Report of Nagarjunasagar Racer Coluber bholanathi Sharma, 1976 (Squamata: Serpentes: Colubridae) from the Gingee Hills, Tamil Nadu, India
Utpal Smart 1, Eric N. Smith 2, B.H.C.K. Murthy 3 & Arun Mohanty 4
1,2 Amphibian and Reptile Diversity Research Center, Department of Biology, University of Texas at Arlington, Texas 76019-0498, USA
3 Zoological Survey of India, Prani Vigyan Bhawan, M-Block, New Alipore, Kolkata, West Bengal 700053, India
4 Sri Aurobindo Ashram, Pondicherry 605002, India
1 firstname.lastname@example.org (corresponding author), 2 email@example.com, 3 firstname.lastname@example.org, 4 email@example.com
The Nagarjunasagar Racer (or SharmaÕs Racer) Coluber bholanathi Sharma, 1976 was described based on three specimens (one male holotype ZSI 21337 and two female paratypes ZSI 21335, ZSI 21336) which were collected from Nagarjuna Hills (16”31ÕN; 79”14ÕE; 105m) in Guntur District, Andhra Pradesh State, India (Sharma 1976, 2003; Gupta et al. 2012; Ganesh et al. 2013; Seetharamaraju & Srinivasulu 2013). Sharma (1976, 2003) states that this species is diurnal and found in rocky habitats covered in a mix of evergreen and deciduous xerophytic vegetation. Judging from his dissection of the female specimen, Sharma (1976) remarked that this species preys upon gecko (Hemidactylus brookii). The climate of the type locality is described as hot and dry from March to October, with rainfall during the south-west, and north-east monsoons between November and February (Sharma 1976).
After several decades of obscurity, this species was recently reported from the Seshachalam Hills in southern Andhra Pradesh (Gupta et al. 2012), Golconda Fort Complex in Hyderabad City, Devarakonda in Nalgonda District, both situated in central Andhra Pradesh (Ganesh et al. 2013; Seetharamaraju & Srinivasulu 2013) and Thally in Krishnagiri District, northern Tamil Nadu (Ganesh et al. 2013). In addition to reporting new localities for Coluber bholanathi, Gupta et al. (2012) provided the first in-life illustration of this species, Seetharamaraju & Srinivasulu (2013) elaborated on the hemipineal morphology of the species as described by Sharma (2003) and Ganesh et al. (2013) provided the first illustration of the holotype while clearing up some confusion about its type registration number. Cumulatively, these three works have shed some light on this poorly-understood species.
In this note we provide the first report of Coluber bholanathi from the Gingee Hills, Villupuram District, northeastern Tamil Nadu. The snake which was ~40cm long (Image 2), was photographed by A. Mohanty on the morning of 6 December 2004 on a rocky hillock (12”06Õ16ÕÕN, 79”22Õ46ÕÕE; 115m) overlooking the Panamalai Lake (Image 1; Table 1). This lake is one of the many reservoirs that are scattered along the scenic Gingee Hills that run parallel to the east coast of Tamil Nadu. The Gingee Hills, which are a discontinuous southern extension of the Eastern Ghats, are a mixture of dry deciduous scrub forest and thorn scrub (Ramamurthy 1962; Champion & Seth 1968).
The snake was observed and photographed at a distance of ~50m away before it escaped into a series of boulders. We used the photograph provided in this note (Image 2) and three more, which provided several different angles of the animal, to identify the snake as Coluber cf. bholanathi based on color pattern and dorsal scale rows at one head-length behind the head, at midbody, and at one head-length anterior to the vent. Due to C. bholanathiÕs close resemblance to C. gracilis, we also examined the type specimens of C. bholanathi. Coluber gracilis (Gnther 1862) is another Indian species of Coluber, reported only from a few localities in the Satpura mountain ranges and northern Western Ghats from the states of Gujarat, Maharashtra, Madhya Pradesh and Rajasthan (Mahendra 1948; Ingle 2002; Sharma 2003; Whitaker & Captain 2004; Vyas et al. 2011; Walmiki et al. 2012; Table 1). ItÕs found in similar habitat type as C. bholanathi, e.g., rocky habitats with sparse, low, and thorny vegetation, although it is also reported to inhabit plains and open fields (Ingle 2002).
After close examination of the photographs, digital sharpening, and identifying the approximate midline of the animal, we found that the dorsal scales of the observed specimen from Gingee Hills were in (no more than) 19:19:17 rows. This count is closer to that observed in C. bholanathi (19:19:15 rows) than it is to C. gracilis (21:21:15 rows) (Sharma 1976). We observed additional differences in the patterning of the nuchal, oval blotch; in C. gracilis, the blotch appears to usually have an inverse V at its posterior margin (Image 3), whereas in C. bholanathi, the posterior margin tends to be either round or it fuses with the subsequent blotch forming a single large and elongate blotch (Image 5). The Gingee specimen has a nuchal blotch that has a round posterior margin, as observed in several specimens, including the type of C. bholanathi (Image 2). Moreover, C. bholanathi and the Gingee Hills specimen both possess a dark brown parietal bar that is interrupted laterally by light coloration at the post-temporal area adjacent to the parietal scales. In C. gracilis, however, the dark parietal bar widens towards the last two supralabials, typically forming an inverted ŅYÓ (Image 4).
Based on similarities in diagnostic morphological characters (namely: dorsal scale counts, nuchal marking and color pattern) and the geographic proximity of verified records (Gupta et al. 2012; Ganesh et al. 2013), we identified the Coluber from Gingee Hills as C. bholanathi. Our new record extends the known range of the species by 495km south of the type locality and 194km south-east of the southernmost locality (Ganesh et al. 2013). Our note also provides encouraging prospects that the geographic range of this obscure and rare species is probably larger than documented and we propose that the Gingee hills and adjacent suitable habitat warrant a more thorough sampling.
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