Nannophrys guentheri Boulenger 1882

Males to 28.5 mm SVL, females not known. Head slightly wider than long. Snout rounded when viewed from above, truncate to rounded in profile. Nostrils closer to snout tip than to eyes, on slightly raised nasal prominences, but not as terminally located as in N. ceylonensis. No internasal, longitudinal groove present. Nasal capsules not elevated. Canthus rounded. Upper lip barely flared. A bony prominence is present anterior to the corner of the mouth. No dentigerous processes on mandible (present in N. ceylonensis). Tympanum distinct, circular, small to moderate in size, and set obliquely; tympanum is smooth and lacks tubercles. Finger and toe tips slightly pointed in adults. Finger II subequal to Finger IV, both just shorter than Finger III. Toes basally webbed. Inner metatarsal tubercle elongate but indistinct; outer metatarsal tubercle is lacking. Skin has dense, coarse warts, lacking white tips. The largest pustules are on upper eyelids and flanks; some pustules are paired, around the midline, the interorbital space, and on the posterior sacrum. Ventral surfaces are smooth, with males apparently lacking pectoral patches of white-tipped tubercles. Skin not co-ossified to skull. When hindlimbs are adpressed, the heels overlap (vs. heels meeting in N. ceylonensis). Skulls have minor evidence of exostosing (slight roughness) on the nasals only, and lack the heavy secondary ossification found in specimens of N. ceylonensis (Clarke 1983). See Comments section for further discussion of the characteristics differentiating N. guentheri from N. ceylonensis.Some questions have been raised as to whether this species is distinct from N. ceylonensis, an extant species (Stuart et al. 2008). Clarke (1983) thought that the two species were clearly distinct based on his examination of the type series of N. guentheri, both in morphology and osteology. Clarke (1983) also remarks that Kirtisinghe (1957) apparently confused N. guentheri with juvenile N. ceylonensis, and points out that Kirtisinghe's figure 36 lacks densely pustular skin and seems to have a longitudinal internarial groove, lacks a flared upper lip, lacks a bony prominence anterior to the corner of the mouth, has a short Finger IV, has heels meeting when hindlimbs are adpressed, and shows the dorsal pattern of a juvenile N. ceylonensis. See Clarke (1983) for detailed descriptions of the body and osteology of N. guentheri in comparison to those of N. ceylonensis.

This species was endemic to Sri Lanka and is known only from the general type locality "Ceylon". The exact habitat that this species required is not known (Stuart et al. 2008).

This species is known only from the type series of five specimens, collected more than 100 years ago. It has not been rediscovered despite extensive searches and is presumed extinct. Breeding is believed to have taken place on wet rocks near streams, as is the case for other members of the genus Nannophrys (Stuart et al. 2008).

The exact reasons for this species' extinction are not known (Stuart et al. 2008). Much of Sri Lanka's forest cover has been cut down, so habitat loss was potentially a major factor in the decline of this species.