Dark-headed Sabah Groundsnake

description

Description of the holotype (FMNH 251054) — metrics (in mm) and pholidosis. An adult female; length 1071 SVL + 188 TL = 1259 TTL, TL 21 % of TTL; head broad, distinct from body; snout rounded in dorsal view, angled in lateral view, mouth subterminal. Rostral character state gull wing + (Fig. 4 A, B). Internasals shorter than wide, with SSR = 0.25. Prefrontal width 2 / 3 of prefrontal length, prefrontal area about three times the area of the internasals; HSR = 0.31. Frontal pentagonal with well-formed corners and a slightly concave anterior suture; AE lies at the same level as the anterior edge of the frontal; FPR = 0.81 (Fig. 4 A); PF 8> 5> 9 = 4> 3> 2 = 1, SL 2 is rectangular whereas SL 1 is triangular (Fig. 4 B, B’). Eye length two-thirds of eye-naris distance; pupil oval; internarial distance 60 % of interorbital distance. Ten infralabials; IL 1 – 5 contacting anterior genials, with two-thirds of the medial border of IL 5 in contact with the anterior genial; three gulars separating the posterior genial from the anterior-most gastrostege; length of mental groove one-third of ventral head length (VHR = 0.38; Fig. 4 C’). Dorsals in 17 - 17 - 15 rows, 214 ventrals, cloacal plate e

Carefully examining Bornean Stegonotus (Serpentes, Colubridae): the montane groundsnake population in Sabah is a new and distinct species

diagnosis

Diagnosis. Stegonotus caligocephalus is a medium-sized (maximum SVL = 1071 mm) snake with a relatively short tail (SCR ♀ = 0.21), the shortest in the genus Stegonotus. It can be distinguished from all other known Stegonotus species by the following combination of characters: (1) rostral extending onto the dorsal part of the head intruding into the internasal area but not reaching the level of the nasals (character state: gull wing +; Fig. 4 A, A’); (2) area of prefrontals three times that of the internasals, internasal suture one-fourth to one-third the length of the prefrontal suture (SSR 0.25 – 0.33, mean = 0.28); (3) frontal clearly pentagonal with well-formed corners and a slightly concave anterior suture; (4) AE lies at the same level as the anterior end of the frontal; (5) length of frontal three-fourths that of the parietal suture (FPR = 0.75); (6) PfS one-fourth to one-third the length of external head-scale length (HSR = 0.25 – 0.31). (7) PF <± 90 ° (102 °); (8) AP <= 122 °, with its lateral ray directed posterolaterally (Fig. 4 A, A’); (9) two temporal scales touching the parietals; (10) three neck scales contacting parietals; (11) loreal as long as wide to one-third long

Carefully examining Bornean Stegonotus (Serpentes, Colubridae): the montane groundsnake population in Sabah is a new and distinct species

etymology

Etymology. The species name caligocephalus is a compound word derived from the Latin caligo, with meanings including dark (ness), out of sight, fog, and the Greek kephalos (κεϕαλοζ) meaning head. We deliberately select a mixed-language name given that this name is designed to have mixed morphological and metaphorical meanings. The species name first of all references the darker head color in this species. Secondly, the dark, looming shape of Mount Kinabalu, Southeast Asia’s tallest mountain and the montane home of S. caligocephalus, is a dramatic, head-like massif, and we wish to remind people that mountain regions are wonderful places to explore and preserve nature.

Carefully examining Bornean Stegonotus (Serpentes, Colubridae): the montane groundsnake population in Sabah is a new and distinct species

materials_examined

Holotype. FMNH 251054 (field number RFI 49331), an adult female from near the Gunung Emas [Gunung Alab] Telekom tower, Crocker Range National Park, Tambunan District, Sabah State, Malaysia, ca. 5.83 ° N, 116.34 ° E (Fig. 1), elevation ca. 1950 m, collected on 19 January 1993 by the American herpetologist Robert F. Inger (1920 – 2019), Curator of Amphibians and Reptiles at the Field Museum, Chicago, Illinois, USA, from 1954 – 1994 (Matsui 2019). Paratype. USNM 130244, an adult female, from “ Bundu Tuhan, Mount Kina Balu, Ranau District, Sabah ” [Malaysia], ca. 6.05 ° N, 116.53 ° E, elevation 1370 m, collected on 1 August 1951 by the American mammalogist David H. Johnson (1912 – 1996), Curator of Mammals at the National Museum of Natural History, Smithsonian Institution, Washington, D. C., USA, from 1941 – 1965 (Perry 2007). Referred specimen. ZMB 47866, a juvenile female from “ Mt. Kinabalu ” (no further locality data), elevation 1500 m, collected on 13 December 1988. Whereas the information in the collection’s ledger indicates that the specimen was collected by the German-South African herpetologist Thomas Ulber, this appears to be an error in both date and time. Ulber (in litt.) v

Carefully examining Bornean Stegonotus (Serpentes, Colubridae): the montane groundsnake population in Sabah is a new and distinct species