Lycodon sidiki Wostl, Hamidy, Kurniawan & Smith, 2017

Nguyen, Tan Van, David, Patrick & Vogel, Gernot, 2024, Expanded description & range extension of Lycodon sidiki Wostl, Hamidy, Kurniawan & Smith, 2017 (Squamata: Colubridae), Zootaxa 5492 (4), pp. 563-581 : 565-575

Redescription of Lycodon sidiki Wostl, Hamidy, Kurniawan & Smith, 2017

( Figures 1–2 , 3A–G , 4A ; Tables 1–2 )

Holotype: MZB.Ophi.598, adult male. Type locality: Between Takengon and Isaq, Aceh Province, Sumatra, Indonesia (04.50611°N, 96.86061°E; altitude 1,614 m asl).

Additional specimens examined (n=8), all from West Sumatra Province, Indonesia: NHMW 23146 :1 (adult female) and NHMW 23146 :2 (subadult female) from Padang , collected by F. Schild in 1900 ; NHMW 23146 : 7 (adult males) , NHMW 23146 : 4 (subadult male) , NHMW 23146 : 5 & 6 (two adult females) , NHMW 23146 : 8 (subadult female), from Padang , collected by F. Schild in 1899 ; NHMW 23149 :1 (one adult male) no specific location, donated by Steindachner in 1900 .

Revised diagnosis. Medium-sized species, maximum total length 830 mm; loreal present (sometimes fused with the prefrontal), usually in contact with eye; dorsal scale rows 17–17–15; 5–7 upper dorsal scale rows feebly keeled at midbody; 195–212 ventrals; 77–91 subcaudals, paired; cloacal plate undivided; 8 supralabials with 3 rd –5 th SL touching the eye; 1 preocular (rarely fused with prefrontal), 2 postoculars; temporals 2+2; dorsal crossbands narrow, cream colored, 25–33 crossbands on dorsum, 10–16 crossbands on tail; venter with discreet bands throughout (based on Wostl et al. 2017 and this study).

Expanded description of the species, including all known specimens (n=9):

Morphology. Body elongate, somewhat laterally compressed; longest known specimen 830 mm long (SVL 650 mm, TaL 180 mm, male; NHMW 23149 :1); longest known female 718 mm long (SVL 555 mm, TaL 163 mm; NHMW 23146 :1)]; tail comparatively long, thin and tapering (Ratio TaL/TL 0.213 –0.239 in males (n=3) and 0.193 –0.227 in females (n=5)). Head subrectangular, elongate, flattened, well-distinct from the neck; snout elongate, strongly flattened, oblique in profile, projecting over the lower jaw; nostril oval, large; eye moderate in size, pupil vertically elliptic.

Body scalation. DSR 17–17–15, the 5–7 upper rows feebly keeled; VEN 195–210 in males (n=4), 207–212 in females (n=5); SC 80–91 in males (n=4), 77–84 in females (n=5); paired; single cloacal plate.

Head scalation. Rostral triangular, hardly visible from above; nasal vertically divided by a furrow below and above the nostril; two small internasals, widely in contact with each other behind the rostral and with prefrontals; two large prefrontals, longer and wider than internasals; rather small, more or less triangular frontal; 2 large parietals, each bordered by three large scales, i.e., 2 upper temporals and one larger paraparietal posteriorly; 1/1 supraocular; 1/1 preocular, above posterior part of loreal; 2/2 subequal postoculars; 1/1 loreal (6/ 9 specimens), sometime fused with prefrontal (3/ 9 specimens), rather elongate and narrow, entering orbit, in contact with SL 2 and 3, preocular, prefrontal and posterior part of nasal; 8/8 SL in all known specimens, SL 1–2 in contact with nasal, SL 3–5 entering orbit, 6 th SL largest; 2+2 (8/ 9 specimens) or rarely 2+3 (1/ 9 specimens) temporals, lower anterior temporal slightly broader than upper; 9 (5/ 9 specimens), less frequently 8 (2/ 9 specimens) or 10 (2/ 9 specimens) infralabials, IL 1–5 in contact with first pair of chin shields anterior and posterior chin shields about same length on right side, on left side anterior larger than posterior, anterior pair wider.

Coloration in preservative (see Figs. 1 , 2 , 3A–G ): Body and tail dark brown, with 25–33 cream crossbands on the body and 10–14 crossbands on tail, anteriorly wider, becoming narrow posteriorly; crossbands about 1 dorsal scale broad middorsally, widening ventrolaterally to about the length of 2–2.5 dorsals. Head uniformly blackishbrown; no collar. Venter dark with clear, rather irregular, cream bands, 6–10 ventrals broad, with 3–5 ventrals between each band.

Comparisons. Lycodon sidiki is morphologically and phylogenetically placed within the Lycodon fasciatus group (eg. Wostl et al. 2017; Wang et al. 2021; Janssen et al 2019; Shu et al. 2024; Nguyen et al. in review; this study) and is overall most similar to other species from the Lycodon fasciatus group, of which we gave the list of included species above. Therefore, the comparisons with these 14 species appear to be the most pertinent. The main diagnostic characters separating Lycodon sidiki from these 14 species are summarized in Table 2 and Figs. 4–5.

L. sidiki is distinguished from L. butleri by having: lower number of VEN in both sexes (195–210 [avg. 204.3] in males, 207–212 [avg. 209.8] in females vs. 216–227 [avg. 223.0] in males, 221–228 [avg. 224.5] in females); lower number of SC in females (77–84 [avg. 81.3] vs. 88–92 [avg. 90.5]; lower number of crossbands on the tail in females (10–14 [avg. 11.2] vs. 15–23 [avg. 18.9].

L. sidiki is distinguished from L. davidi by having: lower number of VEN in males (195–210 [avg. 204.3] vs. 224); lower number of SC in males (80–91 [avg. 84.8] vs. 99); lower number of bands on body in males (25–32 [avg. 28.3] vs. 84); lower number of crossbands on tail in males (13–16 [avg. 14.5] vs. 38); loreal in contact with eye (vs. not in contact); bands on venter present (vs. absent).

L. sidiki is distinguished from L. cavernicolus by having: larger size in males (max SVL 650 mm vs. 406 mm); lower number of VEN in both sexes (195–210 [avg. 204.3] in males, 207–212 [avg. 209.8] in females vs. 245 in male, 232 in female); lower number of SC in both sexes (80–91 [avg. 84.8] in males, 77–84 [avg. 81.3] in females vs. 113 in male, 92 in female); lower number of crossbands on body in both sexes (25–32 [avg. 28.3] in males, 25–33 in females vs. 45 in male, 36 in female); lower number of crossbands on tail in both sexes (13–16 [avg. 14.5] in males, 10–14 [avg. 11.2] in females vs. 41 in male, 29 in female).

L. sidiki is distinguished from the morphologically similar L. fasciatus by having: slightly smaller size in both sexes (max SVL 650 mm in males, 555 mm in females vs. 706 mm in males, 604 mm in females); slightly higher ratio TaL/TL in males (0.21–0.24 [avg. 0.23] vs. 0.20–0.22 [avg. 0.21]); colour of crossbands (whitish or cream vs. brown or grayish-brown). In L. sidiki there is a tendency to a fusion of the loreal with the prefrontal (3/ 9 specimens on both sides), a character which was not observed in the 44 specimens of L. fasciatus that were examined (see Appendix I). Furthermore, L. sidiki is widely separated from L. fasciatus on a geographical basis, as the latter species inhabits China, Myanmar, India, Bhutan, Thailand, Northern Laos, and Northwest Vietnam. Moreover, L. butleri and L. cavernicolus separate the ranges of both species.

L. sidiki is distinguished from L. gammiei by having: smaller size in females (max SVL 555 mm vs. 1,110 mm); lower number of SC in both sexes (80–91 [avg. 84.8] in males, 77–84 [avg. 81.3] in females vs. 101–110 [avg. 105.5] in males, 101–112 [avg. 107.0] in females); lower number of crossbands on the body in both sexes (25–32 [avg. 28.3] in males, 25–33 [avg. 27.4] in females vs. 42–57 [avg. 49.5] in males, 43–58 [avg. 49.5] in females); loreal in contact with eye (vs. not in contact); colour of crossbands (whitish or cream vs. yellow).

L. sidiki is distinguished from L. gongshan by having: smaller size in both sexes (max SVL 650 mm in males, 555 mm in females vs. 740 mm in males, 798 mm in females); lower number of SC in females (77–84 [avg. 81.3] vs. 92–94 [avg. 93.0]); lower number of crossbands on the body in females (25–33 [avg. 27.4] vs. 32–36 [avg. 34.3]).

L. sidiki is distinguished from L. liuchengchaoi by having: smaller size in females (max SVL 555 mm vs. 670 mm); lower number of SC in males (80–91 [avg. 84.8] vs. 68–81 [72.7]); lower number of crossbands on the body in males [25–32 [avg. 28.3] vs. 40–45 [avg. 43.3]); colour of crossbands (whitish or cream vs. yellow).

L. sidiki is distinguished from L. multifasciatus by having: larger size in males (max SVL 650 mm vs. 490 mm); lower number of VEN in both sexes (195–210 [avg. 204.3] in males, 207–212 [avg. 209.8] in females vs. 237 in males, 227–232 [avg. 229.8] in females]; lower number of SC in both sexes (80–91 [avg. 84.8] in males, 77–84 [avg. 81.3] in females vs. 117 in males, 106–108 [avg. 107.0] in females); lower number of crossbands on body in both sexes (25–32 [avg. 28.3] in males, 25–33 in females vs. 72 in male, 51–60 [avg. 56.8] in females); lower number of crossbands on tail in both sexes (13–16 [avg. 14.5] in males, 10–14 [avg. 11.2] in females vs. 35 in male, 25–32 [avg. 28.7] in females); loreal in contact with eye (vs. not in contact); ventral pattern (banded vs. uniform).

L. sidiki is distinguished from L. multizonatus by having: larger size in males (max SVL 650 mm vs. 505 mm); higher ratio TaL/TL in males (0.21–0.24 [avg. 0.23] vs. 0.16–0.18 [avg. 0.17]); higher number of SC in males (80–91 [avg. 84.8] vs. 56–75 [avg. 65.5]); lower number of crossbands on the body in males (25–32 [avg. 28.3] vs. 55–62 [57.8]); temporals 2+2 (vs. 2+3); cloacal plate (undivided vs. divided); ventral pattern (banded vs. uniform); colour of crossbands (whitish or cream vs. pink).

L. sidiki is distinguished from L. obvelatus by having: larger size in males (max SVL 650 mm vs. 447 mm); higher ratio TaL/TL in males (0.21–0.24 [avg. 0.23] vs. 0.19]); higher number of SC in males (80–91 [avg. 84.8] vs. 76]; dorsal scales keeled vs. smooth; ventral pattern (banded vs. uniform); colour of body crossbands (whitish or cream vs. salmon).

L. sidiki is distinguished from L. pictus by having: larger size in males (max SVL 650 mm vs. 500 mm); lower number of VEN in males (195–210 [avg. 204.3] vs. 209–215 [avg. 212.0]); lower number of SC in females (77–84 [avg. 81.3] vs. 85–91 [avg. 89.0]); dorsal scales keeled (vs. smooth); ventral pattern (banded vs. uniform).

L. sidiki is distinguished from L. ruhstrati abditus by having: smaller size in both sexes (max SVL 650 mm in males, 555 mm in females vs. 761 mm in males, 762 mm in females); lower number of VEN in both sexes (195–210 [avg. 204.3] in males, 207–212 [avg. 209.8] in females vs. 206–224 [avg. 217.2] in males, 220–229 [avg. 224.2] in females); lower number of SC in both sexes (80–91 [avg. 84.8] in males, 77–84 [avg. 81.3] in females vs. 85–102 [avg. 93.9] in males, 82–106 [avg. 97.1] in females); lower number of crossbands on body in males (25–32 [avg. 28.3] vs. 31–46 [avg. 36.9]); loreal in contact with eye (vs. not in contact).

L. sidiki is distinguished from L. ruhstrati ruhstrati by having: smaller size in both sexes (max SVL 650 mm in males, 555 mm in females vs. 810 mm in males, 672 mm in females); lower number of VEN in both sexes (195–210 [avg. 204.3] in males, 207–212 [avg. 209.8] in females vs. 211–228 [avg. 217.7] in males, 216–228 [avg. 220.4] in females); lower number of SC in both sexes (80–91 [avg. 84.8] in males, 77–84 [avg. 81.3] in females vs. 105–114 [avg. 107.4] in males, 97–108 [avg. 103.0] in females); lower number of crossbands on body in both sexes (25–32 [avg. 28.3] in males, 25–33 [avg. 27.4] in females vs. 37–46 [avg. 41.6] in males, 33–40 [avg. 36.4] in females]; lower number of crossbands on tail in both sexes (13–16 [avg. 14.5] in males, 10–14 [avg. 11.2] in females vs. 16–25 [avg. 21.3] in males; 14–22 [avg. 18.5] in females); loreal in contact with eye (vs. not in contact).

L. sidiki is distinguished from L. serratus by having: larger size in males (max SVL 650 mm vs. 480 mm); lower number of crossbands on body in males (25–32 [avg. 28.3] vs. 66]); lower number of crossbands on tail in males (13–16 [avg. 14.5] vs. 26); dorsal scales keeled (vs. smooth); ventral pattern (banded vs. uniform); colour of crossbands (whitish or cream vs. tawny olive).

L. sidiki is distinguished from L. synaptor by having: slightly larger size in males (max SVL 650 mm vs. 550 mm); slightly higher ratio TaL/TL in females (0.19–0.23 [avg. 0.21] vs. 0.18–0.21 [avg. 0.19]); higher number of VEN in both sexes (195–210 [avg. 204.3] in males, 207–212 [avg. 209.8] in females vs. 186–199 [avg. 191.8] in males, 190–203 [avg. 194.9] in females); slightly higher number of SC in females (77–84 [avg. 81.3] vs. 67–77 [avg. 70.9]).

Distribution ( Fig. 6 ). Lycodon sidiki was previously known only from Aceh Province, Sumatra, Indonesia ( Wostl et al. 2017). We here add a second locality from Padang, West Sumatra Province. The new location in Padang is ca. 710 airline kilometers southeast of the type locality. It also represents the southernmost locality of the Lycodon fasciatus species group. Given its geographic proximity, it likely occurs in several forests of Sumatra; in particular, records in the highlands of the provinces of North Sumatra, Riau, and Jambi are anticipated.

Figures

FIGURE 1. Lycodon sidiki in preservative, specimen NHMW 23149:1 (male) in West Sumatra, Indonesia—(A) General dorsal view; (B) General ventral view; (C) Lateral view of the head, right side; (D) Lateral view of the head, left side; (E) Dorsal view of the head; (F) Ventral view of the head. Photos by G. Vogel.

FIGURE 2. Lycodon sidiki in preservative, from Sumatra, Indonesia—(A) NHMW 23146:1 (adult female); (B) NHMW 23146:2 (subadult female); (C): NHMW 23146:4 (adult male); (D) NHMW 23146:5 (adult female); (E) NHMW 23146:6 (adult female); (F) NHMW 23146:7 (adult male). Photos by G. Vogel.

FIGURE 3. Lateral view of the head, right side, of Lycodon sidiki and L. subcinctus from Padang, West Sumatra, Indonesia—L. sidiki: (A) NHMW 23146:1 (adult male); (B) NHMW 23146:2 (subadult female); (C) NHMW 23146:4 (subadult male); (D) NHMW 23146:5 (adult female); (E) NHMW 23146:6 (adult female); (F) NHMW 23146:7 (adult male); (G) NHMW 23146:8 (subadult female).—L. subcinctus: (H) NHMW 23146:9 (subadult female); (I) SMF 22442 (subadult male). Photos by G. Vogel.

FIGURE 4. Photos in life of Lycodon sidiki compared with other species of the L. fasciatus group (Part 1). (A) L. sidiki in Aceh, Sumatra, Indonesia; (B) L. butleri in Fraser’s Hill, Selangor, Malaysia; (C) L. cavernicolus in Gua Wang Burma, Perlis, Malaysia; (D) L. davidi in Vang Vieng, Vientiane, Laos; (E) L. fasciatus in Aizawl, Mizoram, India; (F) L. gammiei in Eaglenest WS, Arunachal Pradesh, India; (G) L. gongshan in Nujiang, Yunnan, China; (H) L. liuchengchaoi in Lishui, Zhejiang, China. Photos by: (A) reproduced from Wostl et al. (2017); (B) R. Grassby-Lewis; (C) M.A. Muin; (D) reproduced from Vogel et al. (2012); (E) P. Shinde; (F) C. Sheth; (G) S.C. Shi; and (H) F. Gao.

FIGURE 6. Map showing distributions of the Lycodon fasciatus group in Malay Peninsula and Sumatra including: L. butleri, L. cavernicolus, and L. sidiki. Notes: numbers indicate the different localities where these species have been recorded (see Appendix II for the details of localities).