Boiga nuchalis ( Günther, 1875 )

Ganesh, S. R., Achyuthan, N. S., Chandramouli, S. R. & Vogel, Gernot, 2020, Taxonomic revision of the Boiga ceylonensis group (Serpentes: Colubridae): reexamination of type specimens, redefinition of nominate taxa and an updated key, Zootaxa 4779 (3), pp. 301-332 : 311-314

Boiga nuchalis ( Günther, 1875)

( Tables 3–4; Fig. 6 , Fig. 9D )

Dipsas nuchalis Günther, 1875

Dipsas ceylonensis (non Dipsadomorphus ceylonensis Günther, 1858 )— Boulenger (1890) part

Boiga ceylonensis (non Dipsadomorphus ceylonensis Günther, 1858 )— Smith (1943) part; Hutton (1949) part; Hutton & David (2009) part

Boiga nuchalis (non Dipsadomorphus nuchalis –Wall, 1911)— Günther (1875); Inger et al. 1984

Boiga ceylonensis dakhunensis Deraniyagala, 1955

Specimens examined. Males (n=10).

Syntypes. Males : India . BMNH 74.4 .29.935, BMNH 74.4 .29.933, 36; Females: BMNH 74.4 .29.934, 37 and BMNH 74.4 .29.967, all collected by R.H. Beddome from the “ West Coast Forests ”[of India] . Additional Specimens: India. Tamil Nadu. MNHN 1946.69 and MNHN 1948.301 both Yercaud, Salem ; BNHS 1891 Benhope, Nilgiris. Kerala . FMNH 217700 Trivandrum ; BNHS 1842 Palagapandy, Palghat ; BNHS 1890 Travancore ; BNHS 1887 Kartikolam, Mananthavadi, Waynad District .

Females (n=8). India. Tamil Nadu. CAS 17248 Anama Kays [Anaimalais] Madras [Presidency]. BNHS 1893 Anamallai hills, 3000 ft. Kerala. BMNH 1924.10.13.19 Kattayam [Kottayam], Travancore; BNHS 1843 Nilambur; BNHS 1845 Nelliampathy, Palghat.

Taxonomic history. Boiga nuchalis was described by Günther (1875), as Dipsas nuchalis , from the “the forests of the West Coast [of India]”. It was later synonymised with Boiga ceylonensis by Boulenger (1890). Wall (1909) recognized it again as a valid species after having revised the Boiga ceylonensis -group and described two more species, B. beddomei and B. andamanensis . Smith (1943) once again synonymised B. nuchalis with B. ceylonensis . Inger et al. (1984) considered B. nuchalis as a valid species and this view was followed by most of the recent authors ( Das 2002; Ganesh & Arumugam 2016; Ganesh et al. 2018).

Nomenclatural notes. Deraniyagala (1955) misunderstood the fact that Wall (1909; 1911) had wrongly attributed the authorship of the taxon Dipsas nuchalis Günther to Beddome. It should be noted that this authorship credited to Beddome is purely a lapsus as we could not trace any mention of Dipsas nuchalis by this latter author. Nevertheless, believing B. nuchalis Beddome sensu Wall was a distinct, valid taxon on its own, Deraniyagala created an unnecessary new taxon, with the status of a nomen novum, Boiga ceylonensis dakhunensis Deraniyagala, 1955 . But Wall’s cursorial mistake in attributing B. nuchalis to Beddome cannot be considered to be the description of an available taxon on its own and therefore it does not enter into homonymy. There cannot be any doubt that the authorship and date of the nomen Dipsas nuchalis is Günther, 1875 (also see Vogel & Ganesh 2013; Wallach et al. 2014; Aengals et al. 2018). Günther (1875) only mentioned Beddome as the collector of the types (see Günther 1875: 233). Deraniyagala stated, erroneously, that “Günther’s name nuchalis cannot be utilized for the latter [south Indian population], since it was employed by Beddome for another species (see Wall 1909: 153). The name dakhunensis is proposed for the Indian subspecies of B. ceylonensis .” He was expressly intending to create this as a nomen novum (or replacement name) for Indian populations (see Art. 13.1.3 ICZN 1999). Deraniyagala was obviously erroneous in this interpretation as, whatever may have been written by Wall (1909), Dipsas nuchalis Günther, 1875 would have had priority over any “ Boiga nuchalis Beddome ”. So Deraniyagala should have had considered this “ Dipsas nuchalis Beddome ” to be a primary homonym of Günther’s taxon, and thus permanently invalid. Deraniyagala (1955) embraced an obsolete concept of B. ceylonensis in Indian Peninsula that included supposedly synonymous taxa like B. beddomei , B. nuchalis and B. andamanensis . As he wrote, his replacement name at the subspecific level was correctly based on the types of Dipsias nuchalis (sic, for Dipsas nuchalis ). This is in accordance with Art. 72.7 of ICZN (1999). Because Deraniyagala mentioned characters diagnosing (Recommendation 13A, ICZN, 1999) the taxa of the Boiga ceylonensis group between Western Ghats and Sri Lanka, and because he included Dipsas nuchalis in the synonymy of his Boiga ceylonensis account, this is an available name. Deraniyagala was in error in mentioning a single type, as Günther’s original description was based on five syntypes ( Günther 1875; Wallach et al. 2014). Therefore, by virtue of Deraniyagala’s typification and of the definition of a nomen novum, Boiga ceylonensis dakhuensis Deraniyagala, 1955 is deemed to be an objective junior synonym of Dipsas nuchalis Günther, 1875 as per Art. 72.7 of ICZN (1999). Contrary to Deraniyagala’s misconception (also see Sharma 2004; Wallach et al. 2014) Deraniyagala’s nomen is not a subspecies of Dipsadomorphus ceylonensis Günther, 1858 .

Etymology. Named after its typical collar band on the nuchal region.

Diagnosis (redefined herein). A species of Boiga endemic to southwestern India, characterised by the following combination of characters: 21–23 midbody scale rows (vs. 19 in B. ceylonensis , B. thackerayi , B. beddomei , B. flaviviridis ); vertebral scales strongly enlarged (vs. mildly enlarged in B. barnesii ); venter brownish-grey and not yellowish in life (vs. yellowish-brown in B. thackerayi , B. flaviviridis ; variable in B. andamanensis ; dorsum predominantly brown (vs. green in B. flaviviridis ; variable in B. andamanensis ); bars brown or reddish-brown (vs. bars black in B. thackerayi , B. beddomei ); ventrolateral pattern with a series of spots on both tips of each ventral scale (vs. with alternate white and black blotches in B. barnesii , B. thackerayi ; without any pattern in B. andamanensis , B. flaviviridis ); temporal larger than coastal body scale (vs. subequal to coastal body scale in B. dightoni ).

Redescription of an adult male syntype (BMNH 74.4.29.935). A medium-sized specimen reaching 900 mm total length, with slender habitus, thin neck, wide head; long tail (relative tail length 22 %); dorsal scale rows 21:21:15; rostral visible from above; preocular 1, subequal in size to loreal; postoculars 2; loreal 1; supralabials 8, with 3 rd– 5 th / 4 th– 6 th ones touching eye; infralabials 11, with 1–5 touching chin shields; temporals 13/14; preventral 1; ventrals 242, angulate laterally; cloacal 1; 105 subcaudals pairs. Dorsal colour brownish-grey, with 66 brownish crossbars on body; crossbars covering 2–4 scales in size, extending either sides up to 3–4 scale rows across; interspaces often with sparse dark dots; crown without any markings on top (rarely some dark shades present); a distinct postocular stripe up to the jaw angle; labials, chin and venter ashy brown, finely spotted with darker shade; venter bordered by a series of brown spots, covering both the terminal ends of every ventral scale.

Variation shown by other syntypes and referred material. Other specimens agreeing with the above syn- type in most aspects; showing the following intraspecific variations: snout to vent length 408–904 mm (excluding juveniles); tail length 94–257 mm; relative tail length: 18.7–22.5 %; (18)21/23–21/23–15(14) scale rows; temporals 10–15; ventrals 228–255; subcaudals 94–109 pairs; number of cross bars 45–89 on body, 7–36 on tail.

Distribution and natural history. This is perhaps the most common species of the genus Boiga in the wet forests of southwestern India. Often regarded as a rare and little-known species ( Das 2002), it occurs at quite a widespread and sometimes disjunct range in southwestern India. This species has been recorded throughout the Western Ghats ( Wall 1919; Inger et al. 1984; Hutton & David 2009 part; Chandramouli & Ganesh 2010; Ganesh et al. 2013) and even in Southern Eastern Ghats ( Ganesh & Arumugam 2016; Ganesh et al. 2018). It has been precisely reported from Agasthyamalai ( Inger et al. 1984; Chandramouli & Ganesh 2010), Meghamalai and Anaiamalai ( Hutton & David 2009 part), Nilgiri-Wayanad ( Wall 1919), Malnad and Canara hills (Ganesh et al. 2013) in the Western Ghats. In the Eastern Ghats, this species has been recorded from Shevaroys, Bilgiri, Melagiri, Kolli and Sirumalai hills ( Ganesh & Arumugam 2016; Ganesh et al. 2018). We have observed it in Ponmudi, Karian Shola and Agumbe in Western Ghats and in Bilgiri, Melagiri, Shevaroys, Kolli and Sirumalai in the Eastern Ghats (Fig. 13). However, we refute its purported (historical) distribution in Himalayan foothills and parts of Northern Eastern Ghats ( Wallach et al. 2014). We suggest that this species is absent from North India (also see Mohapatra et al. 2010; Das et al. 2010).

Figures

FIGURE 6. A syntype of Boiga nuchalis BMNH 74.4.29.935 from West Coast Forests. (A) entire—dorsal, (B) entire—ventral, (C) ventral pattern close-up, (D) head—ventral, (E) head—lateral, (F) head—dorsal views. (southern India)

FIGURE 9. (A&B) Boiga ceylonensis from Kanneliya & Hunasgiriya, Sri Lanka; (C) Boiga beddomei from Pune, India; (D) Boiga nuchalis from Anaimalai, India; (E) Boiga barnesii from Kandy, Sri Lanka; (F) Boiga andamanensis from Andaman Islands, India.