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Higher TaxaTropiduridae, Iguania, Sauria, Squamata (lizards)
Common Names 
DistributionPeru (Amazonas)

Type locality: Amazonas Department, Bongará Province, Cuispes District, Cuispes village; from farms adjacent to Cuispes village, 5°55.49’S, 77°56.94’W; 1850 m a.s.l.  
TypesHolotype: CORBIDI 18658, adult male; 7 Mar. 2017; G. Chávez leg. Paratypes: CORBIDI 18659–61; 2 adult males, 1 female juvenile; collected with the holotype; Amazonas Department, Bongará Province, Shipasbamba District, Canta Gallo; 5°55.43’S, 77°59.03’W; 1720 m a.s.l.; 27 Aug. 2017; A. García-Bravo leg.; CORBIDI 18748, 18749, 18750; CORBIDI 22035, 1 female, adult; Amazonas Department, Bongará Province, Cuispes District, Cuispes village; 5°55.79’S, 77°56.66’W; 1880 m a.s.l.; 25 Sept. 2019; L.A. García-Ayachi leg. 
DiagnosisDiagnosis. Stenocercus flagracanthus sp. nov. differs from all other species of Stenocercus, except from S. arndti Venegas, Echevarria & Alvarez, 2014, S. bolivarensis Castro & Ayala, 1982, S. carrioni Parker, 1934, S. chlorostictus Cadle, 1991, S. crassicaudatus Tschudi, 1845, S. empetrus Fritts, 1972, S. eunetopsis Cadle, 1991, S. torquatus Boulenger, 1885, and S. simonsii Boulenger, 1899 by having granular scales on the posterior surface of the thighs, a relatively short tail, caudals spinose and two caudal whorls per autotomic segment. Among the aforementioned species, S. flagracanthus sp. nov., possesses caudal scales with the most strongly projected mucrons. This difference is evident comparing S. flagracanthus sp. nov. with S. carrioni, S. crassicaudatus, S. empetrus, S. eunetopsis, and S. simonsii, and to a lesser degree comparing it with S. arndti, S. chlorostictus and S. torquatus. Moreover, the size of mucrons along the second half of the tail in S. flagracanthus sp. nov., is clearly alternating, with large mucrons followed by small mucrons per each caudal whorl. In the other species, this character is indistinct or only possible to observe at the distal extreme, like in S. carrioni. With the goal of facilitating the distinction between S. flagracanthus sp. nov. and the aforementioned species, herein, we provide more differences.
Stenocercus flagracanthus sp. nov. differs from S. carrioni, S. chlorostictus and S. euneptopsis by having dorsal scales of the neck granular and not keeled (keeled and imbricate in the three former species). Stenocercus flagracanthus sp. nov. can be easily distinguished from S. crassicaudatus and S. empetrus by having a distinct black antehumeral collar (faint or absent in the remaining species). Stenocercus crassicaudatus, S. euneptopsis and S. simonsii have longer tails than S. flagracanthus sp. nov. with 57 to 62%, 64 to 66%, and 57 to 63% versus 50 to 54% of total length, respectively. Stenocercus flagracanthus sp. nov. also differs from S. crassicaudatus by having fewer scales around midbody with 96 to 104 (xˉ = 99.63) in the new species, and 97 to 121 (xˉ = 108.87) in S. crassicaudatus. Stenocercus flagracanthus sp. nov. differs from S. bolivarensis by having granular lateral body scales versus strongly keeled and imbricate lateral body scales (Torres-Carvajal 2007b).
Males of S. arndti are easily distinguished from S. flagracanthus sp. nov. by having a bold black transverse band at midbody that extends ventrolaterally (absent in S. flagracanthus sp. nov.). Stenocercus torquatus can be distinguished from S. flagracanthus sp. nov. by having black nuchal bands, absent in S. flagracanthus sp. nov. Moreover, Stenocercus torquatus has more scales around midbody than S. flagracanthus sp. nov. (120 to 137, xˉ = 116.96 versus96to104,xˉ=99.63,respectively).Stenocercus empetrus can be easily separated from S. flagracanthus sp. nov. by the ventral coloration, venter yellowish-orange with black reticulations in the former and whitish gray without reticulations in S. flagracanthus sp. nov. Stenocercus roseiventris D’Orbigny in Duméril & Bibron, 1837 and S. marmoratus Duméril & Bibron, 1837 share with S. flagracanthus sp. nov. the presence of caudal scales with strongly projected mucrons but differ by having the scales on the dorsal surface of neck and posterior surface of thighs imbricate and keeled. (Venegas et al. 2020)

Definition. (1) Maximum SVL in males 76.8 mm (n = 5); (2) maximum SVL in females 68.3 mm (n = 1); (3) vertebrals 83–97; (4) paravertebrals 95–111; (5) scales around midbody 96–104 (6) supraoculars 4–6; (7) internasals 4–6; (8) postrostrals 4–5; (9) loreals 4–7; (10) gulars 55–62; (11) lamellae on Finger IV 26–29; (12) lamellae on Toe IV 30–33; (13) posthumeral mite pocket present as one or more vertical folds or ridges [Type 1 of Torres-Carvajal (2007b)]; (14) postfemoral mite pocket distinct with slit-like opening [Type 2 of Torres-Carvajal (2007b)]; (15) parietal eye absent; (16) occipital scales small, smooth, juxtaposed; (17) projecting angulate temporal absent; (18) row of enlarged supraoculars occupying most of supraocular region absent; (19) scales on frontonasal region juxtaposed, smooth; (20) preauricular fringe short; (21) antegular, antehumeral, gular, longitudinal, oblique, postauricular, and supra-auricular neck folds present; (22) lateral nuchals and dorsals similar in size; (23) lateral body scales, granular, smaller than dorsals, becoming slightly imbricate toward the groin; (24) vertebrals slightly enlarged, forming a distinct row of scales from forelimbs to hindlimbs; (25) dorsolateral crest absent; (26) paravertebrals from the second third of dorsum, like the adjacent dorsals, becoming gradually larger, imbricate, keeled and mucronate toward the hindlimb insertion; (27) ventral scales smooth, imbricate; (28) scales on posterior surface of thighs granular; (29) prefemoral fold present; (30) inguinal groove present; (31) preanals not projected; (32) tail not compressed laterally; (33) tail relatively short (tail length 50–54% of total length); (34) caudal whorls per autotomic segment two; (35) tail strongly spinose; (36) postocular stripe present; (37) gular region in males grayish with cream dots; (38) gular region in females grayish with pale dots; (39) black patch on ventral surface of neck in adult males absent; (40) dark midventral stripe in adult males absent; (41) dark patch on ventral surface of thighs, vent and tail in adult males absent; (42) background color of dorsum pale brown in males and gray in females, but with distinct black transversal stripes in both sexes; (43) two post-xiphisternal pairs of inscriptional ribs, one long (not in contact midventrally) and the other short (Pattern 1B of Torres-Carvajal 2004). (Venegas et al. 2020)

Description of holotype. Male (Fig. 10); SVL 75.0 mm; TL 87.0 mm; maximum head width 16.0 mm; head length 19.0 mm; head height 12.4 mm; scales on parietal and occipital regions small, smooth, juxtaposed, subequal in size; parietal eye not visible: supraoculars smooth, juxtaposed; circumorbitals absent; canthals two; loreals six; postrostrals four; internasals five; supralabials five; infralabials five; lorilabials in one row; preocular divided into two scales, most dorsal in contact with posterior canthal; lateral temporals granular; gulars in 56 rows between tympanic openings; all gulars cycloid, smooth, imbricated; second infralabial in contact with first and second sublabials; first pair of postmentals in contact; mental in contact with first pair of infralabials and first pair of postmentals; dorsal and lateral scales of neck granular until the level of arm insertion, becoming gradually enlarged, imbricate, keeled to strongly keeled, and mucronate toward the hindlimbs insertion; lateral scales of body granular becoming slightly imbricate and feebly keeled toward the groin; scales around midbody 101; vertebrals 97 enlarged, keeled on the second half of body, imbricate, forming indistinct vertebral row; paravertebrals adjacent to vertebrals row larger than dorsals, keeled, imbricate becoming larger and mucronate toward hindlimb insertion; paravertebrals 111; ventrals smooth, imbricate, nearly twice the size of the dorsals, only paravertebrals near hindlimb insertion are twice the size of ventrals; preauricular fringe short composed of five enlarged, granular scales; suprauricular, antehumeral, gular, longitudinal, oblique, antegular, postauricular and rictal neck folds present; dorsolateral, ventrolateral and prefemoral folds present; dorsal scales of forelimbs imbricate, feebly keeled; dorsal scales of hindlimbs imbricate, strongly keeled and mucronate; ventral humeral scales granular becoming imbricate toward to the forearm; ventral scales of forelimbs and hindlimbs smooth, imbricate; palmar and plantar scales imbricate, keeled; lamellae on Finger IV 29; lamellae on Toe IV 33; tail rounded (tail length 53% of total length); caudal scales keeled, strongly mucronate, imbricate; basal subcaudal scales smooth, imbricate; posthumeral mite pocket present as one or more vertical folds or ridges; postfemoral mite pocket distinct with slit-like opening. (Venegas et al. 2020)

Coloration in life (Fig. 11A, B). Dorsal surface pale brown spattered with dirty cream dots bearing a distinct black collar (incomplete dorsally) with dirty cream borders, broad black stripes without pale interspaces along dorsum, finely blotched with black on neck and limbs, and a middorsal triangular black blotch posterior to occiput; dorsal surface of head with black flecks; side of head with the loreal region, subocular scale, and jaws gray, supralabials and temporal region pale brown with a postocular black stripe; tail black with the distal quarter brown. Ventral surface creamy gray with the gular region gray with faint cream blotches better defined on the sides; tail surface at the distal half gray. Iris pale brown.
Coloration in preservative (Fig. 10D, E). Dorsal coloration gray, except on the head that remains brown, dots whitish cream, the borders of the collar white, and the black marks as in life. Ventral surface whitish cream with the gular region darker than in life. (Venegas et al. 2020)

Intraspecific variation. Measurements, scutellation, and other morphological characters of Stenocercus flagracanthus sp. nov. are presented in Table 2. Loreals 4–7; supralabials 4–6; infralabials 5; second infralabials in contact with third sublabials in 75% of specimens; first pair of postmentals in contact medially in all specimens. In one dissected paratype the pattern was two xiphisternal and two postxiphisternal pairs of inscriptional ribs, one long but not in contact midventrally and the other short [Pattern 1B; Torres-Carvajal (2004)].
The adult male paratypes (n = 4) are identical to the holotype (Fig. 11). Sexual dimorphism is noticeable in size, the single collected female (CORBIDI 18661) is smaller than males (Table 2). The black collar can be complete or incomplete and is present in both sexes, gray in the single female paratype and black in males. The dorsum in the female paratype is grayish brown; the dorsal black marks along the back of males are faint gray and black on the pelvic region and tail (Fig. 11E, F). The single juvenile specimen has the dorsum gray including the tail with a well-defined complete dark gray collar but without the transverse black stripes of the adult individuals and dorsal surface of head brown. (Venegas et al. 2020)

Comparisons: For a comparison of scutellation across S. aculeatus, S. angulifer, S. catherineae, S. dracopennatus, S. huancabambae, and S. philmayi see Venegas et al. 2020. 
EtymologyNamed after the Latin words “flagrum” (= whip, derived from “flagellum”) and the Greek “acanthos” (= spine or thorn). It refers to the spiny tail of this new species of lizard that resembles the ancient Roman torture tool, the “flagrum”, a whip-like instrument with accessories for inflicting damage. The specific epithet “flagracanthus” is a noun in apposition. 
  • Venegas PJ, García-Ayachi LA, Chávez-Arribasplata JC, Chávez G, Wong I, García-Bravo A 2020. Four new species of Stenocercus Duméril & Bibron, 1837 (Squamata, Iguania) from the Department of Amazonas in northeastern Peru. Evolutionary Systematics 4(2): 79-108 - get paper here
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