Thursday, February 18, 2021

[Herpetology • 2021] Stenocercus ica • A New Species of the Genus Stenocercus (Iguania: Tropiduridae) from the Peruvian Pacific Coast (Ica Region)

Stenocercus ica 
Mendoza, Ramírez, Barrera & Aguilar-Puntriano, 2021

Photos by A. Mendoza.

 A new species of the genus Stenocercus is described from the Peruvian coastal desert in the Ica region. The new species is similar in ecology and morphology to Stenocercus modestus, but differs from it in lacking an oblique neck fold, a distinct patch of small scales posterior to the lateral region of the neck, and bright yellow lateral dots on the head and body in males. The new species also has more subdigital lamellae on the fourth toe than S. modestus, and females exhibit a wide dark stripe between the subocular and antehumeral regions, as well as dark reticulations in the gular region. Distribution models of the new species and S. modestus suggest no geographical overlap. In conclusion, morphology and species distribution models strongly imply the new Stenocercus species to be an undescribed lineage and different from all other species of the genus. This new species is the most southerly distributed Stenocercus in the Pacific coastal desert of Peru thus far. We propose the new species be classified as ‘Endangered’ based on its area of occupancy and threat-defined locations. 

Key words. Squamata, new species, coastal desert, distribution model, taxonomy. 

 Coloration in life of Stenocercus ica sp. n.:
dorsolateral view of adult male holotype (MUSM 40418);
dorsolateral view of adult female paratype (MUSM 40415).
Photos by A. Mendoza.

 Stenocercus ica sp. n.
Adult male (MUSM 39364, SVL 81.5 mm) from Arrabales (Ica region).
Photos by A. Mendoza.

Stenocercus ica sp. n.

Diagnosis: (1) Maximum SVL in males 81.5 mm (N = 5); (2)  maximum SVL in females 62.3 mm (N = 4); (3) vertebrals 44–48 (N = 11); (4) paravertebrals 44–48 (N = 11); (5) scales around midbody 35–38 (N = 11); (6) supraoculars 5–6 (N = 11); (7) internasals 2–4 (N = 11); (8) postrostrals 2–5 (N = 11); (9) loreals 1–3 (N = 11); (10) gulars 15–19 (N = 11); (11) lamellae on Finger IV 20–23 (N = 11); (12) lamellae on Toe IV 28–32 (N = 11); (13) posthumeral mite pockets absent (Type I of Torres-Carvajal 2007b); (14) postfemoral mite pockets present (Type II de Torres-Carvajal 2007b); (15) parietal eye visible; (16) smooth, juxtaposed, or slightly imbricate occipital scales; (17) projecting angular temporals absent; (18) enlarged supraoculars occupying most of the supraocular region in one row absent; (19) scales in the frontonasal region smooth, weakly imbricate anteriorly or juxtaposed (20) preauricular fringe present; (21) antehumeral and longitudinal folds present; (22) lateral nuchals similar in size to dorsal nuchals; (23) posterior gulars smooth, cycloid, imbricate , with or without notches or apical pits; (24) a caudad notch on ventral scales; (25) lateral body scales similar in size to dorsal scales; (26) vertebrals similar in size to adjacent dorsals; (27) dorsolateral crests absent; (28) ventrals smooth, imbricate, sub-rhomboidal, similar in size to dorsals; (29) scales on the posterior faces of thighs granular; (30) prefemoral fold absent; (31) inguinal groove absent; (32) preanals not projected; (33) tail slightly compressed laterally in adult males; (34) tail length 70–73% of total length; (35) three caudal whorls per autotomic segment; (36) caudals not spinose; (37) dark stripe from the subocular region to superciliars absent; (38) colour pattern of dark reticulations in the gular region in adult females; (39) dark streaks that form a reticulum in the gular region in adult males absent; (40) black spot on ventral face of neck in adult males absent; (41) dark midventral stripe in adult males absent; (42) black patches on ventral faces of thighs in adult males absent; (43) background colour of dorsum olive yellowish to brown in life.

Etymology. The specific epithet ica is a noun in apposition and refers to the Ica region of Peru where all type specimens were collected. It also refers to Ica as being the southernmost distribution record for the genus on the Peruvian Pacific coast. 

Distribution: Stenocercus ica sp. n. is as yet only known from the valley of the Ica river basin, with the highest number of individuals recorded at two localities (Arrabales and Ocucaje) in the Ica region between 300 to 450 m a.s.l. on the Peruvian Pacific coast. Stenocercus ica sp. n. appears to be restricted to low altitudes (Figs 6–7). 

Natural history: Stenocercus ica sp. n. has been found in dense shrub vegetation close to riverside forest and the irrigation installations in agricultural areas in the Ica river basin (Fig. 5A). Specimens were observed basking at the edge of a bushy area, mainly on dry leaf litter, fallen branches, and on the, usually in dappled or diffused sunlight. Two specimens were observed escaping into holes at the base of bushes, under accumulations of leaf litter. This species probably utilizes these cavities as burrows and nests. 

Alejandro Mendoza, César Ramírez, Diego Barrera and César Aguilar-Puntriano. 2021. A New Species of the Genus Stenocercus (Iguania: Tropiduridae) from the Peruvian Pacific Coast (Ica Region). SALAMANDRA. 57(1); 1-14.

Resumen. Se describe una nueva especie del género Stenocercus del desierto costero peruano en el Departamento de Ica. La nueva especie es similar en ecología y morfología a Stenocercus modestus, pero difiere al carecer de un pliegue oblicuo en el cuello, un parche visible de pequeñas escamas posteriores a la región lateral del cuello y puntos amarillos brillantes sobre la cabeza y el cuerpo en los machos. La nueva especie también tiene un mayor número de lamelas subdigitales en el cuarto dedo de la pata posterior que S. modestus, y las hembras muestran una ancha franja oscura entre la región subocular y antehumeral, así como reticulaciones oscuras en la región gular. Los modelos de distribución de la nueva especie y S. modestus no muestran superposición en sus distribuciones potenciales. En conclusión, la morfología y los modelos de distribución de especies sugieren fuertemente que la nueva especie de Stenocercus es un linaje no descrito y diferente de otras especies del género. La nueva especie es el registro más sureño de su género en el desierto costero del pacifico en Perú. Así mismo, recomendamos que se clasifique como En peligro basado en el área de ocupación y localidades con amenazas.
Palabras clave. Squamata, desierto costero, modelo de distribución, taxonomía.