Description: Adult males measure 39-49 mm in SVL; adult females measure 46-55 mm in SVL. Head is equally wide as long. Snout is rounded to nearly semicircular in dorsal view, and rounded in lateral view. Eyes are moderately-sized. Tympanum is distinct, with a diameter 2/5 to 1/2 that of the eye. Fingers are short and robust with moderately sized discs. The width of the disc on Finger III is equal to the diameter of the tympanum. Fingers have moderate webbing, with only vestigial webbing between Fingers I and II. The distal subarticular tubercle under Finger IV is usually single but can sometimes be bifid. The thenar pad is substantially enlarged. No palmar tubercle is present. Toes have extensive webbing. The inner metatarsal tubercle is moderately sized, elliptical in shape, and low. The outer metatarsal tubercle is small or absent. A weak inner tarsal fold is present, as well as a distinct fleshy flap on the heel. Dorsal surfaces are smooth and the venter is granular. Males have a protuberant prepollex with a spine, in a retractable fleshy sheath; in contrast, females have a prepollex that is reduced to a nub. Adult males also have paired vocal slits and a single moderately distensible subgular vocal sac (Savage 2002).
Coloration in life (adults): Lime green to bluish green dorsal surfaces, with scattered melanophores and (usually) white or light bluish spots. Sometimes a light stripe is present from the tip of the snout to the flank. Flanks are yellowish olive green. Groin may be pale blue, bluish green, or red. Limbs are not barred. Anterior and posterior thigh surfaces are green to bright red. Digital webbing is orange to bright tomato red. Throat and ventral surfaces of limbs are green. Venter is cream (Savage 2002).
Coloration in life (juveniles): shading from lime green at the anterior to yellowish green at the posterior, with a narrow red dorsal line running from the tip of the snout over the upper eyelid down to the level of the vent, on each side, and a broad lateral yellow stripe running along each flank. Limbs are green, with no red markings. Digital webbing of juveniles is red-orange. Iris is silvery bronze (Savage 2002).
Similar species: Can be distinguished from H. palmeri by lack of a heel calcar (vs. present in H. palmeri; and from H. rosenbergi by coloration (H. rosenbergi is tan to gray dorsum, often with a mid-cephalic dark stripe and dark vertical lines on flanks) and lack of finger webbing between Fingers I and II (vs. webbing clearly present in H. rosenbergi) (Savage 2002).
Larval morphology: By stage 25, the body has a depressed, posteriorly truncated oval shape. The snout is rounded to truncated, whether viewed dorsally or laterally. Nares are midway between the eyes and the tip of the snout. In small larvae, the spiracle is sinistral and is pear-shaped but not strongly pigmented; at later stages, the spiracle enlarges and becomes hose-shaped (Fig. 2h and i). The anal tube is long and the opening is slightly on the dextral side. The mouth is ventral with a wide oral disc. The mouth is bordered by a large number of papillae except for a broad gap on the upper lip. Papillae are arranged in a single row on the dorsolateral part of the mouth, while the the ventrolateral and ventral lip areas are surrounded by a double row of papillae. The number of papillae increases from about 30 at larval stage 25 to about 150 papillae at larval stage 38.. LTRF is 2/4. Both upper and lower beaks are pigmented and serrated, with the upper beak being W-shaped and the lower beak V-shaped (Hoffman 2005).
Larval coloration: The body has dark marbling. The dorsum has punctate dermal melanophores, while the ventrolateral parts of the body have dispersed basket-shaped melanophores. Fine silvery shiny iridophores are present in groups on most of the dorsum, the eyeballs, and the ventrolateral parts of the body. The ventral thorax has dense pigmentation laterally, but the center of the thorax has only a few dispersed melanophores. The abdomen is almost completely transparent, with the liver being orange-colored (Hoffman 2005).
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).
Species authority: Fouquette (1961).
The karyotype is 2n=24 (Duellman 1967).