled. The posterior black seat patch is continuous with a black base that continues onto the undersurface of the thigh. On the ventral surface, the throat and chest are covered by a brown reticulum with large round light spots in juveniles and larger round dark spots in adults. Juveniles also have a series of lighter spots along the edge of the lower jaw. In Costa Rican C. megacephalus, the iris is black flecked with gold, while in Panama the iris may be bronze to brown, sometimes lighter in the lower half, rarely with greenish bronze tint, and with black venation or suffusion (Savage and Myers 2002).
Juveniles from Costa Rica have yellow-orange to red-orange on concealed limb surfaces, on the posterior venter, and ventral surfaces of hands and digits (while the soles are brown). One juvenile from Panama had bright greenish yellow on all ventral surfaces (Savage and Myers 2002).
This species was partitioned out from E. biporcatus, with other populations assigned to E. rugosus and E. opimus. It may still be a species complex, given the different juvenile coloration of Costa Rican vs. Panamanian specimens, and the different configuration of the laterosacral plicae in populations from Bocas del Toro, northwestern Panama (Savage and Myers 2002).
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).