Stenocercus nigrobarbatus, Venegas & Echevarría & García-Ayachi & Landauro, 2020

Venegas, Pablo J., Echevarría, Lourdes Y., García-Ayachi, Luis A. & Landauro, Caroll Z., 2020, Two new sympatric species of Stenocercus (Squamata: Iguania) from the inter- Andean valley of the Mantaro River, Peru, Zootaxa 4858 (4), pp. 555-575 : 564-571

Stenocercus nigrobarbatus sp. nov.

Figures 6–10 , Table 1.

Holotype. CORBIDI 13725 , adult male from Fundición (12°17’36.41”S, 74°39’39.67” W) at 2,158 m asl, Tayacaja Province, Huancavelica Region, Peru, collected on January 31, 2014 by L. Y. Echevarría.

Paratypes. Peru: Huancavelica Department: Tayacaja Province : CORBIDI 13637 a juvenile female from Jatuspata (12°15’14.617’’ S, 74°41’ 16.93’’ W) at 2,972 m asl, collected on September 3, 2013 by C. Landauro ; CORBIDI 13638 a juvenile female from Pichiu (12°19’11.815’’ S, 74°39’3.588’’ W) at 2,036 m asl, collected on September 13, 2013 by C. Landauro ; CORBIDI 13640 juvenile female from Pichiu , collected on September 12, 2013 by C. Landauro ; CORBIDI 13641 adult female from Barropata (12°17’21.943’’ S, 74°41’19.035’’ W) at 1,725 m asl, collected on October 2, 2013 by C. Landauro ; CORBIDI 13639 and CORBIDI 13642 female juveniles from Fundición (12°17’32.347’’ S, 74°39’45.433’’ W), at 2,169 m asl, collected on September 28, 2013 by C. Landauro ; CORBIDI 13718 adult male from Chupto (12°19’52.96” S, 74°39’13” W) at 2,058 m asl, collected on January 23, 2014 by L. Y. Echevarría ; CORBIDI 13719 adult male from Chupto (12°18’22.19” S, 74°39’18.42” W) at 2,314 m asl, on January 24, 2014 by L. Y. Echevarría ; CORBIDI 13722 adult female from Chupto (12°19’52.96” S, 74°39’13” W) at 2,058 m asl, collected on January 21, 2014 by L. Y. Echevarría ; CORBIDI 13728 adult female from Barropata (12°17’34.95” S, 74°41’34.08” W) at 1,704 m asl, collected on February 2, 2014 by L. Y. Echevarría ; CORBIDI 13729 adult female from Barropata (12°17’22.11” S, 74°41’19.07” W) at 1,783 m asl, collected on February 3, 2014 by L. Y. Echevarría ; CORBIDI 14669 adult female from Chupto (12°18’48.18” S, 74°39’1.83” W) at 2,345 m asl, collected on July, 1 2014 by L. Y. Echevarría ; CORBIDI 14674 adult female from type locality, collected on July 6, 2014 by L. Y. Echevarría; CORBIDI 14676 juvenile female and CORBIDI 14677 adult male from Barropata (12°17’37.66” S, 74°41’39.18” W) at 1,693 m asl, collected on July 7, 2014 by L. Y. Echevarría ; CORBIDI 15765–66 (adult male and female, respectively) and CORBIDI 15767 (juvenile male) from Pichiu (12°15’31.57” S, 75°6’3.6” W) at 2,206 m asl, collected on January 14, 2015 by L. Lujan ; CORBIDI 16033 adult male from Pichiu (12°19’50” S, 74°39’13.07” W) at 2,090 m asl, collected on July 9, 2015 by J. Malqui ; CORBIDI 20546–47 two adult males from San Luis de Estanque (12º19’8.62” S, 74º44’24.19” W) at 2,636 m asl., collected on Jun 17, 2019 by L.A. García-Ayachi .

Diagnosis. Adult males of Stenocercus nigrobarbatus can be easily distinguished from all species of Stenocercus by having a continuous black patch covering the infralabials, throat, chest, ventral surfaces of forelimbs, belly (as a black midventral line), ventral surfaces of hind limbs, and pelvic region ( Figs. 6B , 8B , 9B and 9C ).

However, among the 69 currently described species of Stenocercus , S. nigrobarbatus resembles S. frittsi Torres-Carvajal, 2005 , and S. variabilis Boulenger, 1901 , by the following combinations of characters: (1) granular scales on the posterior surface of thighs, (2) imbricate and keeled lateral body scales, (3) a distinct row of enlarged vertebral scales, (4) unnotched gular scales, (5) three caudal whorls per autotomic segment, (6) brown dorsal ground color, and (7) distinct oblique neck fold, and antegular fold not continuous medially.

Stenocercus nigrobarbatus differs from the geographically close S. frittsi (character state of latter in parenthesis) by having a postfemoral mite pocket composed by one or more vertical folds or ridges, Type 1 of Torres-Carvajal (2007a) (postfemoral pocket absent in S. frittsi ), 2–4 postrostrals (5–7), and two pairs of postxiphisternal inscriptional ribs, long, not in contact midventrally, pattern 1A of Torres-Carvajal (2004) (three pairs of postxiphisternal inscriptional ribs, two pairs long and the last pair short, not in contact midventrally; pattern 2B of Torres-Carvajal 2004).

Stenocercus nigrobarbatus can be distinguished from S. variabilis (character state in parenthesis) by having 2–4 postrostrals (6), postfemoral pocket composed by one or more vertical folds or ridges, Type 1 of Torres-Carvajal (2007a) (slit-like opening, Type 2 of Torres-Carvajal 2007a), and inguinal groove absent (present). In addition, lateral body scales in S. nigrobarbatus are slightly smaller than dorsals, while S. frittsi and S. variabilis have lateral body scales approximately half the size of dorsals.

Characterization. (1) Maximum SVL in males 67.73 mm (n = 4); (2) maximum SVL in females 62.29 mm (n = 5); (3) vertebrals 47–73; (4) paravertebrals 69–87; (5) scales around midbody 57–74; (6) supraoculars 5–7; (7) internasals 3–5; (8) postrostrals 2–4; (9) loreals 3–7; (10) gulars 19–30; (11) lamellae on Finger IV 18–23; (12) lamellae on Toe IV 27–34; (13) posthumeral pocket as one or more vertical folds or ridges, Type 1 of Torres-Carvajal (2007a); (14) postfemoral pocket composed by one or more vertical folds or ridges, Type 1 of Torres-Carvajal (2007a); (15) parietal eye not visible; (16) occipital scales small, smooth, juxtaposed; (17) no projecting angulate temporals; (18) supraoculars of varying sizes; (19) scales in frontonasal region slightly imbricate anteriorly; (20) short preauricular fringe present; (21) antehumeral, antegular, gular, oblique, suprauricular and postauricular neck folds present; (22) nuchal mite pocket absent; (23) lateral nuchals less than half size of dorsal nuchals; (24) posterior gulars in adults smooth, imbricate, not mucronate; (25) lateral scales slightly smaller than dorsal body scales; (26) vertebrals larger than adjacent paravertebrals; (27) dorsolateral crest absent; (28) ventrals in adults smooth, imbricate, not mucronate; (29) scales on posterior surfaces of thighs granular; (30) inguinal granular pocket absent; (31) inguinal groove absent; (32) preanals not projecting; (33) tail not compressed laterally in adult males; (34) tail length 62–70% of total length; (35) three caudal whorls per autotomic segment; (36) caudals not spinose; (37) dark stripe extending anterodorsally from subocular region to supraciliaries present; (38) gular region of adult females dark or densely pigmented in all specimens; (39) gular region of adult males dark or densely pigmented in all specimens; (40) black blotch on ventral surface of neck in adult males absent; (41) bold black midventral line present in males; (42) black patch on ventral surface of thighs present in males; (43) dorsal ground color brown, in females and males; and (44) postxiphisternal inscriptional ribs not articulating midventrally, both pairs long, Pattern 1A of Torres-Carvajal (2004).

Description of holotype. Male ( Fig. 6-8 ); SVL= 66.02 mm; TL = 130.0 mm; maximum head width = 12.24; head length = 15.87; head height = 8.63; scales on parietal and occipital regions small, smooth, juxtaposed; parietal eye not visible; supraoculars in six rows, smooth, slightly imbricate, of varying sizes; canthals two; anterior most canthal separated from nasal by one minute scale; scales in frontonasal region slightly imbricate; internasals four; postrostrals three, subequal in size, wider than long; supralabials seven; infralabials seven; loreals six; lorilabials in one row; preocular not divided, in contact with posterior canthal; lateral temporals imbricate, weakly keeled; gulars in 29 rows between tympanic openings; all gulars smooth, imbricate; second infralabial in contact with first two sublabials; mental in contact with first pair of infralabials and first pair of postmentals; lateral and dorsal scales of body and dorsal scales of neck keeled, imbricate; lateral scales of neck granular; scales around midbody 63; vertebrals large, in 68 rows, not forming a prominent serrate vertebral crest; paravertebrals 86; ventrals smooth, imbricate; preauricular fringe short, composed of two enlarged scales, both same size; antehumeral, antegular, gular, oblique, suprauricular, postauricular neck folds and ventrolateral body fold present; limb scales keeled, imbricate; ventral scales of hind limbs and upper arms smooth; lamellae on Finger IV 23; lamellae on Toe IV 31; tail not compressed laterally; caudals keeled, imbricate; basal subcaudals smooth, imbricate; vertebral crest extending more than half length of tail; tail length 1.9 times SVL; posthumeral pocket shallow (Type 1 Torres-Carvajal 2007a) with vertically oriented fold approximately 2.57 mm long; postfemoral pocket composed by one vertical fold (type 1 of Torres-Carvajal 2007a); postfemoral region composed of imbricate, smooth scales, becoming smaller toward insertion of hind limbs ( Fig. 10A ).

Color in life of the holotype. Dorsal surfaces of head and neck cinnamon brown with yellow spots, denser on neck; lorilabials and supralabials yellow; infralabials black; ventrolateral regions of head and neck black; dorsal surfaces of body, limbs and tail dusty brown with pale yellow spots; flanks light blue, densely covered with cream spots; limbs and tail with thin dark brown marks on dorsal surfaces ( Fig. 8A ). Ventral surface of head, throat, chest black; ventral surfaces of forelimbs black, although pigmentation is faint at elbow joint; a bold black midventral line, continuous with chest pigmentation, flanked by pink; ventral surfaces of hind limbs, and pelvic region black, except by the cloaca; posterior surfaces of thighs pink; pre-cloacal region dark yellow and post post-cloacal region pink; ventral surface of tail pink, with a yellow blotch and blackish speckles at the base ( Fig. 8B ). All black pigmentation on ventral surfaces constitutes a continuous patch, except black pigmentation on tail.

Coloration of holotype in ethanol 70%. Dorsally, all yellow spots turned to pale yellow. Dorsal surfaces of head and neck turned brown. Ventrally, pink and yellow pigmentation turned to a less vivid (pale) shade, almost vanished on cloaca.

Variation. Scale counts and measurements for Stenocercus nigrobarbatus are presented in Table 1. Loreals 3–7; supralabials 6–8; infralabials 5–8; postrostrals 2–4; second infralabial not in contact third sublabial in all specimens; first pair of postmentals in contact in all specimens.

Dorsal coloration in adult males of Stenocercus nigrobarbatus is the same in all adult male paratypes (n = 5) ( Fig. 9A ). The black coloration on ventral surfaces as a continuous patch is exclusive to adult males ( Fig. 9 B– C). The juvenile specimen CORBIDI 13718 has a faint black midventral line on the belly ( Fig. 9 D–E). Another juvenile specimen ( CORBIDI 13719 ) has the gular region and ventral surface of neck covered by a dark gray patch and the midventral region of the belly has scattered dark gray dots ( Fig. 9 F–G). These immature males ( CORBIDI 13718 and 13719) have the pelvic region and the base of tail yellow and the ventral surface of forelimbs cream ( Fig. 9 D–G). In both specimens the pink coloration on the flanks of the belly is also less intense than in the holotype. In the adult male paratype ( CORBIDI 20547 ) the base of the tail has a black blotch and the pre-cloacal region is yellow with black speckles ( Fig. 9C ) .

Sexual dimorphism is evident in coloration and size (maximum SVL in males 67.0 mm versus 62.0 mm in females). Dorsal coloration in adult females can be gray or brown with irregular dark brown blotches over the vertebral line and a light brown dorsolateral stripe from the temporal region to the base of tail ( Fig. 9H ); dorsal surface of limbs has dark brown or gray transversal bars; sides of head brown or gray with a thin postocular stripe and some scattered dark brown dots; sides of neck yellowish brown with light yellow flecks; jaw and ventrolateral region of neck black or dark gray; body flanks covered by a dark brown reticulation. Ventrally all adult females have the gular region and neck dark gray, belly and limbs are light cream, and the tail is light orange ( Fig. 9I ).

Juvenile females, between 43.0–51.0 mm of SVL, have the same dorsal and ventral pattern than adult females, only two specimens (CORBIDI 13637 and 13642) have the gular region gray with dark gray speckles, and chest and belly light cream with gray speckles. The smallest juvenile female (CORBIDI 14676) has the gular region covered by gray flecks. The juvenile male CORBIDI 13640 (SVL = 43.0 mm) has the dorsum with dark brown dorsal marks as adult and juvenile females, however, the gular region and chest are gray and the belly is grayish cream. The juvenile male CORBIDI 15767 (SVL = 53.0 mm) has the same dorsal coloration as adult males but ventrally the gular region and chest are gray, and has a faint gray midventral line on belly flanked by a weak pink hue; pelvic region, ventral surface of hindlimbs and tail are light cream.

Distribution and natural history observations. Stenocercus nigrobarbatus is known from four localities in SDF of the Mantaro River Valley at elevations between 1,693 and 2,345 m asl, Huancavelica Department, Peru ( Fig. 5 ). Stenocercus nigrobarbatus inhabits a seasonal dry forest, according to classification of Linares-Palomino (2004), and Central Andean Yungas according to Olson et al. (2001). In most localities the habitat has been modified by crops of Zea mays , Opuntia , and Persea sp., roads and the construction of a hydroelectric plant. However, this species is very conspicuous in most localities.

Specimens of Stenocercus nigrobarbatus were found inactive under rocks during cloudy days and active, basking or running, during warm days, among rocks, cacti or shrubs. Other species of Squamate reptiles collected at the same localities of S. nigrobarbatus include Ameiva reticulata , Epictia sp., Mastigodryas boddaerti , Micrurus sp., and Oxyrhopus cf. erdisii , and Stenocercus diploauris .

Etymology. The specific epithet “ nigrobarbatus ” is a noun derived from the Latin words “ nigro ” (= black) and “ barbatus ” (= bearded). It refers to the black patch covering the gular region and ventral surface of neck, including the jaw angle, of adult males which resembles a black beard.

Figures

FIGURE 5. Distribution map of six species of Stenocercus from Peru. S. diploauris sp. nov. (pentagons), S. formosus (squares), S. frittsi (crosses), S. nigrobarbatus sp. nov. (triangles), S. ochoai (circles), and S. variabilis (diamonds). Symbols with a dot in the middle correspond to type localities.

FIGURE 6. Stenocercus nigrobarbatus sp. nov., holotype CORBIDI 13725, male, 66.02 mm SVL. Dorsal (A) and ventral (B) views. Photographs by P.J. Venegas. Scale bar = 10 mm.

FIGURE 7. Dorsal (A), lateral (B), and ventral (C) views of the head of Stenocercus nigrobarbatus sp. nov. holotype, COR- BIDI 13725, male. Photographs by P.J. Venegas. Scale bar = 10 mm.

FIGURE 8. (A) Dorsolateral and (B) ventral views of the holotype of Stenocercus nigrobarbatus sp. nov. (CORBIDI 13725) in life. Photographs by L.Y. Echevarría.

FIGURE 9. Paratypes of Stenocercus nigrobarbatus sp. nov.: (A, B) dorsolateral and ventral views of an adult male (CORBIDI 20546); (C) ventral view of an adult male (CORBIDI 20547); (D, E) dorsolateral and ventral views of an immature male (COR- BIDI 13718); (F, G) dorsolateral and ventral views of an immature male (CORBIDI 13719); (H, I) dorsolateral and ventral views of an adult female (CORBIDI 13729). Photographs A-C by L.A. García-Ayachi and D-I by L.Y. Echevarría.

FIGURE 10. Variation of the postfemoral mite pocket in Stenocercus nigrobarbatus sp. nov., right views of (A) holotype (COR- BIDI 13725), (B) adult male (CORBIDI 14677), and (C) adult female (CORBIDI 14669). Photographs by P.J. Venegas. Scale bar = 5 mm.