Levitonius mirus, Weinell & Paluh & Siler & Brown, 2020

Weinell, Jeffrey L., Paluh, Daniel J., Siler, Cameron D. & Brown, Rafe M., 2020, A New, Miniaturized Genus and Species of Snake (Cyclocoridae) from the Philippines, Copeia 108 (4), pp. 907-923 : 912-917

Levitonius mirus , new species urn:lsid:zoobank.org:act:27901547-0A54-4733-8F8D-63FEEF810971

Waray Dwarf Burrowing Snake

Figures 1–8 , Tables 1–3

Holotype.— PNM 9872 (formerly KU 337269 ; field tag number RMB 19087 ), adult male ( Figs. 7A , 8 ), Barangay San Rafael , Taft, Eastern Samar Province, Samar Island, Philippines, elevation 187 m above sea level (asl), 11.8298N, 125.2768E, Kerry Cobb and Rafe M. Brown, 1900–2100 hrs, 17 June 2014.

Paratypes.— KU 305488 (field number CDS 1846 ), adult male ( Fig. 7C ), Taft Forest , Barangay San Rafael , Taft, Eastern Samar Province, Samar Island, Philippines, elevation 188 m asl, 11.8328N, 125.2838E, Cameron D. Siler and Charles Linkem, 16 June 2006 ; KU 311281 (field number CDS 3403 ), adult female ( Fig. 7B ), Pilim , Barangay San Vicente , Baybay, Leyte Province, Leyte Island, Philippines, elevation 490 m asl, 10.7418N, 124.8428E, Cameron D. Siler, approximately 1200 hrs, 1 January 2007 .

Diagnosis.— Levitonius mirus can be distinguished from all other SE Asian snake species by having the following combination of characters: small size (largest total length known 172.1 mm); five supralabial scales; 15 longitudinal rows of dorsal scales throughout length of body; subcaudal scales unpaired; pair of internasal scales present; anterior temporal scale present; preocular scale absent; loreal scale present, not in contact with eye; mental scale broadly in contact with anterior chin shields; scales smooth, iridescent; dorsum ground color may be light brown to nearly black; one pale transverse band present on posterior of head, crosses parietals, temporals, and posterior supralabials; pale midventral line present or absent.

Description of holotype.— Adult male; snout–vent length 136 mm; tail length 29 mm; 107 smooth ventral scales; 30 unpaired subcaudal scales; anal scale undivided. Head length 7.3 mm; head width 3.7 mm; head height 2.6 mm. Eye diameter 0.7 mm; pupils subcircular. Supralabials five, third in contact with prefrontal, third and fourth in contact with eye, fourth in contact with postocular, fourth and fifth in contact with primary temporal, fifth in contact with lower secondary temporal. Infralabials six, first pair separated from each other by mental scale, first three contact first chin shield, third and fourth contact second chin shield. Rostral scale slightly taller than wide. Nasal scale divided, surrounds small nostril, in contact with first and second supralabials. Single loreal scale, elongate, not in contact with eye, in contact with nasal, second and third supralabials, prefrontal, and internasal. Preocular and subocular scales absent; one supraocular; one postocular. One large primary temporal; two secondary temporals (one upper, one lower). Dorsal surface of head includes two internasals in contact with each other medially, two prefrontals in contact with each other medially and in contact with eye, two supraoculars separated by frontal scale, and two parietals in contact with each other medially. Mental scale wider than long and wider than rostral. First pair of chin shields in contact with mental scale, each other medially, and twice as long as second pair; second pair of chin shields separated from each other by first genial scale. Five enlarged genial scales anterior to first ventral scale. Ventral scales smooth. Dorsal scales smooth, without apical pits, in 15 parallel (rather than oblique) longitudinal rows throughout length of body; vertebral scales not enlarged compared to other dorsal body scales; posterior vertebrocaudal scales enlarged compared to other dorsocaudal scales; dorsocaudal scale row reduction formula: 10 2 þ 3 ð 2 Þ 9 1þ 2 ð4Þ 1þ 2ð4Þ 7 3 þ 4ð16Þ 3þ 4ð16Þ 5 2 þ 3ð28Þ 2þ 3ð27Þ 3(30).

Skull highly ossified and basicranium is fused ( Fig. 3 ); descending processes of parietal bone short; supratemporal and postorbital bones highly reduced ( Figs. 3 , 4 ); prefrontal bone anteriorly extended around septomaxilla; anterior-lateral edge of parietal bone extends around lateral edge of frontal bone; stapes mostly enclosed by crista circumfenestralis; vertebrae 144 (114 precloacal, 30 caudal; Fig. 5A ). Dentary teeth 27 (left), 26 (right), subequal in size; maxillary teeth 25 (left and right), subequal in size; palatine teeth 16 (left) and 14 (right), subequal in size; pterygoid teeth 29 (left) and 30 (right), subequal in size.

Coloration of the holotype in preservative.— After formalinfixation and preservation in ethanol, ground color of dorsal and lateral surfaces of head, body, and tail fuscous (color 283; Köhler, 2012); each scale mottled with tiny unpigmented patches barely visible without optical magnification. Incomplete pale (unpigmented) transverse bar present on head posterior to eyes, crossing parietals, anterior temporal, and fourth and fifth supralabials ( Fig. 7 ). Anterior-ventral surface of head fuscous with small, irregular shaped unpigmented markings ( Fig. 7 ). Posterior-ventral surface of head with small irregular shaped fuscous markings, otherwise unpigmented ( Fig. 7 ). Ventral body scales medially unpigmented, some fuscous flecks; laterally fuscous ( Fig. 7 ).

Variation.— The paratypes differ from the holotype in the following ways: KU 311281: six medial gular scales between posterior chin shields and first ventral; ventrals 122; subcaudals 17; fifth infralabial contacts third and fourth chin shields (vs. third); dorsocaudal scale row reduction formula: 9 2

2 þ þ 3 3 ð ð 3 3 Þ Þ 7 3 3 þ þ 4 4 ð ð 10 9 Þ Þ 5 1 1 þ þ 2 2 ð ð 16 16 Þ Þ 3(17). Dorsal and lateral surfaces of head, body, and tail raw sienna (color 32; Köhler, 2012; vs. fuscous; Fig. 7B ).

KU 305488: ventrals 124; subcaudals 31; dorsocaudal reduction formula: 13 2 2 þ þ 3 3 ð ð 2 2 Þ Þ 11 2 þ 3 5 ð 4 þ Þ 6;5 ð 4 þ Þ 6 ð 4 Þ 82 þ 3 ð 5 Þ 7 3 3 þ þ 4 4 ð ð 16 17 Þ Þ 5 2 2 þ þ3 3 ð ð 27 27 Þ Þ 3(31). Dorsal and lateral surfaces of head, body, and tail russet ( Köhler, 2012; vs. fuscous; Fig. 7C ); ventral surfaces of head, body, and tail russet (vs. fuscous with unpigmented midventral stripe; Fig. 7C ).

Percent genetic distance (p-distance) is lowest between the holotype and the paratype from Leyte Island ( PNM 9872 vs. KU 311281 : p-distance ¼ 3.95 % at Cyt b and 0 % at CMOS), intermediate in amount between the holotype and Samar Island paratype ( PNM 9872 vs. KU 305488 : p-distance ¼ 14.34 % at Cyt b and 0.18 % CMOS), and highest between the two paratypes ( KU 311281 vs. KU 305488 : p-distance ¼ 16.83 % at Cyt b and 0.19 % at CMOS) .

Comparisons.— This new species is most likely to be confused with juveniles of the genera Cyclocorus , Hologerrhum , Myersophis , and Oxyrhabdium , as well as adults and juveniles of Calamaria and Pseudorabdion . Levitonius mirus can be distinguished from all species of Calamaria , Myersophis , Oxyrhabdium , and Pseudorabdion by having unpaired subcaudals (vs. paired). Additionally, from species of Oxyrhabdium , the new species can be distinguished by its much smaller adult body size, by having a pale transverse bar on the head that is centered over the parietals (vs. on the nuchals or absent), five supralabials (vs. 6–8), 107–124 ventrals (vs..150), and by having 17–31 subcaudals (vs. 33–70); from members of Calamaria and Pseudorabdion by having parietals separated from the supralabials by a large anterior temporal scale (vs. parietals in contact with the supralabials); from all species of Calamaria by having 15 longitudinal rows of dorsal scales (vs. 13); from all species of Cyclocorus and Hologerrhum by its much smaller adult body size, and by having a narrow snout (vs. relatively broad), five supralabials (vs. seven or eight), and by having 15 longitudinal rows of dorsal scales (vs. 17).

Natural history.— The three specimens were all collected between 187–490 m asl. The field notes for the paratype KU 311281 state that it was collected ‘‘in secondary forest in a decaying log.’’ Specimens were all collected by raking fossorial habitats (loose soil beneath rotting logs, woody forest floor debris, leaf litter, etc.). Additionally, the new species’ small size, reduced number of scales on the head, heavily ossified skull, smooth and iridescent scales, small eyes and nostrils, small neural spine of vertebrae, and additional cranial characteristics (see Discussion) all suggest that Levitonius mirus is fossorial ( Gower, 2003; Cundall and Irish, 2008; Yi and Norell, 2015; Palci et al., 2017). In addition to the new species, 33 snake species are known to occur on Leyte or Samar Islands, including seven that are either fossorial or semi-fossorial: Calamaria gervaisii , C. lumbricoidea , Calliophis philippina , Cyclocorus nuchalis taylori , Malayotyphlops ruber , Ramphotyphlops marxi , and Ramphotyphlops olivaceus ( Leviton et al., 2018) . Notably, species of Pseudorabdion have not been recorded from either Leyte or Samar, despite the presence of this genus on nearby islands such as Mindanao ( Leviton et al., 2018), suggesting that L. mirus may replace Pseudorabdion in occupying a portion of the fossorial snake niche in Samar and Leyte. More specimens of L. mirus are needed to understand the ecology, distribution, phenotypic diversity, and genetic diversity of this species.

Distribution.— The new species is currently only known from Samar and Leyte Islands, southeastern Philippines.

Etymology.— The species epithet mirus is a Latin adjective, meaning unexpected finding or surprise—a fitting specific epithet for the miniaturized, phylogenetically unique evolutionary lineage represented by the new genus and species described here. The suggested common name, the Waray Dwarf Burrowing Snake, honors the Waray-waray people of the eastern Visayas, in particular the Samareños who live in vicinity of the type locality, among the forested mountains of Samar Island, and the Leyteños who inhabit the new genus’ only other documented locality in the montane forests of Leyte Island.

Remarks.— Our finding that PNM 9872 from San Rafael, Samar Island is much more closely related to the Leyte Island individual than to the other Samar individual is unexpected ( Fig. 2 ), and suggests that additional species-level diversity may exist within Levitonius on Samar Island. The presence of a pale mid-ventral stripe on both PNM 9872 and KU 311281 (which is absent on KU 205488) is consistent with this multiple-species hypothesis ( Fig. 7 ). However, we conservatively treat the three individuals of Levitonius as a single species until additional specimens and genetic samples can be analyzed.

Figures

FIG. 1. (A) Elevation map of the Philippines, showing location of islands and PAICs mentioned in this article; B.I. ¼ Babuyan Island Group, Sb. ¼ Sibuyan Island, Sq. ¼ Siquijor Island, C.S. ¼ Camiguin Sur, Tb. ¼ Tablas. (B) Samar, Leyte, and nearby islands; red star indicates the type locality of Levitonius mirus, new genus and species; blue circle indicates a second occurrence locality; (C) karst rainforest habitat at the L. mirus, new genus and species, type locality (Barangay San Rafael, Municipality of Taft, Samar Island).

FIG. 2. IQ-TREE phylogeny of Cyclocoridae inferred from Cyt b and CMOS genes; Levitonius mirus, new genus and species, samples highlighted in gray; values at internal nodes indicate ultrafast bootstrap support, and values 95 were considered strong support; branch lengths indicate substitutions/site. See Data Accessibility for tree file.

FIG. 3. Dorsal (left column), lateral (center column), and ventral (right) views of the skulls of representative cylocorine species. White scale bars ¼ 1 mm.

FIG. 4. Comparison of selected cranial bones of cyclocorid species. (A) Skull of Levitonius mirus, new genus and species, showing the position of bones i–iv; from left to right: bones of L. mirus, new genus and species, Myersophis alpestris, Oxyrhabdium leporinum, Hologerrhum philippinum, and Cyclocorus lineatus; i ¼ postorbital bone, ii ¼ supratemporal bone, iii ¼ quadrate bone, and iv ¼ maxilla. White scale bars ¼ 1 mm.

FIG. 5. Comparison of vertebrae of Levitonius mirus, new genus and species, and other cyclocorid species. (A) Whole skeleton (transparent) of L. mirus, new genus and species, showing the position of structures i–iv; (B) from left to right: L. mirus, new genus and species, Myersophis alpestris, Oxyrhabdium leporinum, Hologerrhum philippinum, and Cyclocorus lineatus; (A–B) i ¼ precloacal vertebra at midbody, ii ¼ cloacal vertebra, iii ¼ caudal vertebra midway along tail; (A) iv ¼ hemipenes. White scale bar ¼ 5 mm (A), 1 mm (B).

FIG. 6. Shape and position of the inner ear endocasts within the skulls (transparent) of representative cyclocorid species; asc ¼ anterior semicircular canal; v ¼ vestibule; red ¼ bony labyrinth; blue ¼ stapes; black scale bars ¼ 1 mm.

FIG. 7. Photographs of Levitonius mirus, new genus and species, type specimens (alcohol preserved): holotype PNM 9872 (A), and paratypes KU 311288 (B) and KU 305488 (C). Dorsal view of body (A, top left; B–C, left); ventral view of body (A, bottom left; B–C, center); dorsal view of head (A– C, top right); lateral view of head (A–C, center right); ventral view of head (A–C, bottom right). Thick black scale bars ¼ 10 mm; thin black scale bars ¼ 1 mm.

FIG. 8. Head scalation of Levitonius mirus, new genus and species, holotype (PNM 9872); (A) ventral, (B) lateral, and (C) dorsal views of head. Illustrations by Errol D. Hooper (2019). Black scale bar ¼ 1 mm.