Stegonotus borneensis Inger, 1967 :82

Kaiser, Christine M., Kaiser, Hinrich & O’Shea, Mark, 2018, The taxonomic history of Indo-Papuan groundsnakes, genus Stegonotus Duméril et al., 1854 (Colubridae), with some taxonomic revisions and the designation of a neotype for S. parvus (Meyer, 1874), Zootaxa 4512 (1), pp. 1-73 : 52-54

Stegonotus borneensis Inger, 1967:82

Taxonomic status. Valid.

Synonyms. None.

Original name. Stegonotus borneensis Inger, 1967:82 . The species description was presented in English.

Type specimens. FMNH 164746 (holotype; Table 1) and USNM 130244 (paratype), both adult females ( Fig. 30 ) .

Type localities. The holotype is from “Nanga Tekalit, Kapit District, Third Division, Sarawak ” [ Malaysia] with GPS coordinates given as 1°38’N, 113°35’E [ca. 1.63°N, 113.58°E, elevation ca. 56 m]. The paratype was collected at “Bundu Tuhan, Mount Kina Balu, Ranau District, Sabah ” [ Malaysia], with GPS coordinates given as “ 6°03'N, 116°32'E ” [ca. 6.05°N, 116°53’E] and a listed elevation of 1370 m. The two type localities are separated by a distance of ca. 650 km by air and by an elevation of over 1300 m.

Collection. The holotype was collected on 24 May 1963 by F. Wayne King (born 1936), Curator Emeritus at the Florida Museum of Natural History in Gainesville, Florida, USA. The paratype was collected on 1 August 1951 by David H. Johnson (1912–1996), curator of mammals at the National Museum of Natural History , Smithsonian Institution, Washington, D.C., USA, from 1941–1965 .

Key characteristics of the type specimens. Holotype: 783 (715) mm SVL + 221 19 (221) mm TL = 1004 (936) mm TTL. V ♀ = 194 (193), SC ♀ = 79 (78), SCR ♀ = 0.29 (0.29), D = 21 20 -17-15 (17-17-15), SL E = 4+5 (4+5), SL = 9 (9), IL = 10 (10), IL G = 5 (5) . Paratype: 910 (965) mm SVL + 221 (191) mm TL = 1004 (1156) mm TTL. V ♀ = 218 (218), SC ♀ = 79 (62), SCR ♀ = 0.29 (0.22), D = 21-17-15 (17-17-15), SL E = 4+5 (4+5), SL = 9 (9), IL = 10 (10), IL G = 5 (5).

Key characteristics of the species. We have been able to examine five specimens of S. borneensis . Of these, two (1 ♀, 1 ♂) were collected in lowland localities in Sarawak, whereas the other three (3 ♀♀) were collected at montane elevations (> 800 m) in Sabah. It is of considerable taxonomic interest that the two specimens that were used to define a single species possess quite disparate characteristics. The values of ventral and subcaudal scales (V ♀ = 193, V ♂ = 196 and SC ♀ = 78, SC ♂ = 78 in Sarawak, V ♀ = 211–218 and SC ♀ = 56–65 in Sabah), including the concomitant values of SCR (0.29 for the female and 0.28 for the male in Sarawak, a range of 0.21–0.24 for the females in Sabah) are non-overlapping and quite distinctive, given the distribution and variation of these characters in other species of Stegonotus . Furthermore, in his original description Inger (1967) already presented another feature to distinguish between the Sabah and Sarawak forms. He noted that the vertebral scale row was “enlarged and truncate” in the Sarawak specimen and “less conspicuously enlarged” in the Sabah specimen. We conclude that the evidence shows that the high-elevation form from Sabah should be considered distinct at the species level. Our description of this form will appear in a separate publication (C. Kaiser & H. Kaiser, in press).

The population from Sarawak will retain the name S. borneensis , and based on values of SCR, there does not appear to be any sexual dimorphism in relative body length. Given the limited data from the two available specimens (FMNH 164746, 188500), we expect this species to be characterized by a relatively high ventral count (195 ± 5 in both sexes), medium range subcaudal count (80 ± 5 in both sexes), and SCR in the high 20% range. We expect other features, including the numbers of supralabials (9), infralabials (10), SL E (4+5), and IL G (5) to be constant in the species.

Comments. The skull of the holotype was removed for detailed examination, which can perhaps account for some of the differences between the original and our measurements of SVL. For a better characterization of the species from both Sarawak and Sabah, it is essential that additional material should be collected. Furthermore, it would be interesting to determine whether the species also occurs in the lowland forests of Kalimantan, the Indonesian part of Borneo.

Figures

FIGURE 30. Type specimens of Stegonotus borneensis Inger, 1967. Photos include views of the entire body of the holotype FMNH 164746, an adult female (TTL = 936 mm) in (A) dorsal and (B) ventral views, and of the specimen’s head in (C) dorsal, (D) right lateral, and (E) ventral views. The body of the paratype USNM 130244 is shown in (F) dorsal and (G) ventral views, and the specimen’s head in (H) dorsal, (I) right lateral, and (J) ventral views.