Stenocercus chrysopygus Boulenger, 1900

Torres-Carvajal, Omar, 2007, A TAXONOMIC REVISION OF SOUTH AMERICAN STENOCERCUS (SQUAMATA: IGUANIA) LIZARDS, Herpetological Monographs 21 (1), pp. 76-178 : 100-101

Stenocercus chrysopygus Boulenger

( Fig. 14 )

Stenocercus chrysopygus Boulenger, 1900: 183 . Syntypes: BMNH 1900.6.20.8–17 (RR 1946.8.9.33–46 from ‘‘ Carao [Caraz], 8000 ft, Peru ̕̕, BMNH 1900.6.20.18 (RR 1946.8.11.84) from ‘‘ Huaraz , 10,000 ft, Peru ̕̕, and BMNH 1900.6.20.19 (RR 1946.8.5.98) from ‘‘ Recuay , 11,000 ft, Peru̕̕ (restricted to Huaraz , 10,000 ft, Departamento Ancash, Peru, by Fritts [1974]); Burt and Burt, 1933:42; Etheridge, in Peters and Donoso-Barros, 1970:256; Fritts, 1974:42.

Diagnosis.— Stenocercus chrysopygus is distinguished from other species of Stenocercus except S. cupreus , S. latebrosus , S. modestus , S. orientalis , and S. ornatissimus by having granular scales on the posterior surface of thighs, conspicuous antehumeral and oblique neck folds, a distinct mite pocket under oblique neck fold, and by lacking a vertebral crest. Of these species, S. latebrosus and S. ornatissimus are unique in having deep neck mite pockets under the antehumeral and oblique neck folds, whereas S. orientalis is unique in having prominently keeled dorsal head scales. S. chrysopygus can be distinguished from S. cupreus and S. modestus (character states in parentheses) by having granular or smooth and subimbricate scales on the lateral aspect of neck (keeled and imbricate), and by lacking caudal notches on ventral scales (caudal notch on ventrals present). In addition, S. chrysopygus has more vertebrals (54–86, X = 66.01) and more scales around midbody (48–82, X = 64.31) than S. cupreus (44–58, X = 51.53 and 51–66, X = 59.47, respectively) and S. modestus (39– 46, X = 42.00 and 32–38, X = 35.17, respectively).

Description.—(1) Maximum SVL in males 76 mm (n = 49); (2) maximum SVL in females 69 mm (n = 55); (3) vertebrals 54–86; (4) paravertebrals 52–85; (5) scales around midbody 48–82; (6) supraoculars 4–8; (7) internasals 2–5; (8) postrostrals 4–6; (9) loreals 1–3; (10) gulars 19–27; (11) subdigitals on Finger IV 16–23; (12) subdigitals on Toe IV 22–30; (13) posthumeral mite pocket present as one or more vertical folds or ridges; (14) postfemoral mite pocket distinct with slit-like opening; (15) parietal eye always visible through interparietal cornea; (16) scales on occipitoparietal region small, smooth, slightly imbricate or juxtaposed; (17) projecting angulate temporals absent; (18) row of enlarged supraoculars occupying most of supraocular region absent; (19) scales on frontonasal region weakly imbricate anteriorly; (20) preauricular fringe present; (21) antehumeral, longitudinal, oblique, and postauricular neck folds present; (22) lateral nuchals less than half the size of dorsal nuchals; (23) posterior gulars cycloid, smooth, slightly imbricate, notched; (24) lateral and dorsal body scales similar in size; (25) vertebrals and adjacent paravertebrals similar in size; (26) dorsolateral crest absent; (27) ventrals smooth, imbricate; (28) scales on posterior surfaces of thighs granular; (29) inguinal granular pocket absent; (30) inguinal groove absent; (31) preanals not projected; (32) tail not compressed laterally in adult males; (33) tail length 60–69% of total length; (34) caudal whorls per autotomic segment three; (35) caudals not spinose; (36) dark brown stripe extending anterodorsally from subocular region to supraciliaries absent; (37) dark patch extensively covering gular region of females present; (38) dark patch extensively covering gular region of adult males present; (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 59% of adult males; (41) dark patches on ventral surface of thighs in 61% of adult males; (42) postxiphisternal inscriptional ribs not in contact midventrally, Patterns 2B, 2C, and 3.

Color in life.—Males of this species exhibit considerable variation in color within and among populations (for more detailed descriptions see Cadle, 1998; Fritts, 1974; Schlüter, 1999 b, 2000 a, 2001 a, 2005). For instance, the ventral aspect of the body between fore limbs and hind limbs varies from grayish white to black; ventrally, the pelvic region and thighs are yellow or black; the chin and gular region are blue with black reticulations or cream with blue suffusion and gray blotches. Most females have a gray middorsal stripe and a whitish-beige venter with scattered gray flecks ( Fritts, 1974).

Natural History.— Schlüter (1999 b, 2000 b) reported clutch sizes of 5–6 eggs from two captive females collected in the western slopes of Cordillera Blanca in Peru. These eggs were laid only in October during two consecutive years suggesting that this species reproduces once a year. Incubation time varied between 103–110 days at 24–25 C; hatchlings varied in size between 25–27 mm SVL. Fritts (1974) observed most males on small rocks or mud walls, and most females under rocks or at the base of small shrubs.

Distribution.— Stenocercus chrysopygus occurs in the central Andes (10 ° S–8 ° S) at elevations between 2265–3500 m ( Fig. 15 ). It is known from the upper valleys of Ríos Chiquián and Santa (Pacific drainage), and Río Marañón (Atlantic drainage) on the western and eastern Cordilleras of Peru in Departamentos Ancash and Huánuco.

Remarks.—Several differences in scale counts and coloration among populations of S. chrysopygus from both Pacific and Atlantic drainages have been reported ( Cadle, 1998; Fritts, 1974; Schlüter, 2000 a). However, no morphological diagnostic characters supporting the split of these populations into more than one species have been proposed. Although more collections from some populations are needed, phylogeographic studies using DNA might be more appropriate to better assess the history and taxonomic status of populations of S. chrysopygus .

Figures

FIG. 14.—Eight species of Stenocercus. (A) S. chota (LAC); (B) S. chrŋsopŋgus (MLU); (C) S. crassicaudatus (WED); (D) S. cupreus (MLU); (E) S. doellojuradoi (JAS); (F) S. dumerilii (TAP); (G) S. empetrus (RON); (H) S. festae (OTC).

FIG. 15.—Distribution of four species of Stenocercus in Peru.