QCAZ 10670 (Figs 1, 2), an adult male from Nanegal, Santa Lucia Cloud Forest Reserve, 0.113528°N; -78.6135°W (Decimal Degrees, WGS84), 1742 m, Provincia Pichincha, Ecuador, collected on 27 June 2010 by V. Aguirre-Peñafiel and J. Zanka.

(11). ECUADOR: Provincia Pichincha: QCAZ 9738, Mindo, Hacienda San Vicente, -0.050720°N, -78.772350°W (DD), 1246 m, collected on 7 August 2009 by S. Poe, E. Schaad, I. Latella, N. Blea, T. Kennedy and F. Ayala-Varela; QCAZ 10821, 10826, Nanegal, Santa Lucía Cloud Forest Reserve, 0.117780°N, -78.607555°W (DD), 1580 m, collected on 9 March 2010 by B. Tolhurst, P. Mafla-Endara, S. Ryan and X. Cueva; QCAZ 11854–55, Nanegal, Santa Lucía Cloud Forest Reserve, trail to waterfalls, 0.109450°N, -78.609380°W (DD), 1645 m, collected on 12 September 2013 by D. Ortiz and O. Torres-Carvajal; QCAZ 11927–29, Nanegal, Santa Lucía Cloud Forest Reserve, 0.113330°N, -78.613280°W (DD), 1736 m, collected on 6 November 2013 by F. Ayala-Varela, E. Carrillo, V. Macias and T. Ostos; QCAZ 10666, 10753, same collection data as holotype, but collected on 14 July 2010 by V. Aguirre-Peñafiel and 26 July 2010 by S. Maddock and V. Aguirre-Peñafiel, respectively. QCAZ 10671, Nanegal, Santa Lucía Cloud Forest Reserve, 0.119280°N, -78.596470°W (DD), 1911 m, collected on 29 June 2010 by M.A. Chinchero.

Alopoglossus viridiceps can be distinguished from all other known congeners except Alopoglossus festae by having a double longitudinal row of widened gular scales and lanceolate dorsal scales in transverse rows. From Alopoglossus festae (character states in parentheses, taken from Köhler et al. 2012), the new species differs in having 29–32 dorsal scales in a transverse row at midbody (16–24, mean = 19.14 ± 2.25), four ventral scales in a transverse row at midbody (six), and a distinct longitudinal light stripe from mouth commissure to shoulder (Fig. 3). Scale counts and measurements of Alopoglossus festae and Alopoglossus viridiceps are presented in Table 2.

Male (Figs 1, 2); SVL= 57.89; TL/SVL= 1.99; HL/SVL = 0.24; HW/SVL = 0.16; ShL/SVL = 0.16; AGD/SVL = 0.43; ANS/HL = 3.58.

Rostral hexagonal, 2.08 times as wide as high, visible from above, in broad contact with frontonasal. Frontonasal irregularly pentagonal, wider than long, laterally in contact with nasal. Prefrontals irregularly pentagonal, nearly as wide as long, with medial suture; laterally in contact with nasal, loreal, and first and second supraocular. Frontal irregularly hexagonal, nearly twice as long as wide, slightly wider anteriorly; at each side in contact with supraoculars II–III. Frontoparietals irregularly pentagonal, longer than wide, with a wide medial suture; each in contact with supraoculars III–IV. Interparietal pentagonal, lateral borders parallel to each other. A pair of irregularly hexagonal parietals, approximately as wide and as long as interparietal. Interparietal and parietals forming slightly undulating posterior head margin. Occipitals absent. Four supraoculars, first one smallest and second one largest. Four elongate superciliaries, first one widest, followed by a postsuperciliary scale, which is also in contact with supraocular IV and anterior supratemporal. Nasal divided, irregularly pentagonal, longer than wide, in contact with rostral anteriorly, first and second supralabials ventrally, frontonasal and prefrontals dorsally, loreal posterodorsally, and frenocular posteroventrally. Nostril in lower part of nasal, directed lateroposteriorly. Loreal small, quadrangular. Frenocular in contact with nasal, separating loreal from supralabials. Three suboculars, the one below eye very elongated (nearly three times the size of adjacent suboculars). Posterior subocular continuous with three postoculars. Semitransparent disc in lower eyelid with vertical sections delimiting six large scales on right side and five scales on left side. Five supralabials, third one longest and below center of eye. Two postsupralabials. Temporals small, irregularly polygonal, juxtaposed, keeled. Two large supratemporal scales, posterior one keeled. Ear opening vertically oval, without denticulate margins. Tympanum recessed into a short auditory meatus. All dorsal and lateral head scales juxtaposed. Interparietal and parietals with lateral ridges, other dorsal head scales smooth. Mental trapezoidal, anterior margin nearly forming a semicircle. Postmental irregularly heptagonal, wider than long. Four infralabials, third one longest and below center of eye. One postinfralabial. Three pairs of chin shields, first two in contact medially and with infralabials; third one in contact medially but separated from infralabials. Third pair of chin shields separated from gulars by two transverse rows of scales. Anterior row composed laterally by two scales (one on each side) similar in size to the scales on the posterior row, and medially by two enlarged scales (not in contact medially) similar in size to the enlarged gulars. Gulars imbricate, smooth, in four longitudinal rows, the medial double row formed by five pairs of distinctly widened scales. Posterior row (collar) with five scales, the medial three distinctly widened (Fig. 2).

Scales on nape similar to dorsals, except that anterior ones are shorter. Scales on sides of neck small, keeled and mostly granular. Dorsals and scales on flanks lanceolate, strongly keeled and mucronate, imbricate, in transverse rows; number of scales along a middorsal line from nape to base of tail 30; transversal dorsal count 31. Ventrals smooth, imbricate, with round posterior margin; 18 in a longitudinal count; four in a transverse count. Scales on flanks similar to dorsals. One femoral pore on each side, in preanal position, separated from each other by four ventral scales. Scales on tail keeled, slightly mucronate, imbricate; in transverse and longitudinal rows; dorsal keels sharp, forming four distinct longitudinal ridges. Scales on limbs mostly rhomboidal, imbricate, sharply keeled, and mucronate; smooth on ventral aspect of hind limbs, small and keeled or tuberculate on ventral aspect of upper arms and posterior aspect of thighs. Subdigital lamellae of fingers and toes single, transversely enlarged and smooth; 20 under fourth toe.

(Fig. 1). Dorsal background uniformly dark brown with a wide light brown vertebral stripe extending from occiput onto tail; vertebral stripe wider anteriorly; dorsal surface of head bright metallic green medially (rostral, frontonasal, prefrontals, frontal and frontoparietals) and dark brown laterally (supraoculars and supratemporals), with a lateral bright green stripe on each side extending posteriorly from the border between the loreal and the first supraocular, over the superciliaries, to the lateral border of the parietal; lateral aspect of neck with a longitudinal yellowish-green stripe extending posteriorly from mouth commissure, over ventral margin of tympanum, to shoulder; most scales between lateral neck stripe and gular region reddish brown forming a short irregular stripe between last infralabial and shoulder; ventral surface of head light green, brighter laterally; gular and pectoral regions same tone as chin shields but lighter; ventral aspect of body orange with scattered light green or light blue small marks; ventral aspect of tail with dark brown marks that form transverse bars on the posterior half.

Intraspecific variation in scale counts and measurements in Alopoglossus viridiceps sp. n. is presented in Table 2. Color in preservative of holotype is similar to its color in life, except that the bright green tones of the head and orange tones of the venter have faded away.

Color in life of juvenile paratypes QCAZ10671, QCAZ11854–55 is similar to that of the holotype except that these juveniles have a reddish-brown longitudinal stripe extending from the dorsal border of the tympanum to the shoulder and fading away on the flanks (Fig. 3). The orange ventral coloration of male juvenile QCAZ11854 does not extend onto tail as in the holotype; female juvenile QCAZ10671 and juvenile QCAZ11855 (undetermined sex) have a light yellowish green background color on the venter, similar to that on gular region and chin (Fig. 3).

Alopoglossus viridiceps sp. n. inhabits cloud forests on the Pacific slopes of the Andes in northwestern Ecuador (Fig. 4). It occurs at elevations of 1246–1911 m in the province of Pichincha. Most type specimens were collected at Santa Lucía Cloud Forest Reserve, which extends between 1400–2560 m and has an area of 756 ha; annual precipitation ranges from 1500 to 2800 mm, and average annual temperature is recorded at 16 °C (Rivas-Martínez and Navarro 1995). Specimens of Alopoglossus viridiceps sp. n. were found active between 9h30–11h30 on leaf litter in primary forest, or on the border of sugar cane plantations. Other species of small ground lizards collected in the same area include the sphaerodactylid gecko Lepidoblepharis conolepis, the gymnophthalmids Cercosaura vertebralis and Echinosaura brachycephala, as well as an undescribed species of the gymnophthalmid genus Riama.

The specific epithet viridiceps is an adjective derived from the Latin words “viridis” and “ceps”, which mean “green” and “head”, respectively. It refers to the distinctive bright green coloration of the dorsal and ventral aspects of the head of Alopoglossus viridiceps sp. n.

Of the 596 nucleotide characters included in our analysis 290 were constant, 70 parsimony uninformative, and 236 were parsimony informative. Selected models of evolution were 012013+I+G+F, TPM2uf+I+G, and 010220+I+G+F for ND4 partitions codon 1, 2, and 3, respectively. The resulting 50% majority rule consensus tree (Fig. 5) supports strongly (PP=1) the monophyly of Alopoglossinae (i.e., Ptychoglossus and Alopoglossus) and Alopoglossus. Within Alopoglossus there is a basal split into two strongly supported (PP=1) clades, one containing trans-Andean taxa (Alopoglossus festae and Alopoglossus viridiceps sp. n.), and the other including cis-Andean taxa (Alopoglossus angulatus, Alopoglossus atriventris, Alopoglossus buckleyi, and Alopoglossus copii). Within the cis-Andean clade, Alopoglossus angulatus and Alopoglossus copii are recovered as sister species with maximum support (PP=1), forming a clade sister to Alopoglossus atriventris (PP=0.84); Alopoglossus buckleyi is sister to all other cis-Andean species (Fig. 5).

Uncorrected genetic distances for ND4 are presented in Table 3. Distance values between Ptychoglossus brevifrontalis and species of Alopoglossus ranged between 0.197–0.225. The genetic distance between Alopoglossus viridiceps sp. n. and its sister species Alopoglossus festae (0.124) is slightly lower than all other interspecific distance values within Alopoglossus (0.148–0.185). Alopoglossus angulatus, the only species for which we had two samples, had an intraspecific distance value of 0.06.