Stegonotus caligocephalus KAISER, LAPIN, O’SHEA & KAISER, 2020
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Stegonotus caligocephalus
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| Higher Taxa | Colubridae, Colubrinae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes) |
| Subspecies | |
| Common Names | E: Dark-headed Sabah Groundsnake |
| Synonym | Stegonotus caligocephalus KAISER, LAPIN, O’SHEA & KAISER 2020 |
| Distribution | Malaysia (Borneo: Sabah) Type locality: 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 |
| Reproduction | |
| Types | Holotype. FMNH 251054 (field number RFI 49331), an adult female, 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). Other specimens: ZMB 47866 |
| 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. 4A, 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. 4A, A’); (9) two temporal scales touching the parietals; (10) three neck scales contacting parietals; (11) loreal as long as wide to one-third longer than wide (LSR = 0.6–1.0); (12) two preoculars, upper preocular 25% larger than lower one (Fig. 4B, B’); (13) nine supralabials, two (SL4–5) touching the eye; SL5 larger than SL4 (Figs. 4B, B’); (14) ten infralabials, five (IL1–5) touching the anterior genial (Fig. 4C’); (15) three gulars separating the posterior genials and the anterior-most gastrostege; (16) 17-17-15 dorsals; 211–218 (mean = 214 ± 2.9) ventrals, 56–65 (mean = 61 ± 3.7) paired subcaudals; (17) cloacal plate entire; (18) color in preservative (27 years post-collection): dorsum Tawny Olive (17) with some dark spots on lateral edge of a few rows of dorsal scales, head Grayish Olive (273) with some scattered lighter areas in Olive Gray (265). The supralabials and infralabials are Pale Buff (11) with mottled areas of Drab Gray (256) (Figs. 3A, 4A, B). The venter is Pale Horn Color (11) with dark areas on the anterior edge of the ventral scales and a dark “dot” on the lateral edge (Burnt Sienna, 38); the anterior one-third of the subcaudals are Burnt Sienna (38), creating a dark tail (Fig. 3B in Kaiser et al. 2020). |
| Comment | Similar species. The species could, in principle, be confused with three similarly colored species (Stuebing et al. 2014). Lycodon albofuscus4 has keeled scales, is more slender, and its lowland habitat make it unlikely that this species occurs in sympatry with S. caligocephalus. On Borneo, older individuals of Lycodon subcinctus may have lost the characteristic light bands of younger snakes and may present an overall body coloration similar to S. caligocephalus. As is the case with L. albofuscus, the range of L. subcinctus may not extend into the higher elevations (above 1000 m) where S. caligocephalus is found (Kaiser et al. 2020). |
| 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. 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. |
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