Asthenodipsas borneensis, Quah & Grismer & Lim & Anuar & Chan, 2020

Quah, Evan S. H., Grismer, L. Lee, Lim, Kelvin K. P., Anuar, M. S. Shahrul & Chan, Kin Onn, 2020, A taxonomic revision of Asthenodipsas malaccana Peters, 1864 (Squamata Pareidae) with a description of a new species from Borneo, Zootaxa 4729 (1), pp. 1-24 : 13-17

Asthenodipsas borneensis sp. nov.

urn:lsid:zoobank.org:act:51657C98-84D4-4B74-8AF3-7695E8D72FFB

Bornean Dark-necked Slug Snake

Fig. 2 & 3 .

Asthenodipsas malaccanus (in part): Chan-ard et al. 2015: 159; Charlton 2020: 86–87; Das 2006a: 007, Das 2010: 161 & 344–345, Das 2012 & 2018: 131; Iskandar & Colijn 2001: 111; Marlon 2014: 27–28; Stuebing et al. 2014: 87; Teynié et al. 2010: 39; Wallach et al. 2014: 59. Amblycephalus malaccanus (in part): Boulenger 1892: 507, 1896: 442–443, 1912: 209–210; Flower 1896: 896, 1899: 607 &

694; de Rooij 1917: 267–277; Internatus malaccanus (in part): David & Vogel 1996: 137–138; Malkmus et al. 2002: 343. Pareas malaccanus (in part): De Haas 1950: 529; Haile 1958: 766; Grandison 1972: 92; Marlon 2014: 27–28; Stuebing 1991:

331; Stuebing & Inger 1999: 88; Taylor 1965: 686; Welch 1988: 90. Pareas carinatus: Das 2006b: 45, 2007: 161 .

Holotype. Adult female FMNH 243935 collected by Robert F. Inger and Tan Fu Lian on 25 August 1990 from Mendolong camp watershed, Sipitang District, Sabah, East Malaysia (4°54’N 115°45’E, 748 m a.s.l.) .

Paratypes. Adult male FMNH 243936 collected by Robert F. Inger and Tan Fu Lian on 9 September 1990 from Purulon camp, Tenom District, Sabah, East Malaysia (5°13’N 115°57’E, 516 m a.s.l.). Adult male FMNH 249751 collected by Robert F. Inger on 6 December 1991 from Poring station, Mount Kinabalu Park, Ranau District, Sabah, East Malaysia (6°03’N 116°42’E, 606 m a.s.l.). Adult female FMNH 71590 collected by T. H. Harrisson in May 1952 from Pa Brayong, Lawas District, Sarawak, East Malaysia (estimated: 4.45°N 115.51667°E, 1,077m a.s.l.).

Referred specimens. Juvenile female MCZ R-178183 collected by L.H. Emmons on 7 September 1989 from Poring, Mount Kinabalu Park, Ranau District, Sabah, East Malaysia (6°03’06.4”N, 116°42’03.5”E, 575 m a.s.l.). Juvenile female FMNH248950/SP 04130 collected by Tan Fu Lian on 14 September 1991 from Tawau Hills, Tawau District, Sabah, East Malaysia (4°37’N 117°54’E, 266 m a.s.l.). Adult female ZRC 2.7348 collected by an unknown collector in the 1990s from Wind & Fairy Caves, Bau district, Sarawak, East Malaysia (estimated: 01°22.867 N, 110°07.164 E, 73 m a.s.l.).

Diagnosis. Asthenodipsas borneensis sp. nov. is diagnosed as member of the genus Asthenodipsas by its possession of smooth dorsals, absence of preoculars and suboculars, having supralabials in contact with the eyes, single anterior inframaxillary and two pairs of posterior inframaxillaries ( Grossmann & Tillack 2003). It can be separated from Aplopeltura boa (Boie) by its higher number of mid-dorsal scale rows (15 vs. 13) and subcaudals (divided vs. undivided) ( de Rooij 1917; Grossmann & Tillack 2003; Stuebing et al. 2014), and can be further differentiated from members of the genus Pareas by its possession of preocular and subocular scales (absent vs. present), supralabials in contact with orbit (3 rd & 4 th contact orbit vs. no supralabials in contact with orbit) and anterior single inframaxillary (present vs. absent) ( Grossmann & Tillack 2003). Asthenodipsas borneensis sp. nov. can be differentiated from its congeners by the following combination of characters: a maximum SVL of 441 mm; 15/15/15 dorsal scale rows; 166–179 ventrals; 35–48 subcaudal scales; two postoculars; 2(+0–1)+(1–3) temporals; seven or eight supralabials, 3 rd & 4 th touching the eye; 4–7 infralabials, 2 nd or 3 rd pair in contact; a sharp vertebral keel; dorsum of adults beige to orange-brown with a dark-brown to black patch on the neck followed by 23–40 irregularly-shaped, rhomboidal dark-brown bands that extend the length of body and tail and onto lateral edges of the ventral scales to form spots, but not encircling body; a narrow, light-coloured vertebral stripe starting from the nape or after the dark patch on the neck; throat and ventrals beige to yellow and mottled with small, dark spots except for neck region which is darkbrown to black, sometimes with a faint, light-coloured median stripe; head whitish to dark-grey with dark speckling on the snout, crown and labials; and iris reddish-brown and pupils black ( Table 1 , 2 & 7 ; Fig. 2 & 3 ).

Description of holotype. Adult female SVL 411 mm and Tal 55 mm; rostral slightly wider than tall; head bulbous, somewhat rectangular in shape, longer than wide (HL/HW 1.73); nasals undivided; internasals shorter than prefrontals; posterior margin of prefrontals contact eye; frontal hexagonal, slightly longer than wide; loreals present, longer than tall; supraoculars subpentagonal, approximately a quarter of both the length and width of frontal; preoculars absent; upper and lower postoculars present on both right and left sides of head, lower postocular extending to below orbit; suboculars absent; supralabials 7/7 with 3rd and 4th contacting orbit and 7th elongate; temporals 2(+1)+2/2+1, i.e. on left side of head there are two anterior temporals and two posterior temporals but between lower anterior and lower posterior temporal is an additional scale resulting in two upper temporals and three lower temporals, and on the right side of the head the upper anterior and posterior temporals are fused resulting in a single upper temporal and three lower temporals; mental triangular wider than long; anterior inframaxillary pentagonal, in contact with infralabials 1–3; two pairs of posterior inframaxillaries following anterior inframaxillary, both pairs of posterior inframaxillaries somewhat hexagonal, rhomboid-shaped, elongated; infralabials 5/5 with 3 rd pair in medial contact. Body long, stout, laterally compressed, bearing a prominent keel-shaped vertebral region; dorsal scales smooth, in 15/15/15 rows, vertebrals slightly enlarged; 179 ventrals; 38 divided subcaudals; cloacal scute entire; tail tapering to point.

Colouration in preservation ( Fig. 2A & B ). The ground colour of the head, body and tail are beige with very fine speckling. The speckling is lighter on the flanks and becomes heavier on the back closer to the vertebral scale rows. The top and underside of the head is lightly speckled and there are dark spots on the rostal, 1 st supralabials, 7 th supralabials along opening of the mouth, mental, inframaxillaries, and infralabials 1–3 along their medial sutures. On the neck is a dark patch starting from the nape, extending to approximately the position of the 20 th ventral. The dark patch starts as a narrow stripe on the 5 th & 6 th dorsal scale rows, gradually widens to dorsal scale rows 1–7, and does not extend cross the vertebral scales but completely encircles the ventrals. Starting behind the dark neck patch are 29 dark bands along the body that are somewhat rhomboidal to inverted-triangle in shape, and nine bands on the tail. The dark body bands range between 1–4 dorsal scales in length and are faint on the dorsum near the vertebral scale row and more prominent on the lower flanks and edges of the ventrals. The venter is beige and bears, dark lateral blotches from the extensions of the dorsal bands that meet the ventral scales as well as scattered dark spots the entire length of the body and tail. The thin vertebral stripe is cream.

Variation ( Fig. 2 & 3 ). The paratypes closely resemble the holotype in overall colour pattern and morphology. Paratypes FMNH 243936 and 249751 have more prominent banding on the body than the holotype ( Fig. 2C & E ). In FMNH 243936 the markings from the dark neck patch do not encircle the ventrals, leaving a narrow, light-coloured median stripe on the underside of the neck ( Fig. 2D ). Paratypes FMNH 71590 and 249751 also have chin and throat regions that are almost completely dark with only a few scattered light spots ( Fig 2F ). In life, the colouration of the head and body in this species is variable. The colouration of the head ranges from white with black mottling to dark-brown or grey, while the body ranges from beige to orange-brown ( Fig. 3 ). Juveniles are lighter coloured than the adults ( Fig. 3G & H ). Variation in scale counts and measurements within the type series and referred specimens are shown in Table 1 .

Comparison. Asthenodipsas borneensis sp. nov. can be differentiated from A. lasgalenensis Loredo, Wood, Quah, Shahrul, Greer, Ahmad & Grismer , A. tropidonotus (Lidth de Jude) and A. vertebralis (Boulenger) by its lower number subcaudals (35–48 vs. 54–77), pairs of infralabials in contact (3 rd vs. 1 st) and fewer pairs of posterior inframaxillaries (two vs. three). A. borneensis sp. nov. is distinguished from A. laevis by its larger adult length, (Max SVL 441 mm vs. 373 mm), dorsal scales rows (15/15/15 vs. 15/15/13) and sharp vertebral keel (present vs. absent). From A. jamilinaisi , A. borneensis sp. nov. can be differentiated by its lower number of subcaudals (35–48 vs. 52–53), higher number of supralabials (seven or eight vs. six [rarely seven]), size of vertebral scales (slightly enlarged vs greatly enlarged), body form (robust and bulky vs. gracile and laterally compressed), and colour pattern (beige to orange-brown dorsum with a dark neck patch followed by distinct dark bands and a usually lighter coloured head vs. dark overall colouration of dorsum with muted banding). From A. stuebingi to which it is superficially similar to, A. borneensis sp. nov. can be distinguished by its higher number of supralabials (seven or eight vs. six), smaller adult length (Max SVL 441 mm vs. 557 mm) and colour of iris (red vs. black) ( Quah et al. 2019). A. stuebingi is also an upland species known only from the highlands of Sabah, East Malaysia from 900–2000 m a.s.l. in elevation ( Quah et al. 2019) whereas A. borneensis sp. nov. ranges widely across Borneo ( Fig. 5 ) from the lowlands to approximately 1000 m a.s.l. in elevation ( Stuebing et al. 2014). Finally, from A. malaccana with which it was considered synonymous, A. borneensis sp. nov. can be differentiated by its larger adult length (max SVL = 441 mm vs. 365 mm), a significantly higher number of ventrals (166–179 vs. 152–169) and subcaudals (35–48 vs. 26–42), a sharp vertebral keel (present vs. absent) and colour pattern (beige to orange-brown dorsum with a dark neck patch followed by distinct dark bands and a usually lighter coloured head vs. dark-brown to black dorsum with a series of silver-grey to dirty-white blotches that form irregular cross bands across the back that start behind a broad dark area on the neck, and the colouration of the head ranging from whitish with dark spots to solid black) ( Figs. 2–4 ) ( Tables 1–4 & 7 ). An updated key to the family Pareidae of Borneo is presented below.

Distribution. Asthenodipsas borneensis sp. nov. ranges from as far west as Kuching, Sarawak to Tawau Hills, Sabah in the east ( Table 1 ; Fig. 3 & 5 ). Other reported localities for this species in East Malaysian Borneo are Crocker Range, Sabah ( Das 2006a), Bongon, Sabah and Mount Dulit, Sarawak (De Roij 1917; Stuebing 1991). In Kalimantan, it has been reported from Samarinda (De Roij 1917) and Bulungan Research Forest, Malinau ( Iskandar 2004). The species is expected to be more wide ranging in Borneo in the appropriate forest habitat.

Etymology. The specific epithet borneensis is in reference to its restriction to the island of Borneo. The suffix ensis is a Latin derivation meaning “from” or “inhabiting.” It renders the specific epithet an adjective that must be in grammatical accord with the gender of Asthenodipsas that is feminine (Frank Tillack in litt. 2019).

Natural History. Asthenodipsas borneensis sp. nov. has been recorded from lowland rainforests and montane regions up to elevations of 1000 m ( Malkmus et al. 2002; Stuebing et al. 2014). It is nocturnal and forages for snails on low vegetation at night. During the day it reportedly shelters beneath leaf litter ( Stuebing et al. 2014). The referred juvenile specimens MCZ R-178183 and FMNH248950/ SP 04130 were collected during the month of September but other juveniles have been photographed in the months of May (LSUDPC 10977) and November ( Fig. 3G & H ) indicating breeding may take place year round.

Figures

FIGURE 2. A. Dorsum of holotype of Asthenodipsas borneensis sp. nov. (FMNH 243935). B. Venter of holotype of A. borneensis sp. nov. (FMNH 243935). C. Dorsum of paratype of A. borneensis sp. nov. (FMNH 243936). D. Venter of paratype of A. borneensis sp. nov. (FMNH 243936). E. Dorsum of paratype of A. borneensis sp. nov. (FMNH 249751). F. Venter of paratype of A. borneensis sp. nov. (FMNH 249751).

FIGURE 3. Asthenodipsas borneensis sp. nov. from Borneo. A: Specimen from Kuching, Sarawak (LSUDPC 10988). B: Specimen from Sayap, Mount Kinabalu, Sabah (LSUDPC 10982). C – F (LSUDPC 10983–10986): Adults from Poring, Sabah. G & H (LSUDPC 10987 & 10978): Juvenile from Poring, Sabah. (Photographs by Chien C. Lee [A & B], Zhou Hang [C & D], Anton Sorokin [E & F] & Jaroslav Karhánek [G & H]).

FIGURE 5. Distribution of Asthenodipsas borneensis sp. nov. (red) and A. malaccana (blue). Star = type locality.