Plestiodon nietoi, Feria-Ortiz, Manuel & García-Vázquez, Uri Omar, 2012

Plestiodon nietoi sp. nov.

( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 )

Holotype. MZFC 22249 (original number JCBH 115), an adult male, collected by Jean Cristian Blancas Hernandez on 0 5 February 2007 from La Llave, El Balcón, Ajuchitan del Progreso, Guerrero, México (17° 37’ 21.9’’ N, 100° 34’ 29.3’’ W) at 1831 m.

Paratypes. Twelve specimens, all from Ajuchitlan del Progreso municipality, Guerrero, Mexico: three from the same locality as the holotype ( MZFC 22250–22252); two from El Filo, El Balcón ( MZFC 22247–22248); two from El Moreno, El Balcón ( MZFC 22253–22254); and five from road La Ola-San Antonio Texas (UTA-R 58460- 58464).

Diagnosis. Plestiodon nietoi sp. nov. can be distinguished from all other species of the P. brevirostris group by large adult body size (up to 77 mm maximum SVL in P. n i e t o i sp. nov. vs. 73 mm maximum SVL in the other species; Table 1). In addition, P. nietoi sp. nov. can be distinguished from P. ochoterenae , P. parviauriculatus , P. c o p e i, P. brevirostris , and P. d i c e i by having the interparietal enclosed posteriorly by parietals in most specimens (91.7% in P. nietoi sp. nov., 0–11.8% in all other taxa), and from P. bilineatus , P. dicei and P. indubitus by having a pale lateral line on the neck (absent in the other subspecies and replaced by a series of scales that have white anterior edges and centers with black posterior borders, on longitudinal scale rows 5–9 or any combination of these rows in sequence on P. indubitus ). Plestiodon nietoi sp. nov. can be distinguished from P. dugesii by having four supraoculars (vs. three in P. dugesii ).

Furthermore, P. nietoi sp. nov. differs from P. parvulus and P. copei by having the seventh supralabial in contact with the upper secondary temporal (absence of contact in P. parvulus and P. c o p e i), from P. colimensis by having fewer scales encircling the body (21–23, x = 22.1, n = 13 in P. n i e t o i; 27–28, x = 27.5, n = 2 in P. c o l i m e n s i s) and more body scales than P. parviauriculatus (19–20, x = 19.9, n = 14). Additionally, P. n i e t o i sp. nov. may be distinguished from P. brevirostris , P. dicei , and P. copei by fewer paravertebral scales (47–51, x = 50, n = 13 in P. n i e - toi sp. nov., 52–58, x = 56.0, n = 38; 48–60, x = 55.3, n = 46; and 53–61, x = 56.6, n = 35, in P. brevirostris , P. dicei , and P. copei , respectively).

Description of the holotype. The undissected holotype is an adult male with partially everted hemipenes. SVL = 71.97 mm; snout to eye 5.24 mm; snout to base of forearm 23.83 mm; trunk length from axilla to groin 40.47 mm; greatest head width (between angles of jaws) 6.66 mm; head length (tip of snout to posterior margin of ear) 14.73 mm; greatest body width 9.29 mm. Tail regenerated, 16.13 mm in length. Limbs pentadactyl, fore- and hindlimbs separated by one scale when adpressed; straightened limbs measuring (from insertion to tip of longest digit) 18.07 mm forelimb (25% SVL), 24.63 mm hind limb (34% SVL). Outer posterior tubercle of wrist enlarged.

Snout rounded in dorsal and lateral view; rostral more than twice as wide as high, in broad contact with supranasals posteriorly. Supranasals wider than long, in broad contact with each other and each with nasal. Frontonasal more than twice as wide as long, posterior margin straight, in contact with prefrontals posteriorly. Prefrontals in contact, about as wide as long, posterior margins rounded, in contact with first supraocular, anterior and posterior loreals, and first superciliary. Frontal large, elongate, slightly triangular (2.36 mm x 3.97 mm), in contact with prefrontals, first two and three supraoculars on left and right side, respectively, and frontoparietals. Frontoparietals contact each other and each one contacts frontal anteriorly, third and fourth supraoculars laterally, and parietal and interparietal posteriorly. Four supraoculars. First supraocular smaller than other three, in contact with frontal, prefrontal, and first and second superciliaries. Second supraocular nearly same size as third, in contact with frontal at its medial margen, and with second and third superciliaries at its medial side. Third supraocular in contact with both frontoparietal and frontal, and third and fourth superciliaries. Fourth supraocular smaller than second and third, and in contact with frontoparietal, parietal, and fourth and fifth superciliaries. Interparietal small (2.95 mm x 2.05 mm), slightly elongate, triangular, enclosed by frontoparietals and parietals; no pineal foramen visible. Parietals large, elongate, obliquely oriented, in narrow contact with each other posterior to interparietal; contact with fifth superciliary and upper postsubocular, and upper secondary temporal laterally; in posterior contact with first nuchal. Four large nuchals on right side and three on left side; those of first pair approximately twice as wide as long; those of second, third pairs and fourth nuchals on right side approximately 2.5−3.0 times as wide as long; first, second, and third pair in medial contact with each other. First nuchals in contact with parietals, upper secondary temporal and tertiary temporal.

Nasals longer than high, nostril centrally situated; each nasal in contact with rostral and supranasal. Two loreals on each side of head; in both the anterior loreal contacts first and second supralabials, is higher than wide; posterior loreal approximately twice as wide as high, notably wider than anterior loreal, in contact with prefrontal, first superciliary, preocular, and second, third, and fourth supraoculars. One small preocular on either side. Superciliaries 5/5; first superciliary largest, in contact with first supraocular, prefrontal, posterior loreal, and first upper palpebral; second superciliary more elongate than the others; second, third, and fourth scales in superciliary series gradually becoming shorter and lower posteriorly; fourth and fifth superciliaries longer and higher than third, respectively. Upper palpebrals 7/7; lower palpebrals 10/10; lower eyelid movable; no transparent window in lower eyelid. Five scales of lower eyelid on the right side, vertically elongate, rectangular, and diminishing in size from the center, in contact with lower palpebral scales. Eight scales of lower eyelid on left side, vertically elongate, rectangular, and diminishing in size from the center. Two postoculars on either side. Subocular row incomplete, separated by fifth supralabial below center of eye. Presuboculars 2/2. Anterior presubocular in contact with fourth supralabial; posterior presubocular in contact with fourth and fifth supralabials (in both sides). Postsuboculars 3/3. First postsubocular in contact with sixth and fifth supralabials (on both sides). Second postsubocular in contact with primary temporal, and sixth supralabial; third postsuboluclar larger than other two, and in contact with parietal, upper secondary temporal, and primary temporal on both sides. Primary temporal 1/1. Lower secondary temporal vertically elongate, approximately three times the size of primary temporal, smaller than upper secondary temporal, and separated from primary temporal by contact of upper secondary temporal and seventh supralabial; tertiary temporal large, approximately twice as high as wide. Seven supralabials on each side. Second and third supralabials of similar size and slightly shorter than first. Sixth supralabial smaller than seventh, and larger than other five supralabials. Seventh supralabial largest. Two postlabials on each side.

Seven infralabials on each side; mental slightly more than twice as wide as long; postmental slightly longer than mental, in contact with first two infralabials on each side; three pairs of enlarged chinshields, with first pair in broad contact, second pair separated by one scale; third pair separated by three scales. The scale that medially borders the postgenial is wider than long.

External ear opening rounded and smaller than eye opening, without lobules or spines. Scales smooth to slightly striated, in 24 rows around neck just anterior to forearm; in 22 rows around midbody; in 13 rows around base of tail. Dorsals in 50 transverse rows (from end of nuchals to level above vent), nearly equal in size to ventrals. Scales of limbs smooth and slightly striated as on body. Supradigital scales in one row; subdigital lamellae rounded. Digits short, subdigital counts follow s Myers & Donnelly (1991): hand: I 5 /5 II 8 / 8 III 10 / 10 IV 10 / 10 V 7 /7 (fingers II, III, and IV broken); foot: I 5 /5 II 8 /? III 10 /? IV 13 /? V 9 /9

Median enlarged preanal scales nearly twice as large as adjacent ventrals, overlapped by outer smaller preanals. Subcaudals widened beginning on third row posterior vent; subcaudals nearly as large as ventrals on other rows; subcaudals widened on regenerated portion of tail.

Color pattern in preservative. Olive brown dorsally, dark brown laterally and light grey ventrally. Dorsolateral light line begins on rostral, passes posteriorly along lower half of supranasal, the lower one-third of frontonasal and upper edge of anterior loreal, the lower one-third of prefrontal and the upper edge of the posterior loreal, and the lower side of the supraoculars; passes along the upper portion of the lower half of the three (four on the right side) nuchals; at level of neck, the light dorsolateral line initially passes along the second scale row and includes more of the lower half of each scale; on the fourth dorsal scale at level of neck, the line comprises almost the entire second scale row and the upper edge of the third scale row, slightly widening to the 20th scale, diminishing and becoming more diffuse posteriorly; at midbody, it comprises the lower edge of the third and upper third of the fourth scale row, and disappears further at midbody. Dorsal scales dark brown with light edges, including dorsal scales of tail.

Lateral light line begins on rostral and terminates at fourth (seventh on left side) scale anterior to forelimb, passing on lower edge of the first four supralabials, and ascending to upper half of fifth scale (on both sides), on the sixth and seventh supralabials; the line is fine, continuous, and approximately passes through the middle of these scales on both sides; at level of neck, it comprises the upper portion of the seventh and lower portion of the sixth scale rows (on both sides).

Upper secondary dark line begins on rostral and terminates at fifth scale anterior to forelimbs; primary lateral stripe begins next to rostral; comprises the lateral side of head. At the level of neck it reaches the third row in the upper part of scales and the upper half of the sixth row of the scales on its lower part; at midbody, lateral scales have light edges causing the dark band to appear diffuse. Ventral area of limbs brownish gray, dorsal area dark brown.

Variation. Variation in meristic characters of the type series (n=13;including holotype) as follows: superciliaries on left side 5–7 (5, 2 including holotype; 6, 4; 7, 7), x = 6.4; superciliaries on right side 5–7 (5, 2 including holotype; 6, 6; 7, 5), x = 6.2; postsuboculars on left side 3–4 (3, 9 including holotype; 4, 4), x = 3.3; postsuboculars on right side 3–4 (3, 10 including holotype; 4, 3), x = 3.2; supraoculars 4/ 4 in all specimens, except MZFC 22250 (3/3).

Sixth supralabial in contact with two or three postsuboculars on left side (2, 9 including holotype; 3, 4), x = 2.3; also with two or three on right side (2, 10 including holotype; 3, 3), x =2.2; upper postlabials in contact with one scale (of similar size or larger than the one) in MZFC 22252 and UTA-R 58462; with 1–2 in MZFC 22254; with 2 in the rest of the specimens (including holotype), except MZFC 22247 where postlabial is fused with tertiary temporal; 1 postlabial in MZFC 22253 and UTA-R 58462; 1/ 2 in MZFC 22254; 2 in the rest of the specimens (including holotype). Number of scales that contact both nuchal and upper postlabial 1–2 (1, 7; 2, 6 including holotype) x = 1.5; paravertebral scales 47–51 (47, 1; 49, 1 holotype, 50, 7; 51, 4), x = 50; dorsal rows 21–23 (21, 2including holotype; 22, 8; 23, 3), x = 22; lamellae under fourth toe 13–15 (13, 3 including holotype; 14, 3; 15, 7), x = 14.3.

Etymology. The specific epithet is a patronym honoring Adrian Nieto Montes de Oca for his research on the herpetofauna of México, specifically with taxa from the families Polychrotidae , Teiidae , and Scincidae .

Distribution and habitat. Plestiodon nietoi sp. nov. is known only from two localities in Sierra Madre del Sur, Guerrero ( Fig. 3 View FIGURE 3 ), at 1831–2259 m. All specimens from each locality were collected the same day (5 February 2007 from El Balcón and 6 June 2007 from Road la Ola-San Antonio Texas). The first specimen was found at 0 930 h and the last at 1600 h. All specimens were collected while inactive beneath pine logs within oak and pine forest ( Fig. 4 View FIGURE 4 ).

The vegetation at the type locality is composed of oak forest ( Quercus candicans , Q. elliptica , Q. crassifolia , Q. urbanii , and Pinus devoniana ), pine-oak forest ( Pinus montezumae , P. pringlei , P. douglasiana , P. oocarpa var. trifoliata , Quercus candicans , Q. scytophylla , Q. crassifolia , Q. castanea , Q. elliptica , and Q. urvanii ), and rain forest (Persea americana, Pinus chiapensis , Quercus uxoris , Q. rubramenta , Pinus ayacahuite , Clethra sp., Abies sp., Carpinus caroliniana , Billia hippocastanumm , and Cojoba arborea ). The climate is temperate (mean annual temperature = 17 ºC; mean temperature of the coldest and warmest months 16.2 ºC and 18.1 ºC, respectively), with annual seasonal precipitation averaging less than 1698.4 mm (Blancas et al. 2007).

Comparisons to other species. According to Robinson (1979) the skinks of the Plestiodon brevirostris group differ from others Plestiodon groups by the shape of the scale that medially borders the postgenial. It is wider than long in the members of the brevirostris group and longer than wide in others groups of Plestiodon . In P. nietoi sp. nov., this scale is wider than long. In addition, P. n ie t oi sp. nov. has another character which also is shared by most of the brevirostris group members ( Dixon 1969) in that the seventh supralabial contacts with the upper secondary temporal. This character is found only within the brevirostris group. Thus, the presence of these characters in P. nietoi sp. nov. clearly places this species within the brevirostris group.

Plestiodon nietoi sp. nov. shares some characters with others species of the brevirostris group. For example, the mean number of longitudinal scale rows is similar to P. c o p e i and P. nietoi sp. nov. (Table 1). However, all species of the group, except P. brevirostris , have diagnostic characteristics that distinguish them from P. n i e t o i sp. nov.; for each of the different species of P. brevirostris group (except P. dugesii ) at least one character is present in all individuals of each species that differs from P. nietoi sp. nov. (Table 1). Although P. n i e t o i sp. nov. is phenotypically similar to P. dugesii , the later species is the only one in the brevirostris group to possess three supraocular scales ( Dixon 1969).

The morphology and the distribution also indicate that the species P. dicei and P. bilineatus are different from P. nietoi sp. nov. The first species is distributed in the northern region of the Sierra Madre Oriental and is isolated from the populations of El Balcón and the Ola by more than 630 km. Likewise, P. bilineatus is found in the northern region from the Sierra Madre Occidental, approximately 1000 km from the populations of El Balcón and the Ola. Likewise, P. nietoi can be distinguished from these two species by the presence of the lateral light line on the neck, absent in P. dicei , and found in a low frequency in P. bilineatus (Table 1).

Plestiodon nietoi sp. nov. shares several characters with P. brevirostris and P. indubitus . These three taxa possess a primary temporal, a number of longitudinal scale rows and the seventh supralabial is in contact with the upper secondary temporal (Table 1). However, P. nietoi sp. nov. can be differentiated from the two species in that this species possesses both a lateral light line on the neck and interparietal enclosed posteriorly by the parietals. Plestiodon brevirostris also possesses a lateral light line on the neck but is different from P. nietoi sp. nov. in that the parietals do not enclose the interparietal posteriorly. Similarly, the posterior contact of the parietals (which enclose the interparietal scale) is shared for several taxa of the brevirostris group (P. c o li m e ns i s, P. parvulus , P. bilineatus , P. indubitus , and P. nietoi sp. nov.). Nevertheless, both distribution and morphology suggest that each species is different from P. nietoi sp. nov. Plestiodon indubitus is similar to P. nietoi in the presence of posterior contact between the parietals, but can be differentiated from P. nietoi sp. nov. by the form of the lateral light line on the neck. In P. indubitus , the lateral light line is replaced by a series of scales that have white anterior edges and centers with black posterior borders, on longitudinal scale rows 5–9, or any combination of these rows in sequence. The joint presence of lateral light lines and of interparietal enclosed by parietals in 12 of 13 specimens examined for P. n i e t o i sp. nov. indicate that the frequency of this condition in P. n i e t o i sp. nov. is relatively high. By contrast, the frequency of this condition is very low in P. brevirostris and P. indubitus (5.2 and 2%, respectively).

Plestiodon nietoi sp. nov. also differ of P. brevirostris and P. indubitus in the mean body size, the mean number of lamellae on the fourth toe, and the number of transverse scale rows (Table 1). Although there is overlap in the ranges of variation of these characters the differences are large and support the notion that P. nietoi sp. nov. is a distinct species. The body size shows a wide overlap between P. nietoi sp. nov. and P. indubitus or P. brevirostris . However, is it significant that the next largest specimen of P. ni e to i sp. nov. (74 mm) is also larger than the maximum size of P. brevirostris or P. indubitus (either reported by Dixon (1969), or recorded in this study), and the next two largest specimens are also larger than the maximum size of P. brevirostris or P. indubitus found in this study (despite the relatively large sample sizes of those subspecies).