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Stenocercus nigrocaudatus sp. nov. Figures 6–7 Holotype. CORBIDI 19768, an adult male from San Lorenzo, San José de Lourdes (5º4’33.16”S, 78º52’53.749”W, 1,892 m), San Ignacio Province, Cajamarca Department, Peru, collected by P.J. Venegas on 5 September 2018. Paratypes (8): CAJAMARCA DEPARTMENT: San Ignacio Province: CORBIDI 4387, an adult male from Tabaconas (5°14’8.16”S, 79°5’56.58”W, 1,716 m) collected by Maik Dobiey in August 2008; CORBIDI 4388-90, adult females, from Namballe (5°11’40.139”S, 79°4’49.738”W, 1,716 m) collected by M. Dobiey in August 2008; CORBIDI 19765-66, adult females, and CORBIDI 19767 and 19769, adult males, from San Lorenzo, San José de Lourdes (5°4’33.16”S, 78°52’53.749”W, 1,892 m), collected by P.J. Venegas on 5 September 2018. Diagnosis. Among the 80 species of Stenocercus (including the four species described herein), S. nigrocaudatus sp. nov. is only similar to species with granular scales on posterior surface of thighs, relatively short tail, caudal scales spinose, and two caudal whorls per autotomic segment; such as S. asenlignus sp. nov., S. arndti, S. qalaywasi sp. nov., S. flagracanthus, S. leybachi sp. nov., S. bolivarensis, S. carrioni, S. chlorostictus, S. crassicaudatus, S. empetrus, S. eunetopsis, S. torquatus and S. simonsii. Adult males of S. nigrocaudatus can be easily distinguished from the aforementioned species by a contrasting black tail with scattered turquoise flecks (Fig. 7C). Moreover, S. nigrocaudatus can be readily distinguished from S. qalaywasi, S. leybachi, S. bolivarensis, S. carrioni, S. chlorostictus, and S. eunetopsis by having granular scales on dorsal surface of neck (keeled in the compared species).Furthermore, S. leybachi possesses a distinct serrate low crest on neck (absent in S. nigrocaudatus), S. bolivarensis strongly keeled scales on flanks (granular), S. qalaywasi a distinct complete middorsally black antehumeral collar and two black nuchal bands (incomplete and absent, respectively), S. carrioni and S. chlorostictus by having strongly keeled dorsal scales on body (smooth and feebly keeled), and S. eunetopsis by having a longer tail with 62–66% of total length (50–55%). In addition, S. nigrocaudatus possesses more vertebrals (96–108) than S. carrioni (55–72), S. chlorostictus (63–73), and S. eunetopsis (59–80). Stenocercus nigrocaudatus shares with S. asenlignus, S. arndti, S. flagracanthus, S. crassicaudatus, S. empetrus, S. torquatus, and S. simonsii the presence of granular scales on neck. Nevertheless, the new species can be differentiated from these species by the coloration pattern, number of scales, or the length of tail. Adult males of S. arndti are easily distinguished from S. nigrocaudatus (state of character in parentheses) by having a bold black transverse band at midbody that extends ventrolaterally (bands on body absent); adult males of S. empetrus have the belly black (cream); S. simonsii has distinct black bands on body in both sexes (absent). Additionally, S. nigrocaudatus has a greater number of vertebrals (96–108) than S. arndti (74–94), more subdigitals (26–31) than S. empetrus (17–24), and a shorter tail in relation to the total length (50–55%) than S. simonsii (57–63%). Stenocercus asenlignus and S. flagracanthus differ from S. nigrocaudatus in having dorsal scales on the posterior half of body strongly keeled and mucronate (feebly keeled in S. nigrocaudatus). Moreover, adult males of S. asenlignus and S. flagracanthus have black bands on the body (absent in S. nigrocaudatus). Stenocercus crassicaudatus has a longer tail (57–62% of total length) than S. nigrocaudatus (50–55%). Adult males of S. torquatus differ from S. nigrocaudatus in having the antehumeral black collar complete middorsally and two distinct black nuchal transverse bands, whereas the new species has the antehumeral collar incomplete middorsally and lacks nuchal bands. Characterization. (1) Maximum SVL in males 72 mm (n = 4); (2) maximum SVL in females 76 mm (n = 5); (3) vertebrals 96–108; (4) paravertebrals 110–128; (5) scales around midbody 99–117; (6) supraoculars 5–7; (7) internasals 4–5; (8) postrostrals 5–6; (9) loreals 3–7; (10) gulars 48–59; (11) lamellae on Finger IV 26–31; (12) lamellae on Toe IV 30–36; (13) posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; (14) postfemoral mite pocket distinct with slit-like opening [Type 2 of Torres-Carvajal (2007b)]; (15) parietal eye absent; (16) occipital scales small, smooth, juxtaposed; (17) projecting angulate temporal absent; (18) row of enlarged supraoculars occupying most of supraocular region absent; (19) scales on frontonasal region juxtaposed and smooth, not imbricate; (20) preauricular fringe short; (21) antegular, antehumeral, gular, longitudinal, oblique, postauricular, and supra-auricular neck folds present; (22) lateral nuchals and dorsals similar in size; (23) lateral body scales smaller than dorsals; (24) vertebrals enlarged, forming a distinct row of scales from forelimbs to hindlimbs; (25) dorsolateral crest absent; (26) paravertebrals and adjacent scales from midbody, smooth or feebly keeled, becoming keeled on the second half of body and mucronate between hindlimbs; (27) ventral scales smooth, imbricate; (28) scales on posterior surface of thighs granular; (29) prefemoral fold present; (30) inguinal fold present; (31) preanals not projected; (32) tail not compressed laterally; (33) tail relatively short (tail length 50–55% of total length); (34) caudal whorls per autotomic segment two; (35) tail spinose; (36) postocular stripe present; (37) dark patch on gular region in males absent; (38) dark patch on gular region in females absent; (39) black patch on ventral surface of neck in adult males absent; (40) dark midventral stripe in adult males absent; (41) dark patch on ventral surface of thighs, vent and tail in adult males absent; (42) background color of dorsum green, dark brown or olive green in both sexes; (43) postxiphisternal inscriptional ribs not examined. Description of holotype. Male (Fig. 6); SVL 57 mm; TL 114 mm; maximum head width 12.3 mm; head length 16.3 mm; head height 10.1 mm; scales on parietal and occipital regions small, smooth, juxtaposed, subequal in size; parietal eye not visible: supraoculars six, smooth, juxtaposed; circumorbitals absent; canthals two; loreals one; postrostrals four; internasals four; supralabials five; infralabials five; lorilabials in one row; preocular divided into two scales, most dorsal in contact with posterior canthal; lateral temporals granular; gulars in 55 rows between tympanic openings; all gulars cycloid, smooth, imbricate; second infralabial in contact with first, second and third sublabials; first pair of postmentals in contact; mental not separated from the infralabials by the first pair of postmentals; dorsal and lateral scales of neck and body granular; scales around midbody 107; vertebrals 104 moderately enlarged, keeled, imbricate, forming distinct vertebral row; paravertebrals and adjacent scales slightly smaller than vertebrals, smooth, subimbricate, becoming feebly keeled from the posterior half of dorsum and strongly keeled near hindlimbs insertion; paravertebrals 127; scales on flanks granulars; ventrals smooth, imbricate, more than twice the size of dorsals, only paravertebrals on the second half of body, nearly equal in size or slightly longer than ventrals; preauricular fringe short composed of three enlarged scales with round edge; suprauricular, antehumeral, gular, longitudinal, oblique, antegular, postauricular and rictal neck folds present; dorsolateral, ventrolateral and prefemoral folds present; dorsal scales of forelimbs imbricate, keeled; dorsal scales of hindlimbs imbricate, strongly keeled and mucronate; ventral humeral scales granular; ventral scales of fore- and hindlimbs smooth, imbricate; palmar scales imbricate, keeled and minutely mucronate; plantar scales imbricate, smooth or strongly keeled and mucronate; lamellae on Finger IV 28; lamellae on Toe IV 35; tail rounded (tail length 50% of total length); caudal scales strongly keeled, mucronate, imbricate; basal subcaudal scales smooth, imbricate; posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; postfemoral mite pocket distinct with slit-like opening [Type 2 of Torres-Carvajal (2007b)]. Color in life (Fig. 7 A-C): head and neck brownish gray with white flecks on head and white dots on neck; labials white with dark brown bars; postocular stripes dark brown, extending through the temporal and edge of occipital region to a black rhomboid blotch in the nuchal region; antehumeral collar black, distinct; dorsal surface of body green covered by bright green dots; forelimbs green with scattered bright green dots; hindlimbs brown with scattered white flecks and dots on posterior surface of thighs; tail black with scattered turquoise flecks on the basal half. Ventrally, gular region grayish white with white dots and black flecks; neck gray with few scattered black flecks; chest and belly cream with an orange hue on the posterior half; thighs, cloacal region, and tail dull orange. Iris dark brown. Color in ethanol 70% (Fig. 6 D-E): the dorsal surface turns dark brownish gray; postocular stripes and the nuchal blotch remain black; the white dots on the neck and the scattered white flecks on hindlimbs are dirty white; the bright green dots on the body and forelimbs are pale gray; tail turns dark brown. Ventrally, the gular region and neck is pale gray with dirty white dots and scattered black flecks, and chest, belly, limbs and base of tail are grayish white; the two distal thirds of the tail are dark brown with grayish white bars. Intraspecific variation. Measurements and scutellation of Stenocercus nigrocaudatus are presented in Table 1. Supralabials 4–5; infralabials 5–6; no specimens showed the second infralabials in contact with third sublabial; first pair of postmentals in contact medially in eight specimens (88.8%). Females larger than males (see Table 1), and both sexes are able to change color from green to dark brown or grayish brown. Sexual dimorphism in coloration is evident in the tail, which is black with scattered turquoise speckles in males (Fig. 7C) and brown with black and gray speckles in the proximal half and dark brown with gray rings in the distal half in females (Fig. 7J). The antehumeral collar is bold black in males and faint black or dark gray in females. Ventrally, the gular region in females is gray with scattered black flecks and speckles, the chest has a greenish hue, the belly is grayish white, and the ventral surface of hindlimbs, cloacal region and tail are tannish cream (Fig. 7I). The single female juvenile specimen (CORBIDI 19766) is dorsally identical to the adult female, but the gular region and chest possess a green hue. Distribution and natural history. Stenocercus nigrocaudatus is known from both sides of the inter-Andean valley of the Chinchipe River in the Cajamarca Department of northeastern Peru, between elevations of 1,700 and 1,892 m (Fig. 3). The two known localities of this species lie at the Yungas (500–2,300 m) ecoregion according to Brack-Egg (1986) and Peñaherrera del Águila (1989), and Eastern Cordillera Real montane forest following Olson et al. (2001). The general landscape in Alto Ihuamaca is composed of humid montane forest covering the steepest slopes and open areas with croplands for corn (Zea mays), coffee (Coffea sp.), and pastures for cattle ranching. In San José de Lourdes, the general landscape includes pastures for cattle ranching and small croplands for coffee, mango (Mangifera indica), and oranges (Citrus sp.), with some scattered patches of secondary forest and fringes of forest bordering ravines and along streams. Several individuals of S. nigrocaudatus were observed basking during sunny days between 900 and 1,500 hours. In small villages and single houses in the field, we observed individuals of S. nigrocaudatus basking on the walls at heights between 2 and 3 m (Fig. 7L), and one individual was observed at 7 m in the wall of a small building. This species also was common in open areas for cattle ranching basking on big tree trunks between 1 and 8 m above ground (Fig. 7K). Up to five individuals, a pair of adults and three juveniles, were observed in the same tree. All individuals observed basking showed a green dorsal coloration that changed to brownish gray to the moment of be captured. Sympatric squamate reptiles collected with S. nigrocaudatus were Alopoglossus buckleyi, Atractus gigas, Enyalioides anisolepis, and Potamites strangulatus; and in San José de Lourdes only Varzea altamazonica. Etymology. The specific epithet nigrocaudatus is a noun in apposition that derives from the Latin word “ nigrum ” that means black and “cauda” that means tail, with the suffix “ tus ” that means provided with. It refers to the black tail that is characteristic of the adult males of this new species.

Stenocercus asenlignus sp. nov. Figures 1–2 & 10 Holotype. CORBIDI 20219, an adult male, from Omia (6°28’12.702”S, 77°23’45.187”W, 1,381 m), Rodríguez de Mendoza Province, Amazonas Department, Peru, collected by P.J. Venegas and L.A. García-Ayachi on 5 December 2018. Paratypes (24): PERU: SAN MARTÍN DEPARTMENT: Mariscal Cáceres Province: MUSM 23034, adult male, MUSM 23035–38, adult females, and MUSM 23039, a juvenile, from El Dorado (06°46’00”S, 77°32’42”W, 1,600 m), collected by P.J. Venegas between 6 and 8 December 2003; CORBIDI 00622 adult female from Los Chilchos (06°42’28.7”S, 77°34’0.9”W, 1,800 m), collected by P.J. Venegas on 28 January 2008; CORBIDI 14780, adult male from Río Lejía (06° 50’11.6”S, 77°29’09.7”W, 1,500 m), collected by M. Salas on 14 June 2012; AMAZONAS DEPARTMENT: Rodríguez de Mendoza Province: CORBIDI 15658, juvenile, from Omia village (6°27’58.5”S, 77°23’50.9”W, 1,390 m), collected by A. García-Bravo on 11 November 2014; CORBIDI 20215–16, 20218, and 20221, adult males, CORBIDI 20214, 20217, and 20220, adult females, and CORBIDI 20222, a juvenile male, from Omia (6°28’12.702”S, 77°23’45.187”W, 1,381 m), collected by P.J. Venegas and L.A. García-Ayachi on 5 December 2018; CORBIDI 20135, adult female, from Santo Toribio village (6°1’55.179”S, 77°19’45.308”W, 1,622 m), collected by P.J. Venegas and A. García-Ayachi on 11 November 2018; CORBIDI 20198, juvenile female, CORBIDI 20199, juvenile male, and CORBIDI 20200–01, adult females, from Fundo Playas del Inca, Santo Toribio, Vista Alegre (6°1’56.356”S, 77°21’6.385”W, 1,682 m), collected by P.J. Venegas and L.A. García-Ayachi on 17 November 2018; CORBIDI 23003, a juvenile, from Limabamba (6°37’53.98”S, 77°26’22.33”W, 2,036 m), collected by Ivan Wong on 30 July 2019; HUÁNUCO DEPARTMENT: Marañón Province: CORBIDI 19549, adult female, from Nuevo Cajhán village, Cholón (8°52’8.076”S, 76°28’44.688”W, 1,625 m), collected by L.A. García-Ayachi on 23 June 2017. Diagnosis. From the 76 previously known species Stenocercus and the new species described herein, only S. arndti, S. leybachi sp. nov., S. bolivarensis Castro & Ayala, 1982, S. carrioni Parker, 1934, S. chlorostictus Cadle, 1991, S. crassicaudatus, S. empetrus, S. eunetopsis, S. flagracanthus, S. nigrocaudatus sp. nov., S. qalaywasi sp. nov., S. torquatus and S. simonsii Boulenger, 1901, share with S. asenlignus granular scales on posterior surface of thighs, relatively short tail, caudals spinose, and two caudal whorls per autotomic segment. However, S. torquatus and S. qalaywasi, are easily distinguished from S. asenlignus (state of character between parentheses) by having transverse black nuchal bands (absent), a middorsally complete antehumeral black collar (incomplete) and, only in the case of S. torquatus (Fig. 10A), the dorsum is emerald green without bands (green with black bands in males). Moreover, S. qalaywasi possesses a longer tail with 57–60 % of the total length versus 49–57% in S. asenlignus. Live male individuals of S. nigrocaudatus can be readily distinguished from S. asenlignus by having the tail black with scattered turquoise spots (tail light brown or grayish brown with dark gray spots or bands) and the body without dorsal black bands (present). In addition, in S. asenlignus the dorsal scales of the body are keeled, becoming gradually strongly keeled and mucronate toward the hindlimb insertion and in S. nigrocaudatus dorsal scales are smooth and feebly keeled becoming strongly keeled but not mucronate close to the hindlimbs insertion. Stenocercus leybachi can be readily distinguished from S. asenlignus by having a distinct, low, serrate crest on the neck that can reach or not to the middle of dorsum, while in S. asenlignus, vertebrals form an indistinct row of enlarged scales along the body. Moreover, S. asenlignus has more vertebrals than S. leybachi (71–106, = 89.8 versus 63–73, = 68.6, respectively). Stenocercus torquatus has more scales around midbody than S. asenlignus (102 to 137, = 116.9 versus 78 to 111, = 96.4, respectively). The recently described S. flagracanthus differs from S. asenlignus in having a tail strongly armed with projected mucronate scales that are less developed in S. asenlignus. In the distal half of the tail of S. flagracanthus the spines are conspicuously alternating in size, with large spines followed by small spines per each caudal whorl, and in S. asenlignus, the alternation in size of spines is undistinguishable. Dorsal scales between the posterior half of body and hindlimbs insertion become enlarged and strongly keeled with strongly projected mucronate scales in S. flagracanthus, while in S. asenlignus, they are keeled and, in some specimens, slightly mucronate. Furthermore, the dorsal and gular pattern is different in both species (state of characters in S. flagracanthus between parentheses): usually adult males of S. asenlignus possess a “zig-zag” pattern of black dorsal bars on dorsum (bold black bars; see Fig. 11 in Venegas et al. 2020a), antehumeral collar bordered by cream spots (cream line), and preserved specimens have the gular region gray with scattered black flecks (gray with cream dots). The other species such as S. carrioni, S. chlorostictus and S. eunetopsis differ from S. anselignus by having dorsal scales of neck keeled and imbricate (granular in S. asenlignus). Stenocercus eunetopsis has a considerably longer tail than S. asenlignus (64–66% of total length vs. 49–57%, respectively), and S. chlorostictus has a strong sexual dichromatism, with the dorsal background color bright green in males and brown in females (males and females gray, brown or green in S. asenlignus). Stenocercus bolivarensis differs from S. asenlignus by having strongly keeled and imbricate lateral body scales (Torres-Carvajal 2007b), which are granular or smooth in S. asenlignus. Stenocercus asenlignus differs from S. crassicaudatus by having fewer paravertebrals (92 to 118, = 105.8 versus 107 to 166, = 126.6), and a shorter tail (49 to 57% of total length versus 57 to 62%). Males of S. arndti are easily distinguished from S. asenlignus by having a bold black transverse band at midbody that extends ventrolaterally (absent in S. asenlignus) and dorsal scales of neck slightly keeled and subimbricate (granular in S. asenlignus). Stenocercus simonsii differs from S. asenlignus (character states in parentheses) by having dorsals imbricate, moderately keeled, but not mucronate (dorsals granular in the anterior half of body, getting gradually enlarged and keeled from the posterior half of body to strongly keeled and mucronate near to the hindlimbs insertion). Stenocercus empetrus differs from S. asenlignus by having the venter yellowish-orange with black reticulations, or completely black, whereas in the new species the venter is gray without reticulations. In addition, S. simonsii and S. empetrus are larger than S. asenlignus (maximum SVL = 88 mm in males and 79 mm in females of S. simonsii, SVL = 103 mm in males and 90 mm in females of S. empetrus, and maximum SVL = 73 mm in males and 70 mm in females of S. asenlignus). Characterization. (1) Maximum SVL in males 73 mm (n = 9); (2) maximum SVL in females 70 mm (n = 14); (3) vertebrals 71–106; (4) paravertebrals 92–118; (5) scales around midbody 78–111; (6) supraoculars 5–8; (7) internasals 4–5; (8) postrostrals 4–6; (9) loreals 2–6; (10) gulars 47–60; (11) lamellae on Finger IV 23–30; (12) lamellae on Toe IV 28–34; (13) posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; (14) postfemoral mite pocket distinct with slit-like opening [Type 2 of Torres-Carvajal (2007b)]; (15) parietal eye absent; (16) occipital scales small, smooth, juxtaposed; (17) projecting angulate temporal absent; (18) row of enlarged supraoculars occupying most of supraocular region absent; (19) scales on frontonasal region juxtaposed, smooth, not imbricate; (20) preauricular fringe short; (21) antehumeral, gular, longitudinal, oblique, postauricular, supra-auricular, antegular neck folds present; (22) lateral nuchals and dorsals similar in size; (23) lateral body scales smaller than dorsals; (24) vertebrals slightly enlarged, forming a distinct row of scales from forelimbs to hindlimbs; (25) dorsolateral crest absent; (26) paravertebrals and adjacent scales from midbody keeled, becoming strongly keeled and mucronate at the posterior half of body; (27) ventral scales smooth, imbricate; (28) scales on posterior surface of thighs granular; (29) prefemoral fold present; (30) inguinal fold present, weakly defined; (31) preanals not projected; (32) tail not compressed laterally; (33) tail relatively short (tail length 49–57% of total length); (34) caudal whorls per autotomic segment two; (35) tail spinose; (36) postocular stripe absent or present; (37) gular region in males dark gray with black dots; (38) gular region in females grayish yellow with light green dots; (39) black patch on ventral surface of neck in adult males absent; (40) dark midventral stripe in adult males absent; (41) dark patch on ventral surface of thighs, vent and tail in adult males absent; (42) background color of dorsum green, brown or grayish in both males and females, with a “zig-zag” pattern of black transversal bands in adult males; (43) two long postxiphisternal pairs of inscriptional ribs not in contact midventrally (pattern 4A of Torres-Carvajal, 2004). Description of holotype. Male (Fig. 1); SVL 69 mm; TL 88 mm; maximum head width 14.61 mm; head length 17.93 mm; head height 11.20 mm; scales on parietal and occipital regions small, smooth, juxtaposed, subequal in size; parietal eye not visible: supraoculars seven, smooth, juxtaposed; circumorbitals absent; canthals two; loreals three; postrostrals four; internasals four; supralabials five; infralabials five; lorilabials in one row; preocular divided into three scales, most dorsal in contact with posterior canthal; lateral temporals granular; gulars in 57 rows between tympanic openings; all gulars cycloid, smooth, imbricate; second infralabial in contact with first, second and third sublabials; first pair of postmentals in contact; mental not separated from the infralabials by the first pair of postmentals; dorsal and lateral scales of neck and body granular; scales around midbody 97; vertebrals 90 enlarged, keeled, imbricate, forming distinct vertebral row; paravertebrals and adjacent scales slightly smaller than vertebral row, keeled, imbricate, becoming mucronate from midbody to hindlimb insertion; paravertebrals 100; ventrals smooth, imbricate, more than twice the size of dorsals, except for paravertebrals at the second half of body, which are nearly equal in size or slightly longer than ventrals; preauricular fringe short, composed of four enlarged, granular scales; suprauricular, antehumeral, gular, longitudinal, oblique, antegular, postauricular and rictal neck folds present; dorsolateral, ventrolateral and prefemoral folds present; dorsal scales of forelimbs imbricate, keeled; dorsal scales of hindlimbs imbricate, strongly keeled and mucronate; ventral humeral scales granular; ventral scales of fore and hindlimbs smooth, imbricate; palmar scales imbricate, keeled; plantar scales imbricate, strongly keeled, mucronate; lamellae on Finger IV 23; lamellae on Toe IV 29; tail rounded (tail length 55% of total length); caudal scales strongly keeled, mucronate, imbricate; basal subcaudal scales smooth, imbricate; posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; postfemoral mite pocket distinct with slit-like opening [Type 2 of Torres-Carvajal (2007b)]. Color in life of holotype: dorsally green (from head to the anterior half of body, including forelimbs) speckled with dark gray flecks and with transverse rows of light green dots; posterior half of body and hindlimbs pale brown with the same pattern of flecks and dots scattered of the green half but the light green dots are faint on hindlimbs; tail light brown with black speckles and black bands on the distal third; incomplete middorsal black collar at antehumeral fold and a dorsal “zig-zag” pattern of black bands on vertebral line. Ventrally, the gular region is dark gray with scattered black flecks, chest pale green and venter grayish white. Once captured, it quickly changes its dorsal color from green to brownish gray, with scattered black flecks and cream dots (Fig. 2A). Limbs change from green with black flecks to gray with scattered black flecks and pale cream dots. Distal portion of tail remains light brown with black bands. Iris dark brown. Color in preservative (Fig. 1 D-E): dorsal surface dark gray with scattered black and pale dots, dorsal “zig-zag” bands pattern remains evident. Gular region dark gray with black dots and venter gray. Intraspecific variation. Measurements, scutellation, and other morphological characters of Stenocercus asenlignus are presented in Table 1. Supralabials 4–7; infralabials 4–7; second infralabials in contact with third sublabials in all specimens, except in MUSM 23035; first pair of postmentals in contact medially only in the specimen MUSM 23039. In two dissected specimens, the pattern was three xiphisternal and two long postxiphisternal pairs of inscriptional ribs not in contact midventrally (Pattern 4A; Torres-Carvajal 2004). Sexual dimorphism in size is slightly noticeable (Table 1). The head of adult males looks more robust than the females, and both sexes are able to change color from green to brownish gray or bluish gray in males (Fig. 2) and green to dark gray or pale brown in females. Black collar and “zig-zag” bands dorsal pattern are distinct only in males (Fig. 2A, C & L) and absent or faint in females (Fig. 2D, F & H) and juveniles (Fig. 2I). In adult females throat can be cream with gray flecks and the chest dirty cream (Fig. 2E) or throat grayish green with light green dots and chest green (Fig. 2G), and the venter is gray with a pink tone (Fig. 2E). Juveniles have the throat yellowish with light yellow flecks (Fig. 2J) or green with light green flecks, and the chest and ventral surface of forelimbs pale green. Some males possess transverse rows of yellow or light green dots on body surface and the throat and chest yellowish when basking (Figs. 2K & 10B). Distribution and natural history observations. Stenocercus asenlignus is known from five localities along the Amazon slope of the northern portion of the Central Andes, along the Huallabamba River basin in the departments of Amazonas and San Martín, at elevations between 1500 and 2036 m (Fig. 3). According to Olson et al. (2001), the distribution of S. asenlignus lies inside the Peruvian Yungas ecoregion. At the localities of El Dorado and Río Lejía the habitat is characterized by dense primary forests with some coffee and yuca plots. In Los Chilchos the habitat was secondary forest with open areas for pasture. The general landscape in Playa Los Incas was open areas for cattle ranching near the rivers and slopes covered by primary montane forest. Omia is a small village surrounded by crops of coffee (Coffea sp.), cacao (Theobroma cacao) and mango (Mangifera indica). Most specimens were found on tree trunks inside the forest or at the edge of crop areas, between 2 and 3 m above ground; however, several uncollected individuals were observed at heights between 5 and 10 m. A couple of adult individuals were observed on the rocky slope of a cliff at 5 m height. One adult male (MUSM 23034) was collected on a wall of a “tambo,” a rural house made of logs. When disturbed it hid in a carpenter bee hole. Hatchlings and juveniles were observed basking on tambo walls and fallen trees around crops and near the base of large trees. In Omia village Stenocercus asenlignus is a common species and several individuals were observed basking on house walls and using the holes and crevices between bricks as retreats (Fig. 2L). Individuals observed basking on trees and house walls were found with green dorsum and at the moment of capture this changed abruptly to dark gray or brownish gray color. However, individuals observed on trees and rock walls in the shadow were also found with a grayish brown dorsum. Female CORBIDI 0622 (SVL = 61) collected in the rainy season (January 2008) had 2 and 4 follicles, in the left and right ovary, respectively. Female MUSM 23038 (SVL = 62 mm) had two underdeveloped eggs (pale yellow) that were 9.6–10.3 mm long, 8– 7.8 mm wide, and 156.82–172.57 mm 3 in volume. Female MUSM 23036 (SVL = 70 mm) had two fully developed eggs with white, hard shell (22–22.1 mm long, 8.5–8.6 mm wide and 393.42–396.25 mm 3 of volume); it was found digging a hole in a cavity between roots, this behavior suggests that it was building a nest to deposit the eggs. Also, the presence of hatchlings and juveniles around buttress roots suggests that S. asenlignus deposits their eggs between them. Both gravid females (MUSM 23036, 23038) and a juvenile (MUSM 23039, SVL = 37) were collected at the beginning of the rainy season (December, 2003). Stenocercus asenlignus is not sympatric with other Stenocercus or Tropiduridae species. The only known lizard species sympatric with S. asenlignus are Alopoglossus buckleyi, Anolis fuscoauratus, Cercosaura doanae, and Enyalioides sophiarothschildae. Etymology. The specific epithet asenlignus is a noun in apposition and derives from the Latin words “ asen ” (= climb or ascend) and “ lignus ” (= trunk). It refers to the arboreal habitus of the new species. Remarks. Stenocercus crassicaudatus was reported by Fritts (1974) for San Martín and Loreto departments, based on a neonate (AMNH 57176) and a subadult male (AMNH 57173), respectively, that were examined later by Torres-Carvajal et al. (2005). According to Torres-Carvajal et al. (2005), both specimens are more similar morphologically to S. torquatus; they concluded that S. crassicaudatus is restricted to Cusco Department. While in the absence of a major sample from Loreto and San Martín, they also concluded that S. torquatus is restricted to the Chanchamayo Valley and adjacent areas in Junín and Pasco departments in Central Peru (Torres-Carvajal et al. 2005). Although we did not review the specimens reported by Fritts (1974), we cons

Stenocercus qalaywasi sp. nov. Figures 8–9 Holotype. CORBIDI 20567, adult male from Lampa Pariahuanca, Pariahuanca district, Huancayo province, Junín Department, Peru (11°58’51.9”S, 74°53’47.6”O, 2,587 m), collected by Luis A. García-Ayachi on 19 June 2019. Paratype. CORBIDI 20568, an adult female collected with the holotype. Diagnosis. From all currently known species of Stenocercus (including the new species described herein), S. qalaywasi sp. nov. is only similar to thirteen species (e.g., S. asenlignus sp. nov., S. arndti, S. flagracanthus, S. leybachi sp. nov., S. bolivarensis, S. carrioni, S. chlorostictus, S. crassicaudatus, S. empetrus, S. eunetopsis, S. nigrocaudatus sp. nov., S. torquatus and S. simonsii) in sharing the following characters: granular scales on posterior surface of thighs, relatively short tail, caudals spinose, and two caudal whorls per autotomic segment. From these species, S. qalaywasi possesses a smaller number of vertebrals than S. nigrocaudatus and S. torquatus (77–79 in S. qalaywasi versus 96–108 in S. nigrocaudatus and 83–115 in S. torquatus), scales on dorsal surface of neck keeled (granular in S. asenlignus, S. nigrocaudatus and S. torquatus), a longer tail than S. asenlignus, S. nigrocaudatus and S. torquatus (tail length 57–60% of total length in S. qalaywasi, 51–55% in S. asenlignus, 50–55% in S. nigrocaudatus, and 47–54% in S. torquatus). Stenocercus leybachi is easily distinguished from S. qalaywasi by having a distinct, serrate, low crest on neck (absent in S. qalaywasi) and by lacking a distinct, black antehumeral collar (complete middorsally in S. qalaywasi). Stenocercus arndti, S. crassicaudatus, S. empetrus, S. flagracanthus, and S. simonsii can also be easily distinguished from S. qalaywasi by having the scales on dorsal surface of neck granular, while in the new species they are keeled. Furthermore, S. crassicaudatus and S. flagracanthus possess more vertebrals (83–97) than S. qalaywasi (77–79). In the case of S. flagracanthus, the tail is shorter (50–54% of total length) than S. qalaywasi (57–60%). Species such as S. bolivarensis, S. carrioni, S. chlorostictus, and S. eunetopsis possess keeled scales on the dorsal surface of neck, like S. qalaywasi, and preserved specimens can be confused. However, these species can be distinguished by the following features: from S. arndti, S. carrioni, S. chlorostictus, S. empetrus, and S. simonsii by having a distinct black, middorsally complete, antehumeral collar and two nuchal bands (antehumeral collar incomplete middorsally and nuchal bands absent in the aforementioned species); from S. carrioni and S. chlorostictus by having more vertebral scales (55–72 in S. carrioni, 63–73 in S. chlorostictus and 77–79 in S. qalaywasi); from S. bolivarensis by having the lateral scales of body granular (strongly keeled in S. bolivarensis); and from S. eunetopsis by having more scales around midbody (60–80 in S. eunetopsis and 87–92 in S. qalaywasi) and a shorter tail (57–60% of total length vs. 62–66% in S. eunetopsis). Characterization. (1) Maximum SVL in males 88 mm (n = 1); (2) maximum SVL in females 95 mm (n = 1); (3) vertebrals 77–79; (4) paravertebrals 104–108; (5) scales around midbody 87–92; (6) supraoculars six; (7) internasals four; (8) postrostrals six; (9) loreals five; (10) gulars 44; (11) subdigitals on Finger IV 26–29; (12) subdigitals on Toe IV 33–34; (13) posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; (14) postfemoral mite pocket distinct with slit-like opening [Type 2 of Torres-Carvajal (2007b)]; (15) parietal eye not visible; (16) scales on occipitoparietal region small, rugose, juxtaposed; (17) projecting angulate temporal absent; (18) row of enlarged supraoculars occupying most of supraocular region absent; (19) scales on frontonasal region juxtaposed, rugose; (20) preauricular fringe present; (21) antegular, antehumeral, gular, longitudinal, and postauricular neck folds present; (22) lateral and dorsal nuchals similar in size; (23) posterior gulars cycloid, smooth, slightly imbricate, not notched; (24) lateral body scales smaller than dorsals, reduced in size, approximately one third of the size of dorsal body scales closer to vertebral line; (25) vertebrals larger than adjacent paravertebrals forming a distinct vertebral row; (26) dorsolateral crest absent; (27) ventrals smooth, imbricate; (28) scales on posterior surface of thighs granular; (29) prefemoral fold present; (30) inguinal groove present; (31) preanals not projected; (32) tail not compressed laterally in adult males; (33) tail relatively short (tail length 57–60% of total length); (34) two caudal whorls per autotomic segment; (35) caudals spinose; (36) dark stripe extending anterodorsally from subocular region to supraciliaries absent; (37) dark patch extensively covering gular region of females absent; (38) dark patch extensively covering gular region of adult males absent; (39) black patch on ventral surface of neck in adult males absent; (40) dark midventral longitudinal mark, such as faint line, conspicuous stripe, or extensive patch in adult males absent; (41) black patches on ventral surfaces of thighs in adult males absent; (42) background color of dorsum green or dark gray, with distinct black bands in adults individuals of both sexes; (43) postxiphisternal inscriptional ribs not examined. Description of the holotype. Male (Fig. 8); SVL 88 mm; TL 136 mm; maximum head width 16.8 mm; head length 21.4 mm; head height 13.2 mm; posterior dorsal head scales small, smooth, juxtaposed; parietal eye not visible; supraoculars in six rows, smooth, juxtaposed, with the most lateral two rows less than half the size of the medial adjacent rows; distinct circumorbitals absent; canthals two; internasals four; postrostrals five, two lateral ones larger; supralabials six; infralabials six; loreals four; lorilabials in one row; preoculars two, the dorsal-most in contact with posterior canthal; lateral temporals granular; gulars in 44 rows between tympanic openings; all gulars cycloid, smooth, imbricate, not notched; second infralabial in contact with first two sublabials; first pair of postmentals partially in contact medially; mental in contact with first pair of infralabials but not with the first pair of postmentals; dorsal scales of neck small, weakly keeled, slightly imbricate, and slightly larger than granular laterals; dorsal scales of body imbricate, keeled, becoming smaller, slightly keeled or smooth towards flanks; scales around midbody 87; vertebrals 77, enlarged, keeled, imbricate, forming a distinct vertebral row; paravertebrals adjacent to vertebral row 104, same size or slightly smaller than vertebrals; ventrals smooth, imbricate, larger than dorsals; preauricular fringe short, composed by two enlarged, projected scales; antegular, antehumeral, gular, longitudinal, and postauricular neck folds present; ventrolateral fold present; humeral dorsal scales imbricate, weakly keeled; dorsal scales of forelimbs imbricate, keeled; dorsal scales of hindlimbs imbricate, keeled, mucronate; ventral humeral scales imbricate; ventral scales of forearms keeled, imbricate, and ventral scales of hindlimbs imbricate, smooth; palmars imbricate, keeled; plantars imbricate, keeled, mucronate; lamellae on Finger IV 26; lamellae on Toe IV 33; tail rounded; caudals strongly keeled, mucronate, imbricate dorsally; two caudal whorls per autotomic segment; basal subcaudals strongly keeled, imbricate; posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; postfemoral mite pocket distinct with slit-like opening; [Type 2 of Torres-Carvajal (2007b)]. Color in life of holotype (Fig. 9 A-C): Head bright green with a narrow gray postocular stripe and two gray stripes below it; dorsal surface of neck with two pale gray transverse bands and a distinct, middorsally complete black antehumeral collar; dorsum, limbs and tail with a green hue and scattered dark gray flecks; dorsum and forelimbs also covered by bright green specks; gular region dark gray, spotted with light gray blotches, and bearing a pale gray medial patch posteriorly; ventral surface of neck pale gray; chest greenish gray; belly light pink; ventral surface of hips and hindlimbs cream; cloacal region and ventral surface of base of tail cream with a light pink hue; ventral surface of tail gray becoming dark gray towards tip. Iris brown. Color in preservative (Fig. 8): dorsal surface dark gray; the postorbital gray stripe black; bands on neck and antehumeral collar black; dorsum with short irregular black bands along the vertebral region and covered with light gray specks; forelimbs covered with light gray specks and hindlimbs with darker bands than the gray background; fingers and toes light gray with black spots. Ventral surface similar as in life, but without the pink and green hues. Intraspecific variation. Scale counts and measurements for Stenocercus qalaywasi are presented in Table 1. Loreals 4–5; postrostrals 4–5; second infralabial not in contact with third sublabial in all specimens; first pair of postmentals in contact in both specimens. Sexual dimorphism is not evident in S. qalaywasi; the single female paratype (CORBIDI 20568) differs from the male holotype only in having the antehumeral black collar incomplete (Fig. 9E). Ventrally, the gular coloration is greenish cream with cream spots laterally in the female paratype (Fig. 9F), and dark gray with light gray spots in the male holotype. With a low sample of two specimens, the female is larger (95 mm) than the male (88 mm SVL). Distribution and natural history. Stenocercus qalaywasi is known only from the village of Lampa Pariahuanca in the inter-Andean valley of the Mantaro River in central Peru (Fig. 3). It occurs at an elevation of 2,587 m in the department of Junín. The type locality lies within the Peruvian Yungas ecoregion following Olson et al. (2001) and Yungas ecoregion according to Brack-Egg (1986) and Peñaherrera del Águila (1989). Six individuals of S. qalaywasi were observed basking on sunny days at 0900 hours on the rooftops of Lampa Pariahuanca village houses. When disturbed, they hid under the roof tiles, in holes between bricks or in the slit between roof and wall. The surrounded areas of the village are croplands of corn (Zea mays), potato (Solanum tuberosum), carrot (Daucus carota), and barley (Hordeum vulgare), with a few scattered patches of secondary montane forest on the steepest slopes. No other species of lizards or snakes were recorded at this locality. When the adult individuals of S. qalaywasi are basking, they possess the head bright green and the dorsal surface of body and tail with a green hue bearing conspicuous light green specks on back (Fig 9G). At the moment of capture the single male collected changed dramatically in coloration to dark gray with the dorsum containing light gray specks (Fig. 9A). The single collected female specimen did not show a dramatic change of coloration becoming simply dull green (Fig. 9D). Etymology. The specific epithet “ qalaywasi ” is a noun in apposition derived from two words in Quechua, “ qalaywa ” that means lizard and “ wasi ” that means home or house. The specific name refers to the habitus of this species of living in the houses of Lampa Pariahuanca village.

Stenocercus leybachi sp. nov. Figures 4–5 Holotype. CORBIDI 16397, an adult male, from Comunidad Saria, Chaglla (9°43’27.7”S, 75°48’35.9”W, 1,082 m), Huánuco Province, Huánuco Department, Peru, collected by D. Vásquez on 11 October 2015. Paratypes (22). PERU: HUÁNUCO DEPARTMENT: Huánuco Province: CORBIDI 9323, adult female, from Chinchavito (9° 33’ 27.2”S, 75° 55’ 07.1”W, 824 m), collected by P.J. Venegas on 16 June 2011; CORBIDI 13659, juvenile male, from Miraflores (9°41’0.11”S, 75°50’33.44”W, 1,270 m), collected by V. Duran and L. Lujan on 11 October 2013; CORBIDI 16390, a juvenile, CORBIDI 16394–95 and 16398, males, CORBIDI 16399–16400, females, from Saria, Chaglla (9°42’55.4”S, 75°49’3”W, 1,151 m), collected by D. Vásquez on 24 August 2015 and 10 October 2015; CORBIDI 16412 juvenile, CORBIDI 16428–29, 16431, females, CORBIDI 16432, juvenile, CORBIDI 16437, female, from Agua Nueva, Chinchao (9°41’59.82”S, 75°49’55.39”W, 1,115 m), collected by J. C. Chávez-Arribasplata within 24 to 28 September 2015 and 1 to 4 October 2015; CORBIDI 16525–26, a juvenile and female, CORBIDI 16532–33, male and juvenile, CORBIDI 16539, female, and CORBIDI 16594, juvenile, also from Agua Nueva, Chinchao (9°43’6.67”S, 75°48’56.1”W, 1,185 m), collected by A.C. Barboza within 10 to 15 November 2015; Pachitea Province: CORBIDI 13333, male, from Casa de Máquinas, Chaglla (9°42’17.81”S, 75°49’47.96”W, 928 m), collected by V. Duran and L. Luján on August 2013; CORBIDI 13334, male, from El Waro, Chaglla (9°41’55.87”S, 75°49’46.56”W, 927 m), collected by V. Duran and L. Luján on August 2013. Diagnosis. Stenocercus leybachi differs from all other Stenocercus species, except S. arndti, S. asenlignus sp. nov., S. bolivarensis, S. carrioni, S. chlorostictus, S. crassicaudatus, S. empetrus, S. eunetopsis, S. flagracanthus, S. nigrocaudatus sp. nov., S. qalaywasi sp. nov., S. torquatus, and S. simonsii, by having granular scales on posterior surface of thighs, relatively short tail, caudals spinose and two caudal whorls per autotomic segment. Nevertheless, S. leybachi can be easily distinguished from all aforementioned species by having a distinct serrate low crest on neck, that in some specimens reach to the middle of the dorsum. We found the arboreal S. chinchaoensis, a species known from the Upper Huallaga Basin at Huánuco Department (Venegas et al. 2013), sympatric with S. leybachi in the locality of Agua Nueva, Chinchao district, at elevations of 1,115 to 1,200 m. This species also has the ability to change color between green and gray, however this has a longer tail (tail length 61–64% of total length versus 52–58% of total length, respectively) and caudal scales not spinose. Stenocercus boettgeri is another green species distributed in the Amazon slope of central Peru from Huánuco, Pasco and Junín departments, at elevations between 2900 and 3250 m (Torres-Carvajal 2007b). Although this species can be confused with S. leybachi, the former species can be readily distinguished by having the lateral neck scales less than half the size of dorsal neck scales (dorsal and lateral neck scales similar in size in S. leybachi) and lacking a spinose tail. Characterization. (1) Maximum SVL in males 84mm (n=6); (2) maximum SVL in females 82mm (n=7); (3) vertebrals 63–73; (4) paravertebrals 100–112; (5) scales around midbody 74–97; (6) supraoculars 7–9; (7) internasals 4; (8) postrostrals 4–6; (9) loreals 3–5; (10) gulars 42–61; (11) subdigitals on Finger IV 21–28; (12) subdigitals on Toe IV 28–32; (13) posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; (14) postfemoral mite pocket distinct with slit-like opening [Type 2 of Torres-Carvajal (2007b)]; (15) parietal eye not visible; (16) scales on occipitoparietal region small, some rugose and other smooth, juxtaposed; (17) projecting angulate temporal absent; (18) row of enlarged supraoculars occupying most of supraocular region absent; (19) scales on frontonasal region juxtaposed, smooth, slightly imbricate; (20) preauricular fringe present; (21) antegular, antehumeral, gular, longitudinal, and postauricular neck folds present; (22) lateral and dorsal nuchals similar in size; (23) posterior gulars cycloid, smooth, slightly imbricate, not notched; (24) lateral body scales smaller than dorsals, reduced in size, approximately one third of the size of dorsal body scales closer to vertebral line; (25) vertebrals larger than adjacent paravertebrals forming a conspicuous vertebral row and a distinct low serrate crest on neck that in some specimens comes to the middle of dorsum; (26) dorsolateral crest absent; (27) ventrals smooth, imbricate; (28) scales on posterior surface of thighs granular; (29) prefemoral fold present; (30) inguinal groove present; (31) preanals not projected; (32) tail not compressed laterally in adult males; (33) tail relatively short (tail length 52–58 % of total length); (34) two caudal whorls per autotomic segment; (35) caudals spinose; (36) dark stripe extending anterodorsally from subocular region to supraciliaries absent; (37) dark patch extensively covering gular region of females absent; (38) dark patch extensively covering gular region of adult males absent; (39) black patch on ventral surface of neck in adult males absent; (40) dark midventral longitudinal mark, such as faint line, conspicuous stripe, or extensive patch in adult males absent; (41) black patches on ventral surfaces of thighs in adult males absent; (42) background color of dorsum green, dark brown or gray and without distinct black bands in adult individuals of both sexes; (43) postxiphisternal inscriptional ribs not in contact midventrally [Pattern 4A of Torres-Carvajal 2004)]. Description of the holotype. Male (Fig. 4); SVL 83 mm; TL 117 mm; maximum head width 16.5 mm; head length 20.1 mm; head height 12.7 mm; posterior dorsal head scales small, smooth, slightly imbricate, juxtaposed; parietal eye not visible; supraoculars in seven rows, smooth, slightly imbricate, with the most lateral two rows less than half the size of the medial adjacent rows; distinct circumorbitals absent; canthals two; internasals four; postrostrals four, two median ones larger; supralabials six; infralabials five; loreals four; lorilabials in two rows; preoculars three, the middle one tiny, the dorsal-most in contact with posterior canthal; lateral temporals granular; gulars in 47 rows between tympanic openings; all gulars cycloid, smooth, slightly imbricate, not notched; second infralabial in contact with first three sublabials; first pair of postmentals not in contact medially; mental in contact with first pair of infralabials and first pair of postmentals; dorsal scales of neck keeled and lateral scales of neck granular; dorsal scales of body imbricate, keeled, feebly mucronate becoming smaller and slightly keeled to smooth towards flanks; scales around midbody 86; vertebrals enlarged, keeled, imbricate, in 73 rows, forming distinct vertebral row and a low serrate crest from the neck to the middle of dorsum; paravertebrals adjacent to vertebral row same size as dorsals, keeled, and imbricate; paravertebrals 107; ventrals smooth, imbricate, one third larger than dorsals; preauricular fringe short, composed of two enlarged, posteriorly projected scales; antegular, antehumeral, gular, longitudinal, and postauricular neck folds present; ventrolateral fold present; dorsal humeral scales imbricate, weakly keeled; scales of forearms imbricate, keeled; dorsal scales of hindlimbs imbricate, strongly keeled, mucronate; ventral humeral scales imbricate, weakly keeled; ventral scales of forearms and hindlimbs imbricate, smooth; palmars imbricate, weakly keeled; plantars imbricate, smooth; lamellae on Finger IV 24; lamellae on Toe IV 29; tail rounded (tail length 58% of total length); caudals strongly keeled, mucronate, imbricate dorsally; two caudal whorls per autotomic segment; basal subcaudals slightly keeled, imbricate; posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; postfemoral mite pocket distinct with slit-like opening; [Type 2 of Torres-Carvajal (2007b)]. Color in life of holotype (Fig. 5 A-C): dorsum emerald green with whitish and turquoise spots on head and neck, and pale greenish yellow spots on dorsum; pelvic region, hindlimbs and tail pale brown covered by dark gray reticulations and pale greenish yellow spots; throat brownish gray with pale gray spots; ventral surface including base of tail dirty cream and rest of tail darker than the base. Once captured it quickly changes its dorsal color from green to dark brown, sprinkled with dirty cream spots on head and neck, and yellowish cream spots on dorsum; forelimbs, hindlimbs and tail dark grayish brown, darker on tail and with a greenish tone on forelimbs; some dirty cream spots are present on hindlimbs. Iris pale brown. Color in preservative (Fig. 4 D-E): head, forelimbs and dorsum to pelvic region greenish gray, sprinkled with cream spots; anterior surface of thighs greenish gray and the rest of hindlimbs, pelvic region and tail grayish brown with scattered dark gray flecks and reticulations. The last one third of tail is black. The throat is greenish gray without spots, the rest of ventral surface of body grayish cream. Intraspecific variation. Measurements,scutellation, and other morphological characters of Stenocercus leybachi are presented in Table 1. Supralabials 4–6; infralabials 5–6; second infralabials not in contact with third sublabials in sixteen specimens (69.5%); first pair of postmentals in contact medially only in four specimens (17.3%). In two dissected specimens, the rib pattern was three xiphisternal and two long postxiphisternal pairs of inscriptional ribs not in contact midventrally, [Pattern 4A of Torres-Carvajal (2004)]. Females are smaller than males (Table 1) and both sexes are able to change color from green to dark brown or grayish brown (see Fig. 5). The seven adult males in the type series lack a black antehumeral collar and of the seven adult females, one (CORBIDI 16429) possesses a middorsally complete collar. Complete black antehumeral collar is present in eight of nine juveniles, only one specimen (CORBIDI 16431) has an incomplete black collar. Adult specimens of both sexes and juveniles possess pale spots on dorsum and some specimens also have scattered black flecks. The throat in adult females can be brownish green with pale green spots, chest with a greenish tone and the belly is dirty cream with or without a pinkish hue on the belly and base of tail. Juveniles have throat and venter yellowish green. Distribution and natural history. Stenocercus leybachi is known from five close localities in the Amazon foothills of the Río Huallaga basin, at elevations between 824–1,270 m, in central Peru (Fig. 3). The known localities of this species lie in the Huánuco Department within the Yungas (500–2,300 m) ecoregion according to Brack–Egg (1986) and Peñaherrera del Aguila (1989), and Peruvian Yungas following Olson et al. (2001). The general habitat where the new species was collected is composed of croplands of coca (Erythroxylum coca), coffee (Coffea sp.), cacao (Theobroma cacao), corn (Zea mays), orange (Citrus sp.) and pastures for cattle ranching with scattered patches of secondary montane forest, especially on the steepest slopes. Individuals of S. leybachi were observed active during sunny days basking on tree trunks at 1.5–6 m above ground. When these individuals felt disturbed, they climbed the tree trunk finding refuge up high. Some individuals were observed and collected with a fishing rod while basking on fallen trees. The individuals found basking were light green and at the moment of capture suddenly changed to brown or brownish gray. Most specimens were collected in the forest canopy, during a flood for the construction of a hydroelectric dam. The specimens were collected by hand on the branches of high trees (5 to 10 m) from a boat, and some individuals tried to escape by hiding in tree holes (Fig. 5 K-L) and cracks in the bark of the trees. Stenocercus leybachi was syntopic in the area of the flood with other arboreal lizards such as Anolis punctatus, Euspondylus excelsum, and S. chinchaoensis. Other sympatric species of squamate reptiles collected with S. leybachi were: A. ortonii, Bothrops chloromelas, Dipsas catesbyi, D. indica, D. schunkii, Drymoluber dichrous, Enyalioides feiruzae, Micrurus annelatus, Oxyrhopus leucomelas, Phrynonax polylepis, Proctoporus sp., and S. prionotus. Etymology. The specific name leybachi is a patronym for Achim Leybach of Marktsteft, Germany, in recognition of his financial support for the taxonomic work and biodiversity research through the BIOPAT-Programme.