Stenocercus nigrocaudatus, Venegas & García-Ayachi & Chávez-Arribasplata & García-Bravo, 2022

Venegas, Pablo J., García-Ayachi, Luis A., Chávez-Arribasplata, Juan C. & García-Bravo, Antonio, 2022, Four new species of polychromatic spiny-tailed iguanian lizards, genus Stenocercus (Iguania: Tropiduridae), from Peru, Zootaxa 5115 (1), pp. 1-28 : 15-18

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.

Figures

FIGURE 3. Distribution map of Stenocercus asenlignus sp. nov., Stenocercus leybachi sp. nov., S. nigrocaudatus sp. nov., and S. qalaywasi sp. nov., and the similar species: S. arndti, S. carrioni, S. chlorostictus, S. crassicaudatus, S. empetrus, S. eunetopsis, S. flagracanthus, S. simonsii, and S. torquatus. The symbols of species with a black spot in the centre correspond to type localities. Black dots correspond to important cities for reference.

FIGURE 6. Stenocercus nigrocaudatus sp. nov. preserved holotype, adult male, SVL 57 mm (CORBIDI 19768): dorsal (A), lateral (B), and ventral (C) views of the head; dorsal (D) and ventral (E) views of the entire specimen. Photographs by LAGA. Scale bar = 10 mm.

FIGURE 7. Dorsolateral and ventral views of Stenocercus nigrocaudatus sp. nov. in life: (A-C) holotype, SVL 57 mm (CORBIDI 19768); (D, E) adult male, SVL 56 mm (CORBIDI 19767); (F, G) adult male, SVL 69 mm (CORBIDI 19769); (H-J) adult female, SVL 76 mm (CORBIDI 19765); (K) adult male basking in a tree (CORBIDI 19767); (L) adult male basking on a house wall (not collected). Photographs by (A-J) JCCA, and (K-L) PJV.