A new species of Andean semiaquatic lizard of the genus Potamites (Sauria, Gymnophtalmidae) from southern Peru

Abstract We describe a new lizard species of the genus Potamites from the montane forests of the Cordillera de Vilcabamba (Cusco region) and Apurimac River valley (Ayacucho region), between 1500 and 2000 meters of elevation, in southern Peru. The new species is distinguishable from all other species of the genus mainly by having highly keeled scattered scales on dorsum and females lacking femoral pores.


Material and methods
The description format for the new species generally follows that of Uzell (1966), Vanzolini (1995) and Avila-Pires and Vitt (1998). For the comparisons, we used the descriptions from all Neusticurus and Potamites species known in the literature: data for most Neusticurus and Potamites were taken from Uzzell (1966), data for P. juruazensis was taken from Avila-Pires and Vitt (1998), for P. ocellatus from Vanzolini (1995), data of N. tatei from Barrio-Amorós and Brewer-Carias (2008) (for a detailed list of specimens reviewed see Appendix 1). Nomenclature of scale characters follows that of Uzell (1966) and Köhler and Lehr (2004). Scale sizes were measured using precision calipers and were rounded to the nearest 0.1 mm. For characters recorded on both sides, the condition on the right side is presented first. Everted hemipenes were fixed with formalin 3.7%. The abbreviation for the museum collection is CORBIDI (Cen-tro de Ornitología y Biodiversidad) and GPS coordinates were taken using the geodetic datum WGS84.
Potamites montanicola is easily distinguished of all other Potamites and Neusticurus species by having highly keeled scales scattered all over the dorsum (all species have either tubercles or keeled scales forming longitudinal rows from neck to the insertion of the hind limbs, or lack of them) and by females lacking femoral pores (only some female specimens of the type series in P. juruazensis lack femoral pores). Of all Potamites species, P. montanicola best resembles P. ecpleopus, P. juruazenzis and P. ocellatus. It differs from P. ecpleopus by having a lower number of keeled scales on dorsum (see specimens reviewed in Appendix 1): 32-37 (vs 36-45), a higher number of scales around midbody: 43-50 (vs 34-46), frenocular scale pentagonal (vs triangular) and a lower number of femoral pores bearing 19-21 in males and lacking in females (vs 25-48 in males and 1-15 in females). Differs from P. juruazenzis by having a higher number of scales around midbody: 42-50 (vs 31-40), bearing scattered dorsal highly keeled scales (vs bearing four longitudinal rows of dorsal tubercles), a higher number of lamellae of fourth toe: 22-27 (vs 16-22), a higher number of femoral pores in males: 19-21 (vs 10 -16) and by lacking femoral pores in females (vs 0-2 femoral pores). Differs from P. ocellatus by its smaller size: 68.6 mm as maximum SVL in males (vs 75 mm in P. ocellatus), dorsal highly keeled scales present (vs flat dorsal tubercles present), temporal region covered by medium size polygonal scales (vs covered by large scales interspersed with granules) and has a lower number of femoral pores in males: 19-21 (vs 41).  apodemus, 40-62 in N. bicarinatus, 58-64 in N. medemi, 62-72 in N. racenisi, 32-46 in N. rudis, 45-59 in P. strangulatus and 60-61 in N. tatei) and lacking femoral pores in females (femoral pores present in all Potamites and Neusticurus excepting some individuals of P. juruazensis).
The completely everted hemipenis is an acapitate organ without a medial welt; apex with two large protrusions separated by the distal end of the sulcus spermaticus; sulcus spermaticus single, flounces lacking calcified spines and forming two chevrons on distal half of hemipenis; sulcate flounces about as wide as asulcate flounces; asulcate flounces becoming shorter distally, five in the basal half and thirteen in each protru- sion, distal chevrons separated by a small expansion pleat; sulcus spermaticus single, flanked by a broad naked expansion pleat widened distally.
Coloration in preservative. Dorsal surface of head, dorsal surface of body, tail, limbs, hands and feet dark brown; lateral ocelli present in two pairs with a white rounded center; labial region, throat, chest and venter pale blue with scattered black blotches. Ventral surfaces of forelimbs pale yellow with black blotches; ventral surfaces of thighs pale brown with black blotches above position of femoral pores; ventral surfaces of hands and feet pale brown becoming darker at fingers III, IV and V; ventral surface of tail pinkish brown with diffuse black blotches.
Coloration in life (Fig. 1a-d). Dorsal and lateral surfaces, of the head dark brown; rostral and first supralabial scale same color as head; superior labium is bluish with dark spots from second supralabial; iris reddish gold; ventral surface of head, pregular and gular region black with pale blue irregular blotches. Dorsal surface of body same color as head, darker than flanks; lateral surface of body brown with a pair of black ocelli on both sides, before and after insertion of forelimbs, each ocelli bearing a white center, coinciding with a conical tubercle; tuberculate scales darker than granular scales; ventral surface of body same color as ventral surface of head. Limbs, similar to body, ventral surface of arms yellowish brown, ventral surface of legs creamy brown. Coloration of dorsal surface of tail like that of body, ventral surface of tail reddish brown, only red at the base and.
Variation (Fig. 1, d). In the type series, azygous scales (between frontonasal and prefrontal scales) are present in six specimens (CORBIDI 08324-28, 08335) including males and females, and are absent in five specimens (CORBIDI 06957, 08322, 08334, 08336, 08338); infralabials usually five, four present in CORBIDI 06957, 08324, 08327 and six in CORBIDI 08322, 08325; lateral ocelli are present in two pairs, first pair located anteriorly to the insertion of forelimbs and the second one posteriorly, the white spot at the middle of the ocelli includes usually one conical tubercle; with two conical tubercles at the right side in CORBIDI 08327 and at both sides in CORBIDI 08338. CORBIDI 06957, 08324, 08327, 08334-35 have more than two pairs of lateral ocelli and CORBIDI 08336, 08338 lack of lateral ocelli; in life, ventral coloration in males is usually pale blue, with black blotches in CORBIDI 08322, and yellow with black blotches in CORBIDI 08324, in females the throat and chest can be creamy white or dark brown, belly creamy white or darker bearing or lacking dark blotches. Sexual dimorphism is evident in females, because all of them are lacking femoral pores, furthermore other differences between females and males are the SVL (maximum SVL in females 56 mm, maximum SVL in males 68 mm) and the head width (Maximum head width in females 3.2 mm and maximum head width in males 13.23 mm). See Table 1 for variation in selected morphometric and squamation characters in the specimens examined.
Etymology. The specific epithet 'montanicola' is a compound from the spanish word "montano", adjective to describe something from a mountain, and the latin suffix "-icola" for "inhabitant" and refers to the montane forests where this species lives.  Distribution and natural history. Potamites montanicola is known from two localities in the Andes in southern Peru (Fig 5), both separated by 64 km air line and located at the Cordillera de Vilcabamba and Apurimac river valley, the known altitudinal range is between elevations 1570 and 2100 m. The holotype and most of the specimens of the type series were found on the sides of a stream, which were 3 meters wide with stones and rocks as substrate. The vegetation in the area was riverside vegetation mainly composed of: Miconia sp., Gordonia sp. and Guarea sp. and herbs from the family Rubiaceae and Melastomataceae. Climbers (vines and lianas) were diverse and relatively common and include species of the family Celatraceae, Polygalaceae and Campanulaceae. All individuals were found perching on rocks and stones at sides of the stream at night. In some cases, individuals were observed swimming in the middle of the stream, or using the stream to escape. No other lizard species were recorded at the type locality, but on the same stream we observed the vipers Bothriopsis taeniata and Lachesis muta. Amphibians also reported here include Hypsiboas balzani, Hyalinobatrachium bergeri, Osteocephalus mimeticus, Pristimantis rhabdolaemus and Pristimantis mendax. The second locality where P. montanicola was collected (specimen CORBIDI 06957) is a secondary forest, close to the Chiquintirca -Cajadela road. In this site, arboreal vegetation includes species of Cecropia sp., and abundant bushes. The specimen CORBIDI 06957 was found during the day near a creek with substrate mainly composed of leaf litter and fallen trunks. In this locality, P. montanicola is sympatric with the tropidurid lizard Stenocercus torquatus and the anurans Hyalinobatrachium bergeri, Hypsiboas balzani, Pristimantis mendax and Pristimantis rhabdolaemus. No snakes were reported.
Remarks. The genus Potamites is composed of species that are primarily lowland distributed. One of these, P. ecpleopus, has the largest distribution range in Potamites (despite its unclear taxonomy). Sinitsin (1930) assigned the populations of Potamites in Perené and Chanchamayo valleys, central Peru, as paratypes of P. ocellatus, but later, Vanzolini (1995) assigned them as part of the Potamites ecpleopus complex and not as P. ocellatus sensu stricto. P. ocellatus was then validated and redescribed from only one specimen from El Beni, Bolivia (Vanzolini 1995). These taxonomic uncertainties render the species assignment of the populations from Chanchamayo and Perené unclear. Several surveys to Chanchamayo and Perené from 2008 to 2010 by the senior author resulted in unsuccessful efforts to find the populations mentioned by Sinitsin (1930). Even though P. montanicola most northern locality (Cajadela Community) is 250 Km air line from Chanchamayo and Perené valleys, P. montanicola has a higher vertical distribution range than those populations (by 1000 m). This evidence, along with morphological characteristics, distinguish and validate P. monticola as distinct. Furthermore, P. montanicola is the only species described for Peru that occurs above 2000 meters of elevation and to be reported as exclusive from montane forests. Further studies on the taxonomic identity and the populations of P. ecpleopus would help to clarify their status and to determine if they belong to a described or undescribed species.