Smilisca sordida, or the Drab Treefrog, is a small frog with the size varying from 36.2 mm for males to 56.3 mm for females (Duellman 2001). The head is longer than it is wide. Individuals from the Caribbean lowlands have dull and round snouts, while those from the Pacific Lowlands have longer and more pointed snouts. Those observed from the Meseta Central have snout shapes in between those of the Caribbean and Pacific populations (Duellman 2001). Eyes are moderately sized, and the distinct tympanum has a diameter of one-half the diameter of the eye (Savage 2002). A supratympanic fold extends from behind the eye and over the tympanum, and is bordered by a dark line. (Guyer and Donnelly 2005). The lips are slim and flared. The tongue is ovoid and somewhat notched posteriorly. Vomerine tooth patches are on elevated, almost transverse ridges between ovoid to elliptical choanae (McCranie and Wilson 2002). The skin on the throat and chest is coarse and the skin on the belly and ventral surface of the thighs is roughly areolate. (McCranie and Wilson 2002). Warts are present along the posteroventral border of the lower arm (Savage 2002). The fingers are small and stout and finger discs are large. The fingers are one-half webbed and the toes are four-fifths webbed. Both fingers and toes have expanded discs (Duellman 2001). The relative length of fingers is III>IV>II>I. Webbing is basal between fingers I-II, with the remaining webbing formula being II 1-2 1/3 III 2--1 IV. (McCranie and Wilson 2002). The relative length of the toes is IV>III=V>II>I, with the webbing formula for the feet being I 3 / 4-1-II 3 / 4-1 III 3 / 4-1 IV 1-3 / 4 V (McCranie and Wilson 2002). The toe discs are broadly expanded and only slightly smaller than the toe discs on the fingers. The disc covers on the toes are even, and the disc pads on toes broadened. Lateral keels are present on the unwebbed portions of the toes (McCranie and Wilson 2002). This species has an oval-shaped, flat, and elongated inner metatarsal tubercle. (Duellman 2001). Males have paired vocal slits and a light brown nonspinous nuptial pad on the base of each thumb (Savage 2002).
This frog has a gray-brown to tan dorsum, a white ventrum, and a deep purple groin. There is a poorly distinguished black mask around its eyes. (Guyer and Donnelly 2005). Smilisca sordida has weak crossbands on its back legs, as well as dark spots on the head and back (Leenders 2001). The posterior of the thigh is deep purple with small blue, green or tan flecks. Breeding males have a white vocal sac (Duellman 2001). This species has a yellowish brown iris with black net-like veins (Guyer and Donnelly 2005).
The larval body is moderately sized and reaches approximately 32 mm in length. The caudal musculature is beige with light red specks which vary from dark to light areas along the midline. The body is ovoid, the mouth ventral, and the nostrils and eyes are dorsolateral. The large, entire oral disc has well developed beaks with two-thirds denticle rows. The beaks are bluntly serrate and the papillae are in two rows which are sideways and ventral to the mouth. There are numerous extra rows at the corner of the mouth, but none higher than the mouth. The spiracle is lateral and sinistral. The vent tube is dextral. The tail is moderate in length and pointed, with moderately-sized caudal fins (Savage 2002).
The tadpole body is beige and the belly is pale beige with a silver or white tint. The iris is bronze (Savage 2002).
Smilisca sordida is easily confused with two other Smilisca species (Guyer and Donnelly 2005). It is distinguished from Smilisca phaeota by the absence of a white stripe on its upper lip, and it does not have the spot beneath its eye that is characteristic of Smilisca baudinii (Leenders 2001) . Duellman states that specimens taken from Honduras and Nicaragua are like those from the Meseta Central in Costa Rica, having bluish white mottling on the posterior flank and lacking light specks on the posterior surfaces of the thighs. These specimens are smaller and modestly different from those in the Pacific versant in Costa Rica, and indicate that the latter may represent a species different from Smilisca sordida (Duellman 2001).
A Spanish-language species account can be found at the website of Instituto Nacional de Biodiversidad (INBio).