Pristimantis stipa is a robust bodied frog with a snout-vent-length ranging from 15.6-24.4 mm for males, and 35.1 mm for females. The head is narrow and wider than it is long, though it is not as wide as the body. The snout is short and round at both lateral and dorsal views. The canthus rostralis (or rostral crest) appears somewhat curved in profile view but straight at dorsal view. The tympanic annulus, though present, is weakly defined. Tympanic membrane is present and distinct. A large thick fold over the tympanum partially obscures its edges on the posterodorsal sides. The tympanic membrane diameter is 35.8% that of the eye diameter. Upper eyelid lacks nodules. The dorsum is fairly smooth. The ventral side of the thighs, belly, chest, and throat are not as smooth as the dorsal surface and are a little more granular. The dorsolateral fold is distinct, thick, and discontinuous. The hind limbs are slender. The heel and the outer surfaces of the tarsus lack tubercles. A short, inner-tarsal ridge is present. The inner metatarsal is prominent, elliptical and twice as large as than those in the low tubercles. The toes lack lateral fringes and webbing. Both fingers and toes have narrow discs with rounded tips and the discs on the toes lack circumferential grooves. The relative toe lengths are: 1<2<3>5<4. Toe III is a little bit longer than toe V. Vocal slits are absent on males. Males also have nuptial pads on dorsal and medial surfaces of the thumb (Venegas and Duellman 2012).
The following features differentiate P. stipa from the rest of the species in Pristimantis, including the 15 assigned to the P. orestes group (with the exception of P. simonsii): P. stipa has a smooth dorsum, the discs on the fingers and toes are narrow and lack marginal grooves, and ulnar nodules form a low fold. P. stipa can be easily distinguished from P. simonsii by the following characteristics: prominent dentigerous processes of vomers (which are absent in P. simonsii), both the tympanic annuls and tympanic membrane are distinct (they are absent in P. simonsii), and toe V is just a bit shorter than toe III (in P. stipa, toe V and toe III are just about the same length). Because P. stipa lacks marginal grooves on the discs of the toes and fingers, it can be confused with Phrynopus, of which one species, P. thompsoni, is also found. However, P. thompsoni has rows of small swellings on the dorsum, both the tympanic membrane and the tympanic annulus are absent, fingers I and II are the same length, and the venter is tan with lighter brown spots (Venegas and Duellman 2012).
Coloration in life: In the female holotype, the dorsum is homogenously brown. The groin, posterior and anterior surfaces of the thighs, and dorsal surfaces of the feet are a darker shade of brown decorated with dull white blotches. The venter is a dark brown with white spots. The iris is grayish-white with a network of thin, brown lines. Males have brownish cream mottling on their throats while the same mottling on females is white (Venegas and Duellman 2012).
Coloration in preservation: In ethanol, the coloration is the same as the live holotype. The only difference is that dark shades of brown are now simply light brown and the dull white blotches are now solid white (Venegas and Duellman 2012).
Variation: Females are larger than males. Both the morphology and the coloration of the paratypes are identical to the holotype (Venegas and Duellman 2012).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Peru
P. stipa has been found only at the type locality in northwestern Peru, in humid high-elevation montane puna grassland above tree line at 3596 m above sea level. This species occurs in the same habitat as P. mariaelenae (Venegas and Duellman 2012).
Trends and Threats
Habitat destruction, especially through deforestation, agriculture, and environmental contamination, is the main threat to strobomantid frogs, according to Duellman and Lehr (as cited in Venegas and Duellman 2012). This species inhabits puna habitat, grasslands that are slow to recover, which are especially sensitive to overgrazing by cattle. The recent pressure for mineral exploration means a high probability of future mining in the area, which is also likely to be a big threat (Venegas and Duellman 2012).
The species name is based on the generic name of the feather grass that is common at the type locality.
Venegas, P. J., and Duellman, W. E. (2012). ''Two syntopic new species of the Pristimantis orestes Group (Anura: Strabomantidae) from northwestern Peru.'' Zootaxa, 3249, 47-59.
Written by Adolfo Ivan Gomez (adolfoivangomez AT gmail.com), Museum of Vertebrate Zoology, UC Berkeley
First submitted 2012-11-02
Edited by Michelle S. Koo (2012-11-17)
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