Ahaetulla isabellina (Wall, 1910) Mallik & Srikanthan & Pal & D’Souza & Shanker & Ganesh, 2020

Mallik, Ashok Kumar, Srikanthan, Achyuthan N., Pal, Saunak P., D’Souza, Princia Margaret, Shanker, Kartik & Ganesh, Sumaithangi Rajagopalan, 2020, Disentangling vines: a study of morphological crypsis and genetic divergence in vine snakes (Squamata: Colubridae: Ahaetulla) with the description of five new species from Peninsular India, Zootaxa 4874 (1), pp. 1-62 : 27-30

publication ID	https://doi.org/ 10.11646/zootaxa.4874.1.1
publication LSID	lsid:zoobank.org:pub:8FF98990-0E47-4BB7-82BB-098F86771271
DOI	https://doi.org/10.5281/zenodo.4567191
persistent identifier	https://treatment.plazi.org/id/353C523C-141D-2627-FF50-95C9FE85FD57
treatment provided by	Plazi
scientific name	Ahaetulla isabellina (Wall, 1910)
status	comb. nov.

Treatment

Ahaetulla isabellina (Wall, 1910) comb. nov.

Dryophis mycterizans isabellinus Wall, 1910

Ahaetulla nasutus (not of Lacépède, 1789)— Malhotra & Davis, 1991: 159

Neotype (designated herein). BNHS 3584 View Materials ( CESS182 ); adult female; Orukumaban range; Parambikulam; Coll. Ashok Kumar Mallik, 2011.

Neoparatype. BNHS 3585 (CESS164); adult male; Goodrickal range west, Periyar Tiger Reserve, Kerala; Coll. Saunak P. Pal, 2011.

CESS183; adult female; Oru komban range, Parambikulam; Coll. Ashok Kumar Mallik, 2011.

CESS167; adult male; Goodrickal range west, Periyar Tiger Reserve, Kerala; Coll. Saunak P. Pal, 2011.

CESS172; adult female; Goodrickal range west, Periyar Tiger Reserve, Kerala; Coll. Saunak P. Pal, 2011.

CESS262; adult female; Achankovil / Devarmalai, Agasthyamalai, Kerala; Coll. Saunak P. Pal, 2011.

CESS329; adult male; Kakki; Coll. S.R. Chandramouli, 2012.

CESS404; adult female; Idukki Wildlife Sanctuary, Kerala; Coll. S.R. Chandramouli, 2012.

Type locality. Paralai, Valparai (10.335 N, 76.952 E, 1100 msl; original type locality); by virtue of present neotypification: GoogleMaps Oru Komban hills (10.4077 N, 76.7177 E, 1077 msl), in Parambikulam plateau of Anaimalai Hill complex, Southern Western Ghats, Peninsular India GoogleMaps .

Etymology. Named in allusion to the isabelline yellow colouration of the dorsal body of the original name-bearing type in live condition (see Wall 1910).

Remarks. Wall (1910) erected the subspecific nomen Dryophis mycterizans isabellinus based on a brown-coloured adult female holotype (by monotypy) collected from Paralai, Valparai in the Anaimalai Hills of the Southern Western Ghats. The original description states the colour of this new nominate subspecies to be “uniformly buff or khaki above and a similar colour only of a lighter shade on the belly between the two lateral stripes and ventrals and subcaudals were 168+136.” When Wall (1910) erected this nomen, his intent to diagnose this variety from the nominotypical, i.e., green ones, was its brownish dorsal colour. He had described it along with other new “brownish” varieties of what was then known as Dryophis mycterizans . The museum registration number of the holotype stands unknown (Wall 1910; Das & Chaturvedi 1998) and the type appears to be untraceable from other A. nasuta complex specimens lodged with the Bombay Museum ( Das & Chaturvedi 1998).

Since its inception in 1910, this trinomial has never been deployed as a species-series nomen, that is recognised as a species (see Wallach et al. 2014), for over a century ( Uetz et al. 2019). Contrarily, this trinomial has been relegated to the synonymy of the “green” A. nasuta multiple times by multiple authors (e.g. Taylor 1965; Wallach et al. 2014). Other nominate taxa, including those erected both before and after the erection by Wall (1910), alluding to the “brown” forms have also been relegated to the synonymy of the “green” A. nasuta - Coluber russellianus Bell, 1825 , Dryinus fuscus Duméril, Bibron & Duméril, 1854 and Dryophis mycterizans rhodonotus Wall, 1921 (see Boulenger 1890, 1896; Taylor 1965; Wallach et al. 2014). This is despite the fact that the former two were originally described as species-series nomina and not as trinomials for denoting “varieties”. Later usages of this nomen, Ahaetulla nasuta isabellinus (Wall, 1910) , by Whitaker & Captain (2004) [from Pune], Rao et al. (2005) [from Srisailam] and Deepak et al. (2019) [from Tirunelveli and Madras] were not only distant from typical locality, but were also represented with a cf. prefix, denoting taxonomic uncertainty.

Based on the integrated taxonomic revisions of Ahaetulla by us as well as other authors, it appears that colour polymorphism is marked in this genus, with females tending to be brownish in many groups (see Whitaker & Captain 2004; David & Dubois 2005; Ganesh & Chandramouli 2011; Mohapatra et al. 2017; this work, see A. malabarica sp. nov.). Adding to this, there have been reports of A. nasuta spp. with a brownish body and greenish head ( Varma & Gharat 2019). It is also to be acknowledged that A. pulverulenta and A. laudankia are two congeners that are never green, but always brownish (see Deepak et al., 2019), indicating that it is not implausible that A. isabellina is also such a taxon. However, only two congeners inhabit Anaimalai, that are either always or often brownish— A. sahyadrensis (formerly A. pulverulenta , in part) and A. dispar respectively ( Whitaker & Captain 2004). Neither of these recognized taxa have been associated with the nomen Dryophis mycterizans isabellinus (see synonymies in Wallach et al. 2014).

Therefore, as the holotype of this nominate taxon is untraceable (see Das & Chaturvedi 1998; ANS pers. obs.), and this nominate taxon is in need of revision ( Deepak et al. 2019; this work), in accordance with Art.75.3 of the Code (ICZN 1999), we hereby designate BNHS 3584 (ex. CESS182) as the neotype of the nomen Dryophis nasutus isabellinus Wall, 1910 . The neotype comes from a locality (Parambikulam) close (<30 km) to the original type locality (Valparai), is also a female, and represents a population that has scale counts within the range given in original description (Ventrals 167–183, Subcaudals 105–149 vs. Ventrals 168, Subcaudals 136 in Wall 1910), although it does not agree with the original description and is green in colour.

Diagnosis.

1. Ahaetulla isabellina comb. nov. (L5) is phylogenetically part of a clade consisting of three other new lin-eages (L3, L4 & L6) from the Western Ghats and L2 from Sri Lanka (>70%). It is closely related to another new species A. farnsworthi sp. nov. (L4).

2. Ahaetulla isabellina comb. nov. and A. farnsworthi sp. nov. maintain low genetic divergence of 3.4% (in ND4) 3.5% (in Cytb) and 1.1% (in 16S) from each other.

3. A species of Ahaetulla having short rostral appendage (vs. long in A. oxyrhyncha comb. nov.; A. anomala , A. laudankia ), possessing a white ventrolateral stripe (vs. absent in A. pulverulenta , A. sahyadrensis nom. nov.); absence of a loreal scale (vs. present in A. dispar and A. travancorica sp. nov.); 7 pre-diastemal and 9 post-diastemal maxillary teeth (vs. 6 and 7 in A. malabarica sp. nov., vs. 6 and 11 in A. farnsworthi sp. nov.,vs. 6 and 8 in A. borealis sp. nov., vs. 7 and 7 in A. oxyrhyncha comb. nov.); we have not found any further morphological difference from other closely related lineages ( A. malabarica sp. nov., A. farnsworthi sp. nov., and A. borealis sp. nov.) ( Fig. 3 View FIGURE 3 & 13 View FIGURE 13 , Table 2 View TABLE 2 ).

4. Ahaetulla isabellina comb. nov. is distributed in the Southern Western Ghats separated from other (the northern and Central Western Ghats) populations by the Palghat Gap. Currently, we have found that the distribution ranges from Parambikulam to the Devarmalai hills and the actual distribution range will need to be established with more sampling in the future.

Description of Neotype. Adult female of total length 1020 mm; dissected; very slender, partially laterally compressed body with snout to vent length 640 mm; tail length 380 mm; relative tail length 0.38; ventrals 182 notched with keels; subcaudals 148, divided; cloacal scale divided; relatively long and slender tail; dorsal scale rows in 15- 15-13 rows of smooth, obliquely disposed scales; head very distinct from neck with head length 33 mm; transversely oval eyes with horizontal pupil, with a horizontal diameter of 4.8 mm and vertical diameter of 3.45 mm; distance from nostril to eye 7.2 mm; distance from snout tip to eye 10.8 mm; supralabials 8 (both left and right) with the 5 th supralabial being the largest, in contact with the eye; 4 th supralabial divided; infralabials 9 (both left and right); 1 st, 2 nd, 3 rd and 4 th infralabials in contact with anterior genials; 4 th and 5 th infralabials in contact with the posterior genials; mental scale wedged in between 1 st pair of infralabials not in contact with the genials; nasal scale 1 (both left and right); loreals absent; pre-suboculars 2 (both left and right); pre-ocular 1 (both left and right); post-oculars 2 in the right and 3 in the left; sub-oculars absent; temporals 1+2+2 (both left and right); prefrontal scale in contact with the pre-oculars; preventral 1; rostral appendage with 2 scales.

Hemipenis (dissected from CESS167). Organ fairly short (5.2 mm long) and of medium width (4.7 mm wide); extending upto 1.5 to 2 subcaudal scales; unilobed, lobe head wide (5 mm), pedicel covered by cursive flounces; flounces appear clumped and sticking onto one another in clusters, probably a preservation artefact; length of largest spine 0.6 mm; spines appear cramped except the short spiky ones on top; those on the sides curved and clumped; in asulcate view, spiny flounces fully cover the entire length of the pedicel, no plain smooth patch visible; in sulcate view, sulcus spermaticus mildly visible, apparently centripetal, turning to the right.

Maxillary arch dentition (dissected from CESS182). Arched with a dip in the arch towards the diastema; 16 teeth perpendicular to maxilla, curving inwards; pre-diastemal teeth 7; post-diastemal teeth 9, observable gradual tooth size increase in prediastemal tooth set with the largest teeth precursing the diastema; diastema about 4 toothsockets wide; suffixed with a set of 7 smaller teeth followed by the last grooved pair of large teeth ( Fig. 6b View FIGURE 6 ).

Colour in life. Body uniform bright green; infralabials and venter yellowish-green to light green at mid body; yellow ventral stripe along notched ventral keels; slight discolouration in the pre-ocular; inter-scalar skin patterned with black and white anteriorly-converging bars revealing when threatened; hindbody inter-scalar skin reddish instead of white; golden yellow eyes with black speckles; concentration of black speckles both in the anterior and posterior ends of a horizontal pupil and a slight discolouration around the pupil; tail and subcaudals green.

Colour in preservative. Body non-uniform bluish green to light blue in colour; rostral, infralabials and ventral white; white ventral stripe along the notched ventral keels; slight discolouration in the pre-ocular; interstitial skin coloured with a consecutive series of black and white bars that converge towards the head; yellow clouded with white eyes with black speckles; concentration of black speckles both in the anterior and posterior ends of a dilated pupil.

Variations shown by Neoparatype. In general, agreeing with the neotype and showing the following intraspecific variations: Ventrals 167–183 notched with keels; subcaudals (males) 159–167 divided and subcaudals (females) 105–149 divided; scale rows around the body in 15-15–13/11 rows of smooth, obliquely disposed scales; supralabials 8–9 with either 5 th, 6 th or 7 th supralabial being the largest; either 5 th or 6 th in contact with the eye; supralabial scale division on the 4 th SL; infralabials 8–9; pre-suboculars 1 or 2; pre-ocular 1 (both left and right); postoculars 1 or 2; sub-oculars absent; temporals 1+2 or 2+2. Some specimens have a pronounced rostral appendage with scale divisions (1–2).

Body bright green with blue obscure patches; a gradual reduction of blue patches from venter to dorsum; body in some specimens uniform olive to light brown; more prominent along sides; rostral, infralabials and the midbody along venter light green to light blue; sometimes a yellow ventral stripe along the notched ventral keels; inter-scalar skin white with black and white anteriorly-converging bars along forebody, becoming reddish along hindbody; eye from yellow to orange with light brown marbled patterns; horizontal pupil with a light blue or yellow colouration around pupil; tail, subcaudals green.

Distribution and Habitat. This species is found in the Southern Western Ghats, south of the Palghat Gap, starting from the Anamalai hills extending southwards to the Sivagiri hills, at elevations from ~ 550 m to 1475 msl ( Fig. 4 View FIGURE 4 & 14 View FIGURE 14 ), predominantly in evergreen rainforests. More work is needed to determine the southern limit of its distribution range.