Parvoscincus tikbalangi, Siler, Cameron D., Linkem, Charles W., Cobb, Kerry, Watters, Jessa L., Cummings, Sean T., Diesmos, Arvin C. & Brown, Rafe M., 2014

Siler, Cameron D., Linkem, Charles W., Cobb, Kerry, Watters, Jessa L., Cummings, Sean T., Diesmos, Arvin C. & Brown, Rafe M., 2014, Taxonomic revision of the semi-aquatic skink Parvoscincus leucospilos (Reptilia: Squamata: Scincidae), with description of three new species, Zootaxa 3847 (3), pp. 388-412 : 404-406

Parvoscincus tikbalangi sp. nov.

( Figs. 3–5 )

Parvoscincus leucospilos: Linkem, Diesmos, Brown, 2011 (part); Linkem & Brown, 2013 (part); Brown et al. 2013b.

Holotype. PNM 9795 (ACD Field No. 1989, formerly KU 327785), adult male, collected on 15 February 2005, in Sitio Apaya, Barangay Dibuluan, Municipality of San Mariano, Isabela Province, Luzon Island, Philippines (N: 17.029°; E: 122.1928°; WGS-84; 600 m in elevation), by ACD.

Paratypes. KU 320522, 327786 collected on 5 February 2005 in Sitio Apaya, Barangay Dibuluan, Municipality of San Mariano, Isabela Province (same coordinates), by ACD. KU 327787–96 collected on 24–26 April 2005 in Barangay Del Pilar, Municipality of San Mariano, Isabela Province (N: 122.104°, E: 16.8592°), by ACD.

Diagnosis. Parvoscincus tikbalangi can be distinguished from congeners by the following combination of characters: (1) body size medium (SVL 41.5–54.7 mm); (2) Toe-IV lamellae 14–16; (3) supralabials seven; (4) infralabials seven; (5) midbody scale rows 28–32; (6) paravertebral scale rows 58–63; (7) prefrontals separated from first supraocular; (8) frontoparietals fused; (9) head pigmentation moderately mottled; (10) upper arm pigmentation present, patchy; (11) subcaudal pigmentation absent; (12) dorsal white spots faint; (13) dorsal white bands 9–12; (14) lateral body coloration present, tan; (15) tail dorsolaterally compressed; and (16) semi-aquatic (Tables 2, 3).

Comparisons. Characters distinguishing Parvoscincus tikbalangi from all species of Parvoscincus are summarized in Tables 2 and 3. Parvoscincus tikbalangi most closely resembles P. duwendorum , P. leucospilos , and P. manananggalae , but differs from P. duwendorum by having seven infralabials (vs. eight); from P. duwendorum and P. manananggalae by having Toe-IV lamellae 13–16 (vs. 12 [ P. duwendorum ], 17 [ P. manananggalae ]); from P. duwendorum by having a greater number of midbody scale rows (28–32 vs. 26) and fewer dorsal white bands (9–12 vs. 15); from P. leucospilos and P. manananggalae by having a tendency towards fewer midbody scale rows (28–32 vs. 30–34 [ P. leucospilos ], 32–33 [ P. manananggalae ]), fewer paravertebral scale rows (58–63 vs. 61–67 [ P. leucospilos ], 61–69 [ P. manananggalae ]), faint dorsal white spots (vs. large and well-defined), and by the presence of tan lateral coloration (vs. presence and bright reddish-orange [ P. leucospilos ], absence [ P. manananggalae ]); from P. leucospilos by having seven supralabials (vs. six or seven), moderate head pigmentation mottling (vs. heavy), the presence (vs. absence) of dark pigmentation on the upper arm surface; and from P. manananggalae by the absence (vs. presence) of dark subcaudal pigmentation.

Description of holotype. Details of the head scalation are shown in Figure 4 . An adult male Parvoscincus , SVL 53.5 mm, with clawed, pentadactyl limbs. Head distinct from neck, characterized by enlarged jaw adductor musculature in temporal region. Snout rounded in dorsal aspect, rounded in lateral aspect; rostral wide forming a nearly straight margin with nasals and frontonasal; frontonasal wider than long, in contact with nasals, rostral, anterior loreal, and prefrontal scales; prefrontals in broad medial contact, in contact with anterior and posterior loreals, frontal, frontonasal, and first supraciliary, separated from first supraocular; frontal greatly longer than wide, in contact with two supraoculars on right, two on left, and first supraciliary, rounded anteriorly, rounded posteriorly; four enlarged supraoculars, first largest; single, large frontoparietal, in contact with supraoculars II–IV; interparietal arrowhead-shaped; parietals in narrow medial contact, in narrow contact with fourth supraocular, in moderate contact with postsupraocular, and secondary temporal; primary temporals two, ventral largest, overlapping dorsal; secondary temporals two, large, dorsal largest, ventral overlapping dorsal; tertiary temporals two, dorsal largest, ventral overlapping dorsal; auricular opening large.

Nasal pierced in center by large naris, surrounded anteriorly by rostral, dorsally by frontonasal, posteriorly by anterior loreal, and ventrally by first and second supralabial; anterior loreal one, narrow, posterior loreal roughly equal in size; preoculars two; supralabials seven, fifth subocular; lower eyelid scaly and semi-transparent, nonscaled “window” absent; ear large, moderately sunk.

Infralabials seven, decreasing in size posteriorly in series; mental small, forming straight suture with single, large postmental and first infralabials; enlarged chin shields in three pairs; gular scales slightly smaller than ventrals.

Body elongate, cylindrical, slender, with 30 equal sized midbody scales, limbs overlapping when adpressed; paravertebral scales 62, imbricate, smooth, without striations, keels or pits. Tail elongate, dorsolaterally compressed, longer than body (TL [85.0] / SVL [53.5] 1.59); subcaudal scales equal to lateral scales for basal half of tail, enlarged for distal half of original tail. Precloacal region with series of enlarged scales between pelvic region and cloaca, more elongate than ventral scales; medial precloacal scales larger; hemipenes everted.

Forelimbs smaller than hind limbs, pentadactyl; forelimb scales slightly smaller in size than body scales, imbricate and smooth, reducing slightly in size distally; lamellae becoming slightly keeled distally on each digit; relative digit length I <V <II <III = IV; palmar scales irregular, raised, formal ventral protrusions from palmar surface. Hind limbs small, pentadactyl; hind limb scales equal in size and shape to body scales; dorsal scales on digits multiple. Lamellae keeled proximally and distally, flat for a few scales in between on Toe-IV; Toe-IV lamellae 16; relative digit length I <II <V <III <IV; plantar scales irregular, slightly raised.

Coloration of holotype in preservative. The background dorsal coloration is dark brown, with a mottled pattern of many different shades of brown. Two faint light brown stripes run longitudinally along the length of the body, with faint light brown spots distributed between. Rows of cream spots are distributed on the dorsolateral surface of the body. The posterior half of the tail is solid medium brown in coloration. The lateral surfaces of the body are heavily mottled dark brown and cream, with small cream spots distributed throughout. The limbs are heavily mottled dark brown and cream, with the exception of a large cream spot on the upper forelimbs, proximate to the body insertion. The ventral surface of the limbs is solid cream in color, with the exception of very faint light brown mottling present on the hands and feet. The ventral portion of the body is solid cream in color to the tip of the tail, which has a medium brown mottled pattern. The dorsal surface of the head is mottled light and medium brown. This mottled color pattern is slightly darker between the eyes. The lateral surface of the head has a slightly lighter brown mottled color pattern. There is a row of six distinct cream spots on the supralabials, which are paired with another six cream spots on the infralabials.

Coloration of holotype in life (Differences from preserved specimens; Fig. 5 ). The cream mottled color pattern and indistinct cream spots present on the lateral surface of the head transition into pale bluish-gray mottled coloration. The lateroventral surfaces of the axilla–groin region of the body and the tail are colored pale orangecream. Within the axilla–groin region and again on the tail, the coloration transitions from more orange in coloration anteriorly to more cream posteriorly. The surface around the upper forelimbs, proximate to the body, is colored light orange-cream.

Measurements and scale counts of holotype in mm. SVL 53.5; AGD 26.7; TotL 138.5; TL 85.0; HL 12.2; HW 7.2; SnFa 18.2; ED 3.1; SNL 3.8; IND 1.8; FLL 5.0; HLL 6.4; MBSR 30; PVSR 62; ToeIVlam 16; SL 7; IFL 7; SO 4.

Variation. We observed the following variation in the degree of contact between head scales: prefrontals in medial contact (KU 320522, 327785–93, 327795, 327796) or separated (KU 327794). Scale pigmentation was observed to vary among the examined series: dark cloacal scale pigmentation was present (KU 320522, 327785, 327791) or absent (KU 327786–90, 327792–96).

Distribution, ecology and natural history. Parvoscincus tikbalangi is known only from northeastern Luzon Island in the Isabela Province ( Fig. 1 ). Samples were found in the Barangays Del Pilar and Dibuluan in the Municipality of San Mariano, in the Sierra Madre Mountain range. This semi-aquatic species of forest skink occurs in primary- and secondary-growth forests, in riparian microhabitats.

At this time we are unable to appropriately evaluate this species against the IUCN criteria for classification due to the lack of available information about its distribution and natural history. We therefore classify this species Data Deficient DD (IUCN, 2010) pending future studies on this unique semi-aquatic forest skink.

Etymology. The specific epithet is a patronym derivation of the name “Tikbalang,” a mythological part man, part horse mountain forest creature from Filipino folklore. Tikbalang is said to jump down from trees to dispatch its unsuspecting victims by decapitation. Suggested common name: Sierra Madres Aquatic Skink.

Figures

FIGURE 1. Map of the Luzon Island, Philippines, showing the collection localities for the new species and P. leucospilos.

FIGURE 3. Dorsal views of representative specimen heads and flanks, exhibiting pigmentation pattern variation among species.

FIGURE 4. Photographs of heads from dorsal and lateral perspectives to show pigmentation and scale pattern variation among species. With the exception of P. leucospilos (KU 313870), all photographs are of the holotypes of the new species.

FIGURE 5. Photographs in life of (A) P. leucospilos (Mt. Banahao; TNHC 62683); (B) P. leucospilos (Angat Watershed; KU 329388); (C) P. manananggalae sp. nov. (PNM 9794); and (D) P. tikbalangi sp. nov. (Holotype; PNM 9795).