Lycodon cf. ruhstrati ( Fischer, 1886 )

Ziegler, Thomas, Hendrix, Ralf, Thanh, Vu Ngoc, Vogt, Martina, Forster, Bernhard & Kien, Dang Ngoc, 2007, The diversity of a snake community in a karst forest ecosystem in the central Truong Son, Vietnam, with an identification key, Zootaxa 1493, pp. 1-40 : 11-13

Lycodon cf. ruhstrati ( Fischer, 1886) : Ruhstrat's wolf snake / Ran khuyet rutrat

A female specimen (ZFMK 86451, SVL 466, TaL 142, TL 608 mm) was discovered at night of 20 June 2006, during the dry season, in the primary forest of U Bo region ( Figure 12 ). The specimen was crawling on the forest ground near a steep cascade at an altitude of about 520 m above sea level. Scalation features are as follows: Eight supralabials, of which third to fifth supralabials are in contact with eye; ten infralabials; one loreal, not in contact with eye; one preocular, not in contact with frontal; prefrontal not entering eye; two postoculars; two anterior temporals, followed by three posterior temporals; 17 dorsal scale rows at midbody, feebly keeled except for outermost rows; vertebral scales not enlarged; two undivided preventrals and 229 ventrals; ventrals distinctly angulate laterally; anal entire; 104 divided subcaudals. The specimen had 19 dark transversal crossbands on its body dorsum. These dark crossbands are largest anteriorly and become shorter towards the cloaca. The 18 interspaces of the dark body crossbands are creamy white in the neck region, but then become distinctly darker. After the first body third the light interspaces consist of a greyish-brown bar that is edged by white and contains in its centre a darker transversal bar. Such a pattern continues on the tail dorsum, which bears ten dark and 11–12 light crossbars, including the tail tip. The body venter is completely yellowish to cream in its anterior fourth, then in part interspersed with a brownish-grey marbling that becomes more intensive in the last body half. The dark dorsal crossbands continue on the underside of the tail.

The specimen clearly is a member of the genus Lycodon Boie , due to its pholidosis, a vertically elliptical pupil, and because of its arched maxillary bone, that is bent inwards anteriorly, with 6 anterior fang-like teeth increasing in size and separated by a toothless interspace of about 0.9 mm width at left side from 6 or 7 posterior teeth, the last two ones of which being enlarged ( Lanza 1999). In the key provided by Lanza (1999), the specimen from Phong Nha - Ke Bang, with some of its dorsal scale rows keeled along the whole body, clearly keys out as L. ruhstrati at point nine. From the similar L. fasciatus , which is a common snake around the limestone outcrops and caves in the karst forest of Phong Nha - Ke Bang, L. ruhstrati differs e. g. by the loreal not touching the eye, having slightly higher ventral (193–237 vs. 186–220) and subcaudal counts (77–119 vs. 66– 90), shorter posterior chinshields than the anterior ones (which is vice versa in the species fasciatus ), as well as in lacking dark bands that completely encircle the body, as it is the case in L. fasciatus ( Bourret 1936, Lanza 1999). Lanza (1999) further distinguishes in his key between the subspecies L. ruhstrati multifasciatus from Japan and the nominate form from southern China and Taiwan, with which our specimen appears to be conspecific at first glance.

However, Ota (1988) additionally found distinct meristic differences between the Taiwanese and continental populations of L. r. ruhstrati . These results might support the validity of Dinodon futsingensis Pope , that was described from "Futsing Hsien" in Fujian Province, continental China, and subsequently synonymized by Pope (1935) with L. ruhstrati (Fischer) , that was originally described as Ophites ruhstrati from southern Taiwan ( Fischer 1886). However, it is noteworthy, that Bourret (1936) states for " Dinodon futsingense ", that the dorsal scales are smooth and not keeled as it is the case in our recent finding from Phong Nha - Ke Bang. Pope's (1928) type specimen of Dinodon futsingensis had smooth scales and also another continental specimen that was studied by us (ZFMK 23363 from Fujian) as well as a specimen from the Vietnamese province Ha Tinh, listed as Lycodon ruhstrati in Ziegler (2002). However, Pope (1929) reported also on specimens from Fujian and Mell (1922) on a specimen from Guangdong, that bear dorsal keels. Taiwanese specimens known so far always had keeled dorsal scales ( Fischer 1886: type series O. ruhstrati, Maki 1931 , Vogel & Brachtel accepted).

Thus, future studies must clarify, whether the coexistence of continental representatives both with keeled and smooth dorsal scales is due to individual variation or rather indicating that different taxa are involved. It is further noteworthy, that female L. ruhstrati from continental China that were studied by Ota (1988) had lower ventral counts (197–227), lower subcaudal counts (77–95), and relatively higher transverse body and tail bands (22–38, 12–18) compared to our recent finding from Phong Nha - Ke Bang. Nguyen et al. (2005) list both Dinodon futsingensis and Lycodon ruhstrati as occurring in Vietnam: D. futsingensis from Lao Cai Province in the north southwards to Hoa Binh Province, and Lycodon ruhstrati from Cao Bang Province in the north to Da Nang Province in central Vietnam.

Figures

FIGURE 12. Portrait of the preserved specimen of Lycodon cf. ruhstrati from Phong Nha - Ke Bang (ZFMK 86451). Photo: Thomas Ziegler