Stenocercus humeralis (Günther)

Torres-Carvajal, Omar, 2007, A TAXONOMIC REVISION OF SOUTH AMERICAN STENOCERCUS (SQUAMATA: IGUANIA) LIZARDS, Herpetological Monographs 21 (1), pp. 76-178 : 125-127

Stenocercus humeralis (Günther) ( Fig. 18 )

Microphractus humeralis Günther, 1859 a:90 . Syntypes: BM 1946.8.11.76–77 , from ‘‘Andes of Ecuador̕̕ (restricted to Loja , 2150 m, Provincia Loja, Ecuador, by Fritts [1974]).

Stenocercus humeralis Boulenger, 1885 a:134 ; Burt and Burt, 1931:288; Burt and Burt, 1933:43; Peters, 1967:34; Etheridge, in Peters and Donoso-Barros, 1970:256; Fritts, 1974:56; Torres-Carvajal, 2000:22.

Diagnosis.— Stenocercus humeralis is distinguished from other species of Stenocercus except S. boettgeri , S. haenschi , and S. varius by having granular scales on the posterior surface of thighs, enlarged vertebrals, three caudal whorls per autotomic segment, a medially complete antegular fold, non-spinose caudals, and by males lacking a black transverse band on the ventral surface of neck. S. humeralis differs from these species (character states in parentheses) by having 98–125 (X = 110.05) scales around midbody (79–104, X = 88.61 in S. boettgeri ; 57–64, X = 60.50 in S. haenschi ; 74–88, X = 82.35 in S. varius ), 81– 112 (X = 92.21) vertebrals (64–93, X = 76.86 in S. boettgeri ; 50 in S. haenschi ; 60–85, X = 69.53 in S. varius ) lateral and dorsal nuchals similar in size (lateral nuchals less than half the size of dorsal nuchals), and a black antehumeral dorsal collar in adult males (antehumeral collar absent).

Description.—(1) Maximum SVL in males 112 mm (n = 15); (2) maximum SVL in females 108 mm (n = 15); (3) vertebrals 81– 112; (4) paravertebrals 106–148; (5) scales around midbody 98–125; (6) supraoculars 6–9; (7) internasals 3–4; (8) postrostrals 4–7; (9) loreals 2–4; (10) gulars 41–68; (11) subdigitals on Finger IV 24–33; (12) subdigitals on Toe IV 28–41; (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 not visible through interparietal cornea; (16) scales on occipitoparietal region small, smooth, juxtaposed; (17) projecting angulate temporals absent; (18) row of enlarged supraoculars occupying most of supraocular region absent; (19) scales on frontonasal region juxtaposed; (20) preauricular fringe present; (21) antegular (continuous medially), antehumeral, gular, longitudinal, oblique, postauricular, and supra-auricular neck folds present; (22) lateral and dorsal nuchals similar in size; (23) posterior gulars cycloid, smooth, slightly imbricate, not notched; (24) lateral scales reduced in size, approximately half the size of dorsal body scales; (25) vertebrals larger than adjacent paravertebrals; (26) dorsolateral crest absent; (27) ventrals smooth, imbricate; (28) scales on posterior surfaces of thighs granular; (29) inguinal granular pocket present; (30) inguinal groove present; (31) preanals not projected; (32) tail not compressed laterally in adult males; (33) tail length 62–68% 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 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) dark patches on ventral surface of thighs in adult males absent; (42) postxiphisternal inscriptional ribs not in contact midventrally, Patterns 1A, 1B, 2B, and 2C.

Color in life.—Dorsum yellowish green with scattered black flecks or yellow spots that form transverse rows in some males; short, black, middorsal transverse marks arranged longitudinally over vertebral line in some specimens; black antehumeral collar in most adult males; venter pale yellow ( Torres-Carvajal, 2000).

Natural History.—Four enlarged oviductal eggs (two in each oviduct) were reported from a large female (SVL = 90 mm) collected in December 1968; the smallest individual was collected in October 1996 and had a total length of 118 mm (SVL = 40 mm, TL = 78 mm; Torres-Carvajal, 2000). Fritts (1974) observed this species on small shrubs, eucalyptus tree trunks, and Agave plants; I also have observed this species on large rock walls in mesic habitats.

Distribution.— Stenocercus humeralis occurs in the northern Andes at elevations of 2000–3000 m in Provincia Loja, southern Ecuador ( Fig. 9 ). This species inhabits the upper valleys of Río Catamayo (Pacific drainage) and Río Zamora (Atlantic drainage) between 4 ° S–3 ° S. It occurs in sympatry with S. ornatus in the upper valley of Río Zamora.

Figures

FIG. 18.—Eight species of Stenocercus. (A) S. fimbriatus (JCA); (B) S. formosus (MLU); (C) S. guentheri (LAC); (D) S. humeralis (OTC); (E) S. imitator (PVE); (F) S. iridescens (RWM); (G) S. lache (JMR); (H) S. limitaris (PVE).

FIG. 9.—Distribution of six species of Stenocercus in Ecuador.