Brachymeles ligtas, Geheber, Aaron D., Davis, Drew R., Watters, Jessa L., Penrod, Michelle L., Feller, Kathryn D., Davey, Conner S., Ellsworth, Elyse D., Flanagan, Rachel L., Heitz, Brendan B., Moore, Tana, Nguyen, Marie D. C., Roberts, Austyn, Sutton, John, Sanguila, Marites B., Linkem, Charles W., Brown, Rafe M. & Siler, Cameron D., 2016

Geheber, Aaron D., Davis, Drew R., Watters, Jessa L., Penrod, Michelle L., Feller, Kathryn D., Davey, Conner S., Ellsworth, Elyse D., Flanagan, Rachel L., Heitz, Brendan B., Moore, Tana, Nguyen, Marie D. C., Roberts, Austyn, Sutton, John, Sanguila, Marites B., Linkem, Charles W., Brown, Rafe M. & Siler, Cameron D., 2016, Additions to Philippine Slender Skinks of the Brachymeles bonitae Complex (Reptilia: Squamata: Scincidae) I: a new species from Lubang Island, Zootaxa 4132 (1), pp. 1-14 : 4-8

Brachymeles ligtas sp. nov.

( Figs. 2 , 3 )

Brachymeles bonitae Duméril & Bibron 1839 ; Taylor 1917; Brown 1956:5; Brown & Rabor 1967:526; Brown & Alcala 1970; Brown & Alcala 1980:20; Davis et al. 2014.

Holotype. PNM 9818 ( CDS Field No. 3886, formerly KU 320472), adult female, collected on 26 April 2009 (14:00 h) in Sitio Dangay, Barangay Vigo, Municipality of Lubang, Occidental Mindoro Province, Lubang Island, Philippines (13.79995° N, 120.163930° E; WGS 84; 45 m elev. elevation), by J. Fernandez and CDS.

Paratypes (Paratopotypes). Four paratopotypes were also collected in Sitio Dangay, Barangay Vigo, Municipality of Lubang, Occidental Mindoro Province, Lubang Island, Philippines (13.79995° N, 120.163930° E; WGS 84; 45 m elev.), by J. Fernandez and CDS. One adult male (KU 320470) was collected on 24 April 2009 at 14:00 h, two adult females (KU 320471, 320473) were collected on 26 April 2009 at 14:00 h, and one juvenile (KU 320474) was collected on 29 April 2009 at 14:00 h.

Paratypes. One adult male (KU 307755) was collected on 8 December 2005 in Barangay Vigo, Municipality of Lubang, Occidental Mindoro Province, Lubang Island, Philippines (13.826552° N, 120.120514° E; WGS 84; 27 m elev.), by RMB, CDS, and CWL.

Diagnosis. Following recent taxonomic revisions of Brachymeles (Siler et al. 2011; Davis et al. 2014) the new species is assigned to the B. bonitae Complex based on the following suite of morphological characters: (1) limbs present, (2) non-pentadactyl, (3) fore-limbs with 0–3 fingers, (4) hind limbs with 0–2 toes, (5) paravertebral scale rows ≥ 91, (6) presacral vertebrae 47–53, (7) supraoculars four, (8) enlarged, differentiated nuchals present, (9) longitudinal rows of dark spots around the body absent, and (10) auricular opening absent.

Brachymeles ligtas sp. nov. can be distinguished from congeners by the following combination of characters: (1) body size small (SVL 60.7–79.6 mm), (2) fore-limbs bidactyl, (3) hind limbs digitless, (4) limb length short, (5) supralabials six, (6) infralabials six, (7) supraciliaries five, (8) supraoculars four, (9) midbody scale rows 22, (10) axilla–groin scale rows 74–76, (11) paravertebral scale rows 91–93, (12) prefrontal contact absent, (13) frontoparietal contact present, (14) enlarged chin shields in three pairs, (15) nuchals enlarged, (16) auricular opening absent, (17) presacral vertebrae 50, and (18) uniform body color ( Tables 1 , 2 ).

Comparisons. Brachymeles ligtas sp. nov. can be distinguished from other species in the B. bonitae Complex ( B. bonitae , B. isangdaliri , B. mapalanggaon , B. tridactylus ), by the number of presacral vertebrae (50 versus 53 [ B. bonitae ], 51 [ B. mapalanggaon ], 47 [ B. isangdaliri , B. tridactylus ]), and by having bidactyl fore-limbs and digitless hind limbs (versus bidactyl fore-limbs and unidactyl hind limbs [ B. bonitae ], digitless [ B. bonitae , B. mapalanggaon ], unidactyl [ B. isangdaliri ], or tridactyl [ B. tridactylus ]; Table 2 ); further, from B. bonitae by having a greater number of infralabials (6 versus 5) and absence (versus presence) of a fused mental and first chin shield; from B. isangdaliri by having fewer supraciliaries (5 versus 6) and the presence (versus absence) of a third chin shield pair; from B. mapalanggaon by having a longer fore-limb length (1.2–1.4 mm versus 0.8–1.0) and a longer hind limb length (1.6–2.0 mm versus 1.2–1.6); from B. tridactylus by having a shorter fore-limb length (1.2–1.4 mm versus 1.5–2.5); from B. isangdaliri and B. tridactylus by having a greater number of presacral vertebrae (50 versus 47 [ B. isangdaliri , B. tridactylus ]) and a shorter hind limb length (1.6–2.0 mm versus 2.2 [ B. isangdaliri ] or 2.6–3.6 [ B. tridactylus ]); from B. bonitae and B. mapalanggaon by having fewer presacral vertebrae (50 versus 53 [ B. bonitae ] or 51 [ B. mapalanggaon ]), fewer axilla–groin scale rows (74–76 versus 83–90 [ B. bonitae ] or 80–84 [ B. mapalanggaon ]); from B. bonitae , B. isangdaliri , and B. mapalanggaon by having fewer paravertebral scale rows (91–93 versus 103–110 [ B. bonitae ], 97 [ B. isangdaliri ], or 99–102 [ B. mapalanggaon ]); from B. bonitae , B. isangdaliri , and B. tridactylus by the presence of frontoparietals in contact (versus not in contact). Finally, Brachymeles ligtas sp. nov. can be distinguished from all limbless species of Brachymeles by having limbs, and from all pentadactyl species of Brachymeles by having bidactyl fore-limbs and digitless hind limbs.

Description of holotype. Adult female, body small, slender, SVL 79.6 mm; head weakly differentiated from neck ( Fig. 2 , 3 ), nearly as wide as body, HW 5.7% SVL, 96.0% HL; HL 34.2% SnFa; SnFa 17.3% SVL; snout rounded in dorsal and lateral profile, SNL 56.0% HL; ear completely hidden by scales; eyes small, ED 21.3% HL, 50.9% END, pupil subcircular; body slightly depressed, nearly uniform in thickness, MBW 124.7% MBH; scales smooth, glossy, imbricate; longitudinal scale rows at midbody 22; paravertebral scale rows 93; axilla–groin scale rows 76; limbs short, diminutive, bluntly rounded, with digits reduced to two small digit growths on fore-limbs; hind limb digits absent; finger lamellae absent; FLL 2.2% AGD, 1.7% SVL; HLL 3.1% AGD, 2.5% SVL; tail not as wide as body, gradually tapered towards end, TW 88.9% MBW, TL 101.7% SVL.

Rostral projecting onto dorsal snout to level in line with midline of nasal, wider than long, in contact with frontonasal; frontonasal wider than long; nostril ovoid, in anteroventral corner of single trapezoidal nasal, longer axis directed posterodorsally and anteroventrally; supranasals present; postnasals absent; prefrontals moderately separated; frontal roughly diamond-shaped, its anterior margin in moderate contact with frontonasal, in contact with first two anterior supraoculars, 5× wider than anterior supraocular; supraoculars four; frontoparietals moderate, in narrow contact, each contacts supraoculars two and three; interparietal moderate, its length roughly equal to 1.5× midline length of frontoparietal, longer than wide, diamond-shaped, wider anteriorly, pineal eyespot ovoid, visible in center; parietals broader than frontoparietals, in moderate contact behind interparietal; enlarged nuchals present; loreals two, anterior loreal longer and slightly higher than posterior loreal; preocular one; presubocular one; supraciliaries five, the anteriormost contacting prefrontal and separating posterior loreal from first supraocular, posteriormost extending to midline of fourth supraocular; subocular scale row complete, in contact with supralabials; lower eyelid with one row of scales; supralabials six, first twice the width of others, third, fourth and fifth subocular; infralabials six ( Fig. 2 ).

Frontoparietal contact Absent Absent Present Point contact or Absent

Absent

1st chin shield pair contact Absent Absent Present or Absent Absent Present or Absent Mental wider than long, in contact with first infralabials; postmental single, enlarged, its width greater than width of mental; followed by three pairs of enlarged chin shields, first and second pairs moderately separated by single medial scale, second pair largest followed by first pair, third pair smallest, separated by four medial scales ( Fig. 2 ). Scales on limbs smaller than body scales.

Variation. All specimens examined in this series match the holotype closely except one individual (KU 307755) that has the first chin shield pair in contact.

Coloration of holotype in life. ( Fig. 3 ) The dorsal, and lateral portions of the trunk and tail are solid pink-like Beige (Color 254; Köhler 2012). Just above the orbit, a single splotch of Pratt’s Payne’s Gray (Color 293; Köhler 2012) can be seen on the dorsal and lateral portions of the head, as well as Cinnamon-Drab on the snout (Color 50; Köhler 2012).

Coloration of holotype in preservative. The dorsal, lateral, and ventral portions of the trunk and tail are a solid Prout’s Brown (Color 47; Köhler 2012). Just above the orbit, a single splotch of Fuscous (Color 283; Köhler 2012) can be seen on the dorsal and lateral portions of the head. The ventral portion of the head is the same background color as the trunk (Prout’s Brown; Color 47; Köhler 2012).

Etymology. The specific epithet is derived from the Tagalog (Filipino) term "nakaligtas," meaning "survivor" and " ligtas ," meaning "salvation." We name this species in honor of the people of Lubang Island who endured nearly three decades of violence and guerrilla warfare, from 1945 to 1974, led by the Imperial Japanese Army intelligence officer Hiroo Onoda, and four Japanese soldiers. After being driven into the jungle of Lubang Island by allied forces near the end of World War II, Onoda resisted surrender for 29 years believing the war was not yet over. Onoda would finally surrender in 1974, allowing the communities of Lubang to move on from the hardships faced during this time period, including the loss of over 30 lives and injuries to dozens more. Suggested common name: Lubang Slender Skink.

Distribution. Brachymeles ligtas sp. nov. is currently known only from Lubang Island ( Fig. 1 ) and we expect it is found on several smaller nearby landmasses.

Natural history. Brachymeles ligtas sp. nov. likely once occurred in low- to mid-elevation primary forest habitats. As most primary forest on Lubang Island has been destroyed, the recent observations of this species have occurred in secondary growth forest habitats. In contrast to the other members of the B. bonitae Complex, this species appears to be relatively common in secondary growth forest fragments on the island. To date, no other congeners have been documented on Lubang Island.

We have evaluated this species against the International Union for Conservation of Nature (IUCN) criteria for classification and find that it does not qualify for Critically Endangered, Endangered, Vulnerable, or Near Threatened status. Although B. ligtas sp. nov. is known from a single island only, the species appears relatively common in secondary growth forest on Lubang, and until additional data are presented to support otherwise, we classify this species as Least Concern (LC; IUCN 2015).

Figures

FIGURE 1. Map of the Philippine islands, with island labels provided for islands with representative samples used for this study. S = Sibuyan Island; T = Tablas Island.

FIGURE 2. Illustration of head scale patterns of the holotype of Brachymeles ligtas sp. nov. (PNM 9818) in dorsal, lateral, and ventral views. Taxonomically diagnostic head scales are labeled as follows: C, chin shield; F, frontal; FN, frontonasal; FP, frontoparietal; IL, infralabial; IP, interparietal; L, loreal; M, mental; N, nasal; Nu, nuchal; P, parietal; PF, prefrontal; PM, postmental; PO, preocular; PSO, presubocular; R, rostral; SC, supraciliary; SL, supralabial; SN, supranasal; and SO, supraocular. Roman numerals indicate scales in the supraocular series, with Arabic numbers indicating scales in the supraciliary series. Illustrations by MLP and CDS.

FIGURE 3. Photograph of holotype in life of Brachymeles ligtas sp. nov. (PNM 9818). Note: Individual is about to shead, resulting in lighter scale coloration. Photograph taken by CDS.

Tables

TABLE 1. Summary of mensural characters among species of the Brachymeles bonitae Complex. Sample size, body length and total length among males and females, and general geographical distribution (PAIC = Pleistocene Aggregate Island Complexes, sensu Brown & Diesmos [2002]) are included for reference (SVL, TotL, FLL, and HLL given as range over mean ± standard deviation; all body proportions given as percentage over mean ± standard deviation).

	bonitae isangdaliri (3 m, 1 f) (1 f)	ligtas sp. nov. (3 m, 2 f)	mapalanggaon (3 m, 6 f)	tridactylus (12 m, 9 f)
Range	Luzon & Polillo Luzon Island islands	Lubang Island	Masbate Island	West Visayan PAIC
SVL (f)	69.4 59.5	60.7–69.2 (65.0 ± 6.0)	61.7–75.8 (67.2 ± 5.4)	59.9–82.3 (71.4 ± 6.9)

TABLE 2. Summary of meristic and qualitative diagnostic characters (present, absent) among species of the Brachymeles bonitae Complex. The pairs of enlarged scales posterior to the postmental scale are abbreviated as chin shield pairs with reference to the 1 st, 2 nd, and 3 rd pairs (when present). In cases of scale count variation within species, numbers of individuals showing specific counts are given in parentheses.

bonitae (3 m, 1 f)	isangdaliri (1 f)	ligtas sp. nov. (3 m, 2 f)	mapalanggaon (3 m, 6 f)	tridactylus (12 m, 9 f)
Number of digits (fingers/toes) 0/0 1 2/1 1	1/1	2/0	0/0	3/3
PSV 53	47	50	51	47