Key to the slug snakes of the family Pareidae of Borneo 1. Subcaudal scales paired, 15 dorsal scale rows at mid-body.................................................... 2 - Subcaudal scales in a single row, 13 dorsal scale rows at mid-body, head distinctly wider than neck, diameter of eye larger than distance to nostril......................................................................... Aplopeltura boa 2. Preoculars & suboculars present, two shields (loreal & preocular) between nasal and eye, supralabials not touching the eye (separated by suboculars)............................................................................... 3 - Preoculars & suboculars absent, single shield (loreal) between nasal and eye, one or more supralabials in contact with the eye ................................................................................................... 4 3. Ventrals 195–218, subcaudals 105–118, large dark marking on nape that reaches far down on the side of the neck................................................................................................. Pareas nuchalis - Ventrals 161–189, subcaudals 53–99, X-shaped mark on the top of the neck.......................... Pareas carinatus 4. Either 1 st or 3 rd pair of infralabials in contact................................................................ 5 - 1 st and 3 rd pairs of infralabials in contact, two pairs of posterior inframaxillaries, supralabials 3–5 (rarely 3 & 4) in contact with orbit......................................................................... Asthenodipsas ingeri sp. nov. 5. 3 rd (rarely 2 nd) pair of infralabials in contact................................................................. 6 - 1 st pair of infralabials in contact, three pairs of posterior inframaxillaries, adult colouration brown with dark cross-bands, an interrupted yellow or orange vertebral line, labials and chin-shields yellowish, edged with dark-brown, venter yellowish, with some brown spots on the sides....................................................... Asthenodipsas vertebralis 6. Five to six supralabials................................................................................. 7 - Seven to eight supralabials, long black saddle on neck nearly encircling the body............... Asthenodipsas borneensis 7. Dorsal scale rows 15/15/15, sharp vertebral keel present...................................................... 8 - Dorsal scale rows 15/15/13, sharp vertebral keel absent, 148–173 ventrals........................ Ashtenodipsas laevis 8. Subcaudals 35–47, ventrals in males 165, dorsum light-brown with a dark neck patch and distinct bands, body robust and stout............................................................................. Asthenodipsas stuebingi - Subcaudals 52–53, ventrals in males 173–175, dorsum dark overall with indistinct banding, body gracile and laterally compressed......................................................................... Asthenodipsas jamilinaisi

Published as part of Quah, Evan S. H., Lim, Kelvin K. P. & Grismer, L. Lee, 2021, On the taxonomic status of Asthenodipsas vertebralis (Boulenger, 1900) (Squamata Pareidae) in Borneo with the description of a new species, pp. 24-44 in Zootaxa 4949 (1) on pages 40-41, DOI: 10.11646/zootaxa.4949.1.2, http://zenodo.org/record/4677338