Stenocercus guentheri (Boulenger)

Torres-Carvajal, Omar, 2007, A TAXONOMIC REVISION OF SOUTH AMERICAN STENOCERCUS (SQUAMATA: IGUANIA) LIZARDS, Herpetological Monographs 21 (1), pp. 76-178 : 122-123

Stenocercus guentheri (Boulenger) ( Fig. 18 )

Liocephalus guentheri Boulenger, 1885 a:169 . Syntypes: BM 58.7.25.16–18 ; 59.9.20.6 ; 60.6.16.18–21 ; 71.2.7.7–10 ; 71.4.16.53 ; 80.12.8.53 , from ‘‘ Guayaquil [Provincia Guayas, Ecuador], Sarayacu [ Provincia Pastaza ] Ecuador, Western Ecuador, and Colombia̕̕ (restricted to San Antonio de Pichincha , 2500 m, Provincia Pichincha, by Fritts [1974]).

Leiocephalus ornatus ornatus Burt and Burt (part), 1931:271.

Ophryoessoides guentheri Etheridge, 1966:88 ; Peters, 1967:28; Etheridge, in Peters and Donoso-Barros, 1970:214.

Stenocercus guentheri Fritts, 1974:54 ; Ayala, 1986:563; Torres-Carvajal, 2000:17.

Diagnosis.— Stenocercus guentheri differs from all other species of Stenocercus except S. angel , S. chota , S. festae , and S. nigromaculatus by having imbricate scales on posterior surface of thighs, smooth ventrals, a posthumeral mite pocket consisting of a shallow depression with a wide opening (more distinct in adult specimens), small scales on occipitoparietal region, and supraoculars of similar size. Of these species, S. nigromaculatus is unique in having an antehumeral fold. S. guentheri differs from S. angel , S. chota , and S. festae by having smaller scales, which is reflected in relatively higher numbers for most scales counts ( Table 2 ). Males of S. angel and S. chota lack a distinct, transverse black band on ventral surface of neck, which is present in some males of S. guentheri and S. festae . Juveniles of S. festae have distinctly keeled ventrals, which are smooth or weakly keeled in juveniles of S. guentheri . In addition, S. guentheri differs from S. festae by lacking a black antehumeral patch in adult males, which also have lower frequencies of a dark patch on the ventral surface of the neck (50%), and a dark longitudinal midventral mark (66%; 93% in both cases in S. festae ).

Description.—(1) Maximum SVL in males 96 mm (n = 45); (2) maximum SVL in females 73 mm (n = 26); (3) vertebrals 44–64; (4) paravertebrals 59–89; (5) scales around midbody 59–83; (6) supraoculars 5–7; (7) internasals 2–4; (8) postrostrals 4–6; (9) loreals 3–4; (10) gulars 21–31; (11) subdigitals on Finger IV 15–23; (12) subdigitals on Toe IV 22–36; (13) posthumeral mite pocket present as a shallow depression with a wide opening; (14) postfemoral mite pocket distinct with slit-like opening; (15) parietal eye visible through interparietal cornea in 94% of specimens; (16) scales on occipitoparietal region small, keeled or multicarinate, imbricate; (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) neck folds absent; (22) lateral and dorsal nuchals similar in size; (23) posterior gulars rhomboidal, smooth, imbricate, not notched; (24) lateral and dorsal body scales similar in size; (25) vertebrals larger than adjacent paravertebrals; (26) dorsolateral crest absent; (27) ventrals smooth, imbricate; (28) scales on posterior surfaces of thighs keeled, imbricate; (29) inguinal granular pocket absent; (30) inguinal groove absent; (31) preanals not projected; (32) tail not strongly compressed laterally in adult males; (33) tail length 58– 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 50% of adult males; (40) dark midventral longitudinal mark such as faint line, conspicuous stripe, or extensive patch in 66% of adult males; (41) dark patches on ventral surface of thighs in adult males absent; (42) postxiphisternal inscriptional ribs not in contact midventrally, Patterns 1A, 1B, 2A, 2B, 4A, and 4B.

Color in life.—In females, dorsum brown or dark olive-green, with or without scattered dark spots or short, transverse dark marks arranged longitudinally over vertebral line; venter yellow or cream with or without dark flecks. Males exhibit considerable variation in color within and among populations (for more detailed descriptions see Fritts, 1974; Torres-Carvajal, 2000): dorsum olive-green, greenish brown, or dark brown, with or without short, transverse dark marks arranged longitudinally over vertebral line; gular region iridescent pale green, cream, or brown, with or without dark flecks; black patch on ventral surface of neck in some males; ventral body background color grayish blue, greenish gray, bluish green, yellow, or orange, with or without a black or yellow midventral stripe.

Natural History.—Clutch size of S. guentheri is two eggs. Females of this species deposit eggs around May–June ( Fritts, 1974; Torres-Carvajal, 2000). The smallest individual was collected in June 1998 and had a total length of 72 mm (SVL = 20 mm, TL = 52 mm). Fritts (1974) reported one female covering a small hole on the ground containing two eggs, which suggests that there is some degree of parental care in this species. Males tend to occupy rocks or other elevated positions, whereas females are more commonly found on the ground ( Fritts, 1974).

Distribution.— Stenocercus guentheri occurs in the northern Andes between 2 ° 20'S– 0 ° 30'N in Ecuador ( Fig. 9 ). Known from elevations of 2135–3890 m, this species inhabits the upper valleys of several rivers of the Pacific (Río Mira, Río Esmeraldas, and Río Guayas) and Atlantic (Río Pastaza and Río Paute) drainages in Provincias Bolívar, Chimborazo, Cotopaxi, Imbabura, Pichincha, and Tungurahua ( Torres-Carvajal, 2000). Specimens of S. guentheri reported from the Andes of southern Colombia in Departamentos Cauca and Nariño ( Castro and Ayala, 1982; Castro and Granados, 1993; Corredor, 1983) correspond to S. angel .

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.