Hydrophis stokesii ( Gray, 1846 )

Ganesh, S. R., 2025, On a forgotten record of Stoke’s sea snake Hydrophis stokesii (Gray, 1846) from the Kerala Coast, southwestern India (Squamata: Elapidae), Zootaxa 5637 (2), pp. 394-398 : 395-396

Hydrophis stokesii ( Gray, 1846)

( Fig. 1a–d )

Description of TNHM(H)-133 labelled “ Distira stokesii, Trev. 4 Nov: 94 purchased”.- stout body build, thick stocky trunk, large head, broad tail; eyes and nostrils beset on snout top; rostral much broader than long, supralabials 10/11 (3 rd, 4 th entering orbit); infralabials 11/10; mental small, fairly narrow; chin shields barely larger than adjacent infralabials; median groove small, barely discernable; nasals large, next only to parietals in size, broadly contacting one another; nasals pierced by nostril, situated at posterior end of nasals, near prefrontal border; prefrontal pair, smaller, half the size of frontal, much broader than long; frontal hexagonal, subequal to supraoculars; supraocular produced anteriorly; preocular 1/1; postoculars 2/2; parietals large, lung-shaped, with a small dent at midline suture; anterior temporal 1/1; posterior temporals 2/2; dorsal scale rows 41: 51: 45; ventrals 250, single and narrow anteriorly, paired posteriorly by a cleft-like median furrow, forming foliform scales; snout-vent length 1000mm; tail length 150mm; head length 80mm; head width 40mm; eye-diameter 10mm; inter-orbital distance 23mm; inter-narial distance 11mm; eye-nostril distance 10mm; eyelip distance 8mm; midbody height 100mm; midbody width 45mm; dorsal body overall creamy off-white with dark grey cross bands; labials, venter and gular regions creamy off-white; 20 dark grey cross bands on body, 5 on tail; each dark grey band ranging from 4–10 scales wide in places, narrowest on neck, widest on midbody; lighter anteriorly, lightest on collar mark, darkening in tone posteriorly.

This historical, 130 years old display gallery specimen was briefly examined with due caution and diligence owing to its academic importance and potential fragility. The features reported here, agree with the definition of H. stokesii ( Boulenger 1890, 1896; Wall 1909; Smith 1926, 1943; Whitaker & Captain 2004; Rasmussen et al. 2011, 2014; Sasai et al. 2021) and thereby ratifies the identity as reported by Ferguson (1895). It is known that the Scottish zoologist Harold Stuart Ferguson (1851–1921) was a key officer with the Thiruvananthapuram Natural History Museum. It is also known that the remaining sea snake specimens stored there at the museum, are all from the Thiruvananthapuram Coast and are sourced through fishermen, by Ferguson, who deposited them with the museum holdings ( Ferguson 1895, 1902). At least one other specimen of another estuarine / marine snake species, i.e., Dieurostus dussumierii was also recovered during my joint study, which was consequently depicted and described recently ( De Souza et al. 2024). Unlike the H. stokesii however, D. dussumierii specimen was collected in 1914, many years after his studies on snakes ( Ferguson 1895, 1902). It is surprising to note that despite the precise record of H. stokesii from Trevandrum or Travancore Coast by Ferguson (1895), even recent treatises on the subject did not include South Kerala Coast in its distribution range and that some compilations on the reptiles of Kerala did not include this species ( Palot 2015, 2021).

To the best of my knowledge, this is the first description of a well-identified Indian specimen of H. stokesii . The only other precise records of H. stokesii from India are from Sandheads, Bengal, by virtue of the type localities of the synonyms whose types are now lost ( Smith 1926; Das et al. 1998; Mondal et al. 2022). Whitaker & Captain (2004) featured H. stokesii with one from Visayan Sea, Philippines, depicted, adding that its range is “Bay of Bengal; also Singapore and Australia ”, while marking the range in the Indian map only in the Sundarbans. The Kerala Coast record, off the Arabian Sea, got unfortunately excluded both in the text and map of H. stokesii by them. In iNaturalist, a post depicting an identified and captioned photograph showing a dead H. stokesii washed off on beach observed by the user “jessicaluis” on Apr 21, 2018, 5:30 PM IST from an unnamed Road (19.37057N, 72.76193E), Bhuigaon, Nalasopara West, Nala Sopara, Maharashtra 401201, India (https://www.inaturalist.org/ observations/12380523). This is another record from the Arabian Sea, albeit northwards in the Konkan Coast. A recent study in the nearby Sri Lankan Coast also did not yield any sightings of H. stokesii (see Ukuwela et al. 2022). According to Deraniyagala (1955 in, de Silva 1994), the species was recorded from “Vaduga Banks, Pesali, Colombo, Panadura and Galle”; while Haly (1886) found it at Pearl Banks, in Sri Lanka. A review by Somaweera & Somaweera (2009) summarised the Sri Lanka records of H. stokesii as from Colombo, Galle, Panadura, Peysalai, Pt. Pedro and Puttalam.

Sasai et al. (2021) first reported H. stokesii from Okinawa waters, revealing that its distribution is still incompletely known. Against this backdrop of unsettled and contentious texts and obscure reports, this work gains prominence by depicting and describing the specimen involved and ratifying the Kerala Coast record of H. stokesii by Feguson (1895) to a good extent. Further surveys in India’s west (Konkan, Travancore) and east coasts (Sundarbans) are thus needed, to assess the occurrence of the elusive H. stokesii from its previously known but overlooked localities.

Figures

FIGURE 1. Hydrophis stokesii, specimen TNHM(H)-133 showing (a) jar label; (b) habitus, dorsal view; (c) habitus, ventral view; (d) head, lateral view; (e) reproduction of the original description plate of Hydrophis stokesii by Gray (1846), showing habitus and head profile drawings.