Melanophidium Günther, 1864

Pyron, Robert Alexander, Ganesh, Sumaithangi Rajagopalan, Sayyed, Amit, Sharma, Vivek, Wallach, Van & Somaweera, Ruchira, 2016, A catalogue and systematic overview of the shield-tailed snakes (Serpentes: Uropeltidae), Zoosystema 38 (4), pp. 453-506 : 473

Melanophidium Günther, 1864

Melanophidium Günther, 1864: 193 .

TYPE SPECIES. — Plectrurus wynaudensis Beddome, 1863a by original monotypy.

INCLUDED SPECIES. — Melanophidium bilineatum Beddome, 1870 , M. khairei , M. punctatum , M. wynaudense .

DIAGNOSIS. — Melanophidium can be distinguished from all other amniotes by the characters given for the family, and from other uropeltids by a mental groove, dorsal scales in 15 rows at midbody, eye in ocular shield, and no temporal. At least three species ( M. bilineatum , M. punctatum , and M. wynaudense ) have a unique micro-ornamentation pattern of dorsal scales at midbody, having large (> 18.5 mm), rounded polygonal Oberhäutchen cells with level borders and no denticulations ( Gower 2003). These characters separate them from 16 other uropeltid species from all genera except Pseudoplectrurus , and are thus likely also diagnostic characters. In recent studies of skull morphology, the following characters are shared by M. punctatum and M. wynaudense , but not by any sampled representatives of other uropeltid genera (i.e. they are likely, but not definitely, diagnostic of Melanophidium ; though Pseudoplectrurus and Teretrurus were not sampled): supraoccipital separate, prootic and opisthotic-exoccipital separate, basisphenoid-basioccipital separate, facial nerve branches into open recess behind the mandibular branch foramen which connects with the posterior opening of the Vidian canal, and posteroventral process of dentary distinct ( Rieppel & Zaher 2002; Olori & Bell 2012).

DISTRIBUTION. — India, in the Western Ghats as far North as Amboli ( Whitaker & Captain 2004; Gower et al. 2016).

DESCRIPTION

Tail is longer (up to 8% SVL; see Rajendran 1985; Table 2) than in most other uropeltids, but not as heavily compressed or modified; caudal scales are unkeeled and terminal scute is small and smooth or terminates in two to four points. In the single specimen of M. wynaudense dissected, no aspect of visceral topology is significant in uniquely distinguishing it from other uropeltid genera. However, mean of the heart-liver interval (15% of SVL) is larger than that measured for any other uropeltid genus, the next largest being Rhinophis (10% SVL; Table 3). All four species with teeth on the palatine, a condition otherwise absent in Uropeltidae ( Rieppel & Zaher 2002; Cundall & Irish 2008; Olori & Bell 2012; Gower et al. 2016). However, this condition is variable in M. wynaudense , with most examined specimens lacking teeth (Gower et al. 2016). All species exhibit a striking blue-green iridescence, which is still noticeable in preservative as it derives from microstructural features in the scales, rather than pigments (see Gower 2003). Few objective and unambiguous external morphological features separate the known species, which are identifiable primarily based on color pattern ( Smith 1943; Gower et al. 2016). Monophyly of this genus has been questioned in the past ( Rieppel & Zaher 2002), but is supported by our molecular phylogeny (part), the presence of a mental groove, and the unique features of scale micro-ornamentation and skull morphology (part) given in the diagnosis ( Rieppel & Zaher 2002; Gower 2003; Olori & Bell 2012; Gower et al. 2016).

REMARKS

A lack of comparative analyses hid the existence of Melanophidium khairei for 144 years, disguised as M. punctatum (see Gower et al. 2016). Extralimital records and confounding character-states exist for each species (see below and Gower et al. 2016); there is likely additional cryptic and undiscovered diversity in this group, as with most uropeltid genera.