Asthenodipsas ingeri, Quah, Evan S. H., Lim, Kelvin K. P. & Grismer, L. Lee, 2021

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, Zootaxa 4949 (1), pp. 24-44 : 28-32

Asthenodipsas ingeri sp. nov.

Inger’s Slug Snake

( Figs. 2 , 4 & 5 ; Tables 2–4 )

urn:lsid:zoobank.org:act:BC8DA9CE-2C05-4D07-B1BE-24A30CAF908A

Amblycephalus vertebralis: Loveridge 1938: 43

Asthenodipsas vertebralis (in part): Stuebing et al. 2014: 82 & 86.

Pareas vertebralis (in part): Cox et al. 1998: 79; de Haas 1950: 529; Haile 1958: 759, 766; Iskandar & Colijn “2001” 2002: 113; Manthey & Grossmann 1997: 308, 378; Stuebing 1991: 331; Stuebing & Inger 1999: 87; Inger & Voris 2001: 890.

Amblycephalus laevis (in part): Smith 1925: 20.

Asthenodipsas laevis (in part): Grossmann & Tillack 2003: 180; Stuebing et al. 2014: 82.

Internatus laevis (in part): Malkmus et al. 2002: 342.

Pareas laevis (in part): Stuebing & Inger 1999: 87.

Pareas carinatus (in part): Das 2012: 132; 2018: 132.

Holotype. Adult female MCZ R 43592, collected by John A. Griswold Jr. in July 1937 from Lumu Lumu , Mount Kinabalu, Sabah, East Malaysia (estimated: N 6.01966, E 116.539501, 1728 m a.s.l.).

Diagnosis. Asthenodipsas ingeri sp. nov. can be differentiated from its congeners by the following combination of characters: a maximum SVL of 715 mm; 15/15/15 dorsal scale rows; 201 ventrals; 53 subcaudal scales; one or two postoculars; 2+2+2 temporals; seven supralabials, 3 rd,4 th & 5 th (sometimes 3 rd & 4 th) touching the eye; six to seven infralabials, 1 st and 3 rd pair in contact; single anterior inframaxillary present; two pairs of posterior inframaxillaries; a sharp vertebral keel; dorsum of adults brown to grey and overlain with up to 51 irregularly-shaped, rhomboidal dark-brown bands beginning on the nape and extending the length of body and tail and onto the lateral edges of the ventral scales to form spots, but not encircling body; a narrow, light-coloured vertebral stripe; throat and ventrals white to cream-coloured with very fine speckling; top of head and snout darker than ground colouration of body while the supralabials and temporal region are lighter in colour; and iris and pupils black ( Table 2 & 3 ; Fig. 2 , 4 & 5 ).

Description of the holotype ( Table 2 ). Adult female, SVL 715 mm and TaL 103 mm; rostral approximately as wide as it is high; head bulbous, longer than wide (HL/HW 1.47); nasals undivided; internasals shorter than prefrontals; posterior margin of prefrontals contact eye; frontal hexagonal, approximately equal in length and width; loreals present, longer than tall; supraoculars subpentagonal, approximately half the length and half the width of frontal; preoculars absent; upper and lower postoculars present on both left and right side, lower postocular extending to slightly below orbit; suboculars absent; supralabials 7/7 with 3 rd, 4 th & 5 th contacting orbit and 7th elongate; temporals 2+2+2/2+2+2 ( Fig. 4A ); mental triangular, wider than long; anterior inframaxillary pentagonal, in contact with infralabials 1–3; two pairs of posterior inframaxillaries following anterior inframaxillary, first pair of posterior inframaxillaries slightly oval, rhomboid-shaped, second pair more hexagonal, elongated; infralabials 6/7 with 1 st and 3 rd pair in medial contact ( Fig. 5A ). Body long, bulky, laterally compressed, bearing a prominent keel-shaped vertebral region; dorsal scales smooth, in 15/15/15 rows, vertebrals enlarged; 201 ventrals; 53 divided subcaudals; cloacal scute entire; and tail tapering to a point.

Colouration in preservation ( Fig 2A & B ). The ground colour of the head, body and tail is beige with dark speckling. The speckling is heavier on the top of the head, snout and around the orbits on the prefrontals, loreal, supraocular, postoculars, and upper corners of supralabials 3–6. The mental, inframaxillaries, infralabials and preventrals are heavily speckled. Beginning on the nape are approximately 51 very faded, rhomboidal bands ranging from 1–3 dorsal scales in length and running along the dorsum to the base of the tail. The tail is mottled with dark spots and markings. The venter is cream-coloured with dark speckling along the lateral edges. Faded spots occur along the lateral edges of the venter where the dorsal bands meet the ventral scales. The thin vertebral stripe is cream-coloured.

Variation. Based on photographs of other specimens from Mount Kinabalu, Sabah ( Fig. 2C–E ) and Payeh Maga Highlands, Sarawak ( Fig. 2F ) that are tentatively identified here as A. ingeri sp. nov. the dorsal ground colour in life ranges from beige to light-grey with more prominent dark banding on the body and the venter ranges from white to cream-coloured. Most of the photographed specimens (LSUDPC 12632–12635) approach the holotype in having supralabials 3–5 in contact with the orbit ( Fig. 4A–C ) but one specimen (LSUDPC 12636) appears to have a division of the 5 th supralabial (it may also be the division of the lower postocular that extends to below orbit) which leaves only the 3 rd and 4th supralabials contacting the orbit ( Fig. 4D ). However, this specimen resembles the holotype in having contact between the 1 st and 3 rd pairs of infralabials which tentatively identifies it as A. ingeri sp. nov. ( Fig. 5B ). Scale counts based off digital images also found this specimen to have approximately 185 ventrals and 56/57 subcaudals (Bj ӧrn Lardner in litt. 2021).

Comparison ( Table 4 ). Asthenodipsas ingeri sp. nov. can be differentiated from A. laevis , A. borneensis , A. malaccana , A. jamilinaisi and A. stuebingi by its higher number of ventrals (185–201 vs. 148–179) and the pairs of infralabials in contact (1 st & 3 rd vs. 2 nd or 3 rd). It can be further separated from A. laevis by its number of dorsal scale rows (15/15/15 vs. 15/15/13) and the sharp vertebral keel (present vs. absent) ( Quah et al. 2019, 2020). From A. vertebralis , A. tropidonotus and A. lasgalenensis , the new species can be distinguished by the pairs of infralabials in contact (1 st & 3 rd vs. 1 st) and fewer pairs of posterior inframaxillaries (two vs three) ( Fig. 5 ). Asthenodipsas ingeri sp. nov. can be further distinguished from A. vertebralis , A. tropidonotus and A. lasgalenensis by the number of supralabials in contact with the orbit (3–5 [rarely 3 & 4] vs. 3 & 4 [rarely 3–5 or only 3 or 4]) ( Fig. 4 & 6B ), and having fewer subcaudals (53–57 vs. 57–79). In addition, A. ingeri sp. nov. can be further distinguished from A. tropidonotus by its higher number of postoculars (2 vs. 1), and from A. lasgalenensis by its dorsal colouration in adults (light-brown with dark bands and prominent vertebral stripe vs. solid dark-brown to black and no vertebral stripe) ( Fig. 6 ). In life A. ingeri sp. nov. can also be distinguished from A. vertebralis , A. lasgalenensis and A. tropidonotus (https://www.inaturalist.org/observations/10935163) by the colouration of its iris (dark brown vs. orange to reddish-brown) ( Fig. 2C–F , 4B–D & 6 ) ( Table 3 ; Loredo et al. 2013; iNaturalist). A key to the slug snakes of Borneo is presented below.

Etymology. The specific epithet ingeri is in honour of Robert F. Inger (10 September 1920 – 12 April 2019) for his extensive work on the reptiles and amphibians of Borneo and his overall contributions to the field of herpetology throughout Asia for nearly 80 years.

Distribution ( Fig. 7 ). Asthenodipsas ingeri sp. nov. is presently only confirmed from Mount Kinabalu in Sabah, East Malaysia, and may possibly occur in the Payeh Maga Highlands, Sarawak, East Malaysia based on a photograph of a specimen tentatively identified as this species ( Fig. 2F & 4B ).

Natural history. Very little is known about the natural history of Asthenodipsas ingeri sp. nov. except that it is a nocturnal, upland species ranging from 1,000 –2,000 m a.s.l. in elevation. Observers who photographed specimens tentatively identified as this species ( Fig. 2C–F & 6A ) have reported observing the snakes crawling through low vegetation at night. Based on its similarities to other species of Asthenodipsas , it is expected to be a semi-arboreal species found in montane forest where it feeds on snails ( Grismer 2011; Loredo et al. 2013).

Figures

FIGURE 2. A & B. Dorsum and venter of holotype of Asthenodipsas ingeri sp. nov. (MCZ R43592) from Lumu Lumu, Mount Kinabalu, Sabah. C, D & E. Adults of A. ingeri sp. nov. from Kinabalu National Park, Sabah, (LSUDPC 12634, 12632 & 12636 respectively). F. Adult Asthenodipsas cf. ingeri sp. nov. (LSUDPC 12633) from Payeh Maga Highlands, Sarawak. (Photographs by Evan Quah [A–B], Jannico Kelk [C], Kurt H.P. Guek [D], Björn Lardner [E], & Chien C. Lee [F]).

FIGURE 4. Arrangement of supralabials in: A. Holotype of Asthenodipsas ingeri sp. nov. (MCZ R43592) from Lumu Lumu, Mount Kinabalu, Sabah. B. Adult Asthenodipsas cf. ingeri sp. nov. (LSUDPC 12633) from Payeh Maga Highlands, Sarawak. C & D. Adults of A. ingeri sp. nov. from Kinabalu National Park, Sabah (LSUDPC 12634 & 12636 respectively). E. Adult A. vertebralis (LSUHC 11709) from Bukit Larut, Perak. F. Asthenodipsas vertebralis (ZRC 2.6619) from Gunung Berumput, Sarawak. Figures not to scale. (Photographs by Evan Quah [A & E], Chien C. Lee [B], Jannico Kelk [C], Björn Lardner [D], & Kelvin K.P. Lim [F]).

FIGURE 5. Arrangement of scales on the underside of head in: A. Holotype of Asthenodipsas ingeri sp. nov. (MCZ R43592) from Lumu Lumu, Mount Kinabalu, Sabah. B. Adult Asthenodipsas ingeri sp. nov. (LSUDPC 12636) from Kinabalu National Park, Sabah. C. Asthenodipsas vertebralis (ZRC 2.6619) from Gunung Berumput, Sarawak. D. Adult A. vertebralis (LSUHC 12758) from Genting Highlands, Pahang. Figures not to scale. IL = infralabials, M = mental, SaIM = single anterior inframaxillary, pIM = pairs of posterior inframaxillaries. (Photographs by Evan Quah [A & D], Björn Lardner [B], & Kelvin K.P. Lim [C]).

FIGURE 6. A & B. Asthenodipsas ingeri sp. nov. (LSUDPC 12635) from Kinabalu National Park, Sabah, Borneo. C. Topotypic specimen of A. vertebralis (LSUHC 11709) from Bukit Larut, Perak, Peninsular Malaysia. D. Uncollected topotypic specimen of A. lasgalenensis from Bukit Larut, Perak, Peninsular Malaysia. (Photographs by Chien C. Lee [A & B] and Evan Quah [C & D]).

FIGURE 7. Distribution of Asthenodipsas ingeri sp. nov. (blue star), A. cf. ingeri sp. nov. (blue circle) and A. vertebralis (red circle) in Borneo. Star = type locality.