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Asthenodipsas borneensis QUAH, GRISMER, LIM, ANUAR & CHAN, 2020

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Higher TaxaPareidae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common NamesE: Bornean Dark-necked Slug Snake 
SynonymAsthenodipsas borneensis QUAH, GRISMER, LIM, ANUAR & CHAN 2020
Asthenodipsas malaccanus — CHAN-ARD et al. 2015: 159 (part)
Asthenodipsas malaccanus — CHARLTON 2020: 86–87 (part)
Asthenodipsas malaccanus — DAS 2006: 007 (part)
Asthenodipsas malaccanus — DAS 2010: 161 & 344–345 (part)
Asthenodipsas malaccanus — DAS 2012 & 2018: 131 (part)
Asthenodipsas malaccanus — ISKANDAR & COLIJN 2001: 111 (part)
Asthenodipsas malaccanus — MARLON 2014: 27–28 (part)
Asthenodipsas malaccanus — STUEBING et al. 2014: 87 (part)
Asthenodipsas malaccanus — TEYNIÉ et al. 2010: 39 (part)
Asthenodipsas malaccanus — WALLACH et al. 2014: 59 (part)
Amblycephalus malaccanus — BOULENGER 1892: 507 (part)
Amblycephalus malaccanus — BOULENGER 1896: 442–443 (part)
Amblycephalus malaccanus — BOULENGER 1912: 209–210 (part)
Amblycephalus malaccanus — FLOWER 1896: 896 (part)
Amblycephalus malaccanus — FLOWER 1899: 607 & 694 (part)
Amblycephalus malaccanus — DE ROOIJ 1917: 267–277 (part)
Internatus malaccanus — DAVID & VOGEL 1996: 137–138 (part)
Internatus malaccanus — MALKMUS et al. 2002: 343
Pareas malaccanus — DE HAAS 1950: 529 (part)
Pareas malaccanus — HAILE 1958: 766 (part)
Pareas malaccanus — GRANDISON 1972: 92 (part)
Pareas malaccanus — MARLON 2014: 27–28 (part)
Pareas malaccanus — STUEBING 1991: 331 (part)
Pareas malaccanus — STUEBING & INGER 1999: 88 (part)
Pareas malaccanus — TAYLOR 1965: 686 (part)
Pareas malaccanus — WELCH 1988: 90 (part)
Pareas carinatus — DAS 2006: 45
Pareas carinatus — DAS 2007: 161
Asthenodipsas (Asthenodipsas) borneensis — POYARKOV et al. 2022 
DistributionEast Malaysia (Borneo: Sabah)

Type locality: Mendolong camp watershed, Sipitang District, Sabah, East Malaysia (4°54’N 115°45’E, 748 m elevation).  
TypesHolotype. FMNH 243935, Adult female, collected by Robert F. Inger and Tan Fu Lian on 25 August 1990.
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.). 
DiagnosisDiagnosis: Asthenodipsas borneensis sp. nov. is diagnosed as member of the genus Asthenodipsas by its pos- session 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 (3rd & 4th contact orbit vs. no supralabials in contact with orbit) and anterior single inframaxil- lary (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, 3rd & 4th touching the eye; 4–7 infralabials, 2nd or 3rd 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 dark- brown 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 in Quah et al. 2020).

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 (3rd vs. 1st) 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 pat- tern (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 super- ficially 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. 
CommentActivity: nocturnal

Diet: snails

Habitat: lowland rainforests and montane regions up to elevations of 1000 m. During the day it reportedly shelters beneath leaf litter 
EtymologyThe 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). 
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