Stenocercus formosus
Creators: name: Torres-Carvajal, Omar
Publisher: name: Zenodo
Year: 2007
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Squamata
Tropiduridae
Stenocercus
Stenocercus formosus

description: Stenocercus formosus (Tschudi)
(Fig. 18)
Scelotrema formosum Tschudi, 1845:155. Lectotype (Ortiz, 1989): MHNN 2266, a juvenile from ‘‘mountains in central Peru, Río Tulumayo [Departamento Junín], Peru.̕̕
Liocephalus rhodogaster Boulenger, 1901: 547. Syntypes: BMNH 1900.11.27.24–25 (RR 1946.8.29.81–2) from ‘‘La Merced, 3250 ft, Río Perene [Departamento Junín], Perú.̕̕ Synonymy fide Fritts, 1974:51.
Liocephalus lineogularis Werner, 1901 b:3. Holotype: MTD D 1781 from ‘‘Chanchamayo [Departamento Junín], Perú̕̕. Synonymy fide Fritts, 1974:51.
Stenocercus seydi Andersson, 1908:301. Holotype: MWNH 473, a male from ‘‘La Merced [Departamento Junín], 1000 m, Peru̕̕; Burt and Burt, 1933:44. Synonymy fide Fritts, 1974:51.
Leiocephalus formosus Burt and Burt, 1933:27.
Ophryoessoides formosus Etheridge, 1966:88; Etheridge, in Peters and Donoso-Barros, 1970:214.
Stenocercus formosus Fritts, 1974:51.
Diagnosis.— Stenocercus formosus is distinguished from other species of Stenocercus except S. ochoai by having imbricate scales on the posterior surface of thighs, a well-developed postfemoral mite pocket, antehumeral and oblique neck folds, and by lacking an antehumeral mite pocket. S. formosus differs from S. ochoai (character states in parentheses) in having four caudal whorls per autotomic segment (three), keeled dorsal head scales (smooth), lateral and dorsal nuchals similar in size (lateral nuchals less than half the size of dorsal nuchals), more scales (74– 82, X = 77.88) around midbody (56–69, X = 61.83), and pink ventral coloration in adult males (venter black with some yellow laterally).
Description.—(1) Maximum SVL in males 89 mm (n = 5); (2) maximum SVL in females 79 mm (n = 8); (3) vertebrals 58–72; (4) paravertebrals 96–115; (5) scales around midbody 74–82; (6) supraoculars 5–6; (7) internasals 4–5; (8) postrostrals 4–7; (9) loreals 2–5; (10) gulars 24–31; (11) subdigitals on Finger IV 18–21; (12) subdigitals on Toe IV 26–30; (13) posthumeral mite pocket absent; (14) postfemoral mite pocket distinct with slit-like opening; (15) parietal eye not visible through interparietal cornea; (16) scales on occipitoparietal region small, keeled, 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) antehumeral, oblique, postauricular, and supra–auricular neck folds present; (22) lateral and dorsal nuchals similar in size; (23) posterior gulars rhomboidal, smooth or slightly keeled, 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 63–65% of total length; (34) caudal whorls per autotomic segment four; (35) caudals not spinose; (36) dark brown stripe extending anterodorsally from subocular region to supraciliaries always present; (37) dark patch extensively covering gular region in 14% of females; (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 67% of adult males; (41) dark patches on ventral surface of thighs in adult males absent; (42) postxiphisternal inscriptional ribs not in contact midventrally, Pattern 1A (SDSU 1688 identified as Stenocercus arenarius [invalid name] in Torres-Carvajal [2004 a] corresponds to S. formosus.)
Color in life.—Venter in adult males pink with black midventral stripe (Fritts, 1974).
Natural History.— Fritts (1974) observed individuals of this species on the ground, small shrubs, and small rock piles.
Distribution.— Stenocercus formosus is known from the eastern Cordillera of the central Andes in Peru (11 ° S–10 ° S). It occurs at elevations between 1000–1600 m in Departamentos Junín and Pasco (Fig. 12). S. formosus is sympatric with S. boettgeri, S. scapularis, and S. torquatus at María Teresa, 10 ° 42'05"S, 75 ° 27'22"W, 1470 m, Departamento Pasco (Torres-Carvajal et al., 2005). It is also sympatric with S. torquatus at several localities (see Appendix) in Departamento Junín.
Remarks.—The uncertain number and location of type specimens used by Tschudi (1845) to describe Scelotrema formosum and Steironotus arenarius has led some authors to reach taxonomic conclusions that are in conflict with the arrangement presented in this study. Ortiz (1989) proposed Stenocercus (Steironotus) arenarius (Tschudi, 1845) as a junior synonym of ‘‘ Liocephalus rhodogaster ̕̕ and recognized S. formosus as a separate taxon, which he even proposed as a senior synonym of S. ochoai. This was based on examination of different specimens than the ones used by Fritts (1974) to propose the arrangement presented herein. I reject Ortiz̕s, 1989 proposal for three reasons. First, even though Tschudi̕s (1845) descriptions are brief, he listed ‘‘ Steironotus ̕̕ arenarius under the subgenus ‘‘ Eulophus ̕̕, which was described as having an enlarged occipital (interparietal) scale, a diagnostic feature of the Tropidurus Group that is not observed in Stenocercus. In this regard, I find more reasonable Fritts̕ (1974) decision to place ‘‘ Steironotus ̕̕ arenarius in synonymy with ‘‘ Tropidurus tschudi.̕̕ Second, the type locality of ‘‘ Scelotrema ̕̕ formosum lies in the same area (i.e., eastern Andean slopes in central Peru) as the type locality of ‘‘ L. rhodogaster ̕̕, as well as the localities of all subsequently collected specimens of Stenocercus formosus sensu Fritts (1974). In contrast, the type locality of ‘‘ Steironotus ̕̕ arenarius lies far away on the opposite side of the Andes, and no species of Stenocercus is known to have such a disjunct distribution on both sides of the Andes. Third, the ventral coloration of ‘‘ Scelotrema ̕̕ formosum was described as violet (Tschudi, 1845), which is characteristic of males of Stenocercus formosus sensu Fritts (1974). Regarding the proposed synonymy between S. ochoai and S. formosus, males of the former species have dull black venters (Fritts, 1972), which among other features makes S. ochoai very distinct from S. formosus.
description: Published as part of Torres-Carvajal, Omar, 2007, A TAXONOMIC REVISION OF SOUTH AMERICAN STENOCERCUS (SQUAMATA: IGUANIA) LIZARDS, pp. 76-178 in Herpetological Monographs 21 (1) on pages 119-121, DOI: 10.1655/06-001.1, http://zenodo.org/record/14384794