Ahaetulla oxyrhyncha ( Bell, 1825 ) Mallik & Srikanthan & Pal & D’Souza & Shanker & Ganesh, 2020
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publication ID |
https://doi.org/ 10.11646/zootaxa.4874.1.1 |
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publication LSID |
lsid:zoobank.org:pub:8FF98990-0E47-4BB7-82BB-098F86771271 |
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DOI |
https://doi.org/10.5281/zenodo.4564527 |
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persistent identifier |
https://treatment.plazi.org/id/353C523C-1415-262F-FF50-95C9FCD4FEBB |
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Plazi |
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scientific name |
Ahaetulla oxyrhyncha ( Bell, 1825 ) |
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comb. nov. |
Ahaetulla oxyrhyncha ( Bell, 1825) comb. nov.
Dryinus oxyrhynchus Bell, 1825
Dryinus russellianus Bell, 1825
Dryophis passericki Schinz, 1833
Dryinus rostratus Schinz, 1833
Type material. Syntypes, including the specimen depicted in Plate XII in Russell 1796, vol. I (see Bell 1825; Bauer 2015; Bauer et al. 2015).
Type locality. ‘Indes Orientalis’.
Etymology. Latin, alluding to the pointed rostral scale; oxyus = sharp, rhynchus = of the nose / snout, literally meaning sharp-snouted.
Comments. As Bell (1825: 326) first erected the name Dryinus oxyrhynchus , and in the next page (i.e p. 327) the name D. russellianus , according to ‘position precedence’ as per Rec. 69A.10 of ICZN, 1999, oxyrhynchus is conferred on this population. Specific epithet emended according to Art. 31.2 of ICZN, 1999.
Referred Material. CESS211 ; Adult female; NCBS campus (13.071 N 77.579 E; 780 m AMSL) GoogleMaps , Bangalore, Karnataka; Coll. Ashok Kumar Mallik, 2011 .
Diagnosis (redefined herein).
1. Ahaetulla oxyrhyncha ( Bell, 1825) comb. nov. (L1) is nested within a well supported (>70 %) clade com-prising A. sahyadrensis nom. nov. (L7), A. anomala and A. pulverulenta (L8). In addition, A. sahyadrensis nom. nov. shares ancestry with the clade comprising Ahaetulla oxyrhyncha ( Bell, 1825) comb. nov. and A. anomala.
2. There is a low genetic divergence between Ahaetulla oxyrhyncha ( Bell, 1825) comb. nov. and A. sahya-drensis nom. nov., which was also observed in other interspecific clades (eg. between lineage L4 & L5). The genetic divergence between Ahaetulla oxyrhyncha ( Bell, 1825) comb. nov., “ A. nasuta cf. isabellina ” Deepak et al. 2019, A. anomala and Ahaetulla sp. (CESS521 & CESS528) was also very low (1.6–2.5 % in Cytb vs <3 %; and 0.6–1.1 % in 16S vs <1 %). However, there is clear morphological differentiation despite a low level of genetic divergence between these closely related species.
3. This is a species of Ahaetulla with a long rostral appendage (vs. with short rostral appendage in A. isabel-lina comb. nov., A. malabarica sp. nov., A. farnsworthi sp. nov., A. borealis sp. nov.; vs. no rostral ap-pendage in A. dispar , A. travancorica sp. nov. and A. perroteti ), lacking loreal scale (present in A. dispar ), having usually green body colouration (vs. usually grey-brown in A. pulverulenta , A. sahyadrensis nom. nov., adult females often brown in A. anomala ), possessing a white or yellow ventrolateral stripe (vs. absent in A. pulverulenta , A. sahyadrensis nom. nov.); lacking any crown markings (vs. a distinct rhomboid crown marking present on top of the head in A. sahyadrensis nom. nov. and A. anomala ); with a rostral append-age composed of a grooved elongate scale (vs. rostral appendage composed of multiple small scales in A. pulverulenta, A. sahyadrensis nom. nov. and A. anomala ) ( Table 2 View TABLE 2 ).
4. Geographically, Ahaetulla oxyrhyncha ( Bell, 1825) comb. nov. is distributed in the lowland and drier habi-tats of Peninsular India, isolated from other members of Ahaetulla from the Western Ghats and wetzone of Sri Lanka ( Fig. 4 View FIGURE 4 ). It is geographically separated from the Western Ghats taxa (L3–L6 and A. sahyadrensis nom. nov.) that have a preference for wet zone regions. Moreover, even our sparse sampling from different sampling localities indicates that there was a lower impact of geographic barriers on the genetic structure of these widely distributed populations of Ahaetulla oxyrhyncha ( Bell, 1825) comb. nov.
Description of referred material. Adult of total length 1545 mm; slender, partially laterally compressed body with snout to vent length 920 mm; tail length 625 mm; relative tail length 0.40; ventrals 170 notched with keels; subcaudals 145, 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 50.2 mm; transversely oval eyes with horizontal pupil, with a horizontal diameter of 4.6 mm and vertical diameter of 2.9 mm; distance from nostril to eye 11.7 mm; distance from snout tip to eye 19.4 mm; supralabials 8 on right, 9 on left with 6 th (Right) and 7 th (Left) supralabial being the largest, 5 th (Right), 7 th (Left) supralabial 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 posterior genials; nasal scale (both left and right); loreals absent; pre-suboculars 2 (both left and right); pre-ocular 1 (both left and right); post-oculars 2; sub-oculars absent; temporal 1+3+2 on left and 2+2+2 on right; prefrontal scale in contact with pre-oculars; preventral 1.
Colour in life. Dorsum uniform grass green; rostral, infralabials, venter yellowish green to light green at mid body; yellow ventral stripe along ventral; slight discolouration in the pre-ocular; inter-scalar skin with black and white anteriorly-converging bars; golden yellow eyes with black speckles; concentration of black speckles both in anterior and posterior ends of a horizontal pupil; slight discolouration around the pupil; tail, subcaudals green ( Fig. 10 View FIGURE 10 a–f).
Colour in preservative. Dorsum uniform bluish green colour; rostral, infralabials, venter light blue; white ventral stripe along ventral; slight discolouration in the pre-ocular; inter-scalar skin creamy white with black and white anteriorly-converging bars; eyes yellow clouded with white and black speckles; concentration of black speckles both in the anterior and posterior ends of a dilated pupil.
Variations within other material. This highly variable species shows the following intraspecific variations (see also Mohapatra et al. 2017): ventrals 170–189; subcaudals (males) 142–167 divided, (females) 144–174 divided; dorsal scale rows in 15-15–13/11 rows of smooth, obliquely disposed scales; supralabials 8–10 with 5 th or 6 th supralabial being the largest; 5 th or 6 th supralabial in contact with the eye; 4 th supralabial divided; loreal absent, infralabials 8–10; pre-suboculars 2; pre-ocular 1 (both left and right); post-oculars 2; sub-oculars absent; temporal 1+2 or 2+2; rostral appendage usually comprised of 1–2 scales.
Maxillary arch dentition (dissected from CESS211). Arched with a dip towards diastema; 14 teeth perpendicular to maxilla, curving inwards; prediastemal teeth 7, postdiastemal teeth 7, observable gradual tooth size increase in prediastemal tooth set with the largest teeth precursing diastema; diastema smaller, 3 tooth-sockets wide, suffixed with a set of 5 uniform, smaller teeth followed by the last grooved pair of large teeth ( Fig. 6f View FIGURE 6 ).
Variations in colour morphs. Apart from the aforementioned colour form, other colour forms are restricted to smaller subpopulations from Ramnad and northern Odisha. The Ramnad and other south Indian subpopulations have a body with a uniform bright green colour; infralabials and mentum light green to white separated by a posterior eye stripe that is light yellow to yellowish green; venter white to reddish brown towards midbody; some infralabials with small blue patches; white ventral stripe along ventrals from a few scale rows after nape; slight discolouration in the pre-ocular; inter-scalar skin white with black and white anteriorly-converging bars; eyes golden yellow with black speckles; concentration of black speckles both in the anterior and posterior ends of horizontal pupils and a slight discolouration around the pupil; tail, subcaudals green.
Distribution and habitat. Ahaetulla oxyrhyncha ( Bell, 1825) comb. nov. is distributed throughout Peninsular India excluding the wet forest habitats of the Western Ghats ( Whitaker & Captain 2004) ( Fig. 4a View FIGURE 4 ). This species may also occur in the far northern dry zone of Sri Lanka. Our sampling indicates that this species is distributed in lowland areas near the coast on the western side of the Western Ghats, the southern tip of Peninsular India and drier parts of Karnataka. While considering the range of A. anomala ( Mohapatra et al. 2017) , the range of A. oxyrhyncha comb. nov. extends further into the central and east coast of Peninsular India including Odisha and West Bengal. Mostly found in arid and semi-arid habitats in dry deciduous forests, open habitats including scrub forests, coastal forests, and in Indian savannah. We did not find this species during our extensive sampling within the Western Ghats.
Remarks on Ahaetulla anomala ( Annandale, 1906) . Annandale (1906) described a subspecies of vine snake from Santragachi, in Bengal as Dryophis mycterizans anomalus . Subsequently, Mohapatra et al. (2017) worked on this form and recognized it as a distinct species A. anomala ( Annandale, 1906) , based on morphological and molecular data. When their work was underway, there was no clarity on the definition of the widespread Ahaetulla sp. that has now been conferred the nomen A. oxyrhyncha . Thus, owing to an incomplete prevailing understanding of the typical form, Mohapatra et al. (2017) fell short of clarifying the distribution and relationships within this group as a whole. It can be inferred from our phylogenetic tree that the large geographic distance and morphological variation do not reflect in the genetic structure of these distant and dissimilar populations of A. anomala and A. oxyrhyncha comb. nov. This did not feature in the work of Mohapatra et al. (2017). In spite of its geographically circumscribed morphological variation ( Mohapatra et al. 2017), its genetic divergence from its sister lineage is lower (1.7–2.5 % in Cytb & 0.0–1.1 % in 16S) than the lowest interspecific divergence values that we use to define species in our work (eg. 3.5 % in Cytb & 1.1 % in 16S between lineages L4–L5).
This is an example of morphologically distinct geographically restricted species with low genetic divergence. Since our study was focused on the Western Ghats and does not involve a wide sampling of the A. oxyrhyncha group from other ecoregions of the Peninsular India, we provisionally maintain the status quo regarding the taxonomy of Ahaetulla anomala , as defined by Mohapatra et al. (2017). Further inputs are needed to resolve this particular group, involving a widespread sampling of several of the nominate forms belonging to the A. oxyrhyncha clade. It is plausible that some nominate taxa currently recognized as synonyms might show a similar pattern. For now, we recognize other members of the clade (CESS 211, CESS 506) as Ahaetulla cf. oxyrhyncha and members other than A. anomala as Ahaetulla sp., which require further scrutiny.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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Ahaetulla oxyrhyncha ( Bell, 1825 )
| Mallik, Ashok Kumar, Srikanthan, Achyuthan N., Pal, Saunak P., D’Souza, Princia Margaret, Shanker, Kartik & Ganesh, Sumaithangi Rajagopalan 2020 |
Dryophis passericki
| Schinz 1833 |
Dryinus rostratus
| Schinz 1833 |
Dryinus oxyrhynchus
| Bell 1825 |
Dryinus russellianus
| Bell 1825 |