A revision of the Oligodon taeniatus (Günther, 1861) group (Squamata: Colubridae) , with the description of three new species from the Indochinese Region

Abstract

The group of Asian colubrid species morphologically similar to Oligodon taeniatus (Günther, 1861), previously containing only O. taeniatus, Oligodon mouhoti (Günther, 1864) and Oligodon barroni (Smith, 1916), is revised on the basis of variation in external morphology and dentition of 175 specimens. The confused nomenclatural history of O. taeniatus and its name bearing type is discussed. A neotype is described for Simotes quadrilineatus Jan & Sordelli, 1865, a synonym of O. taeniatus. The holotype of Simotes taeniatus var. mouhoti Boulenger, 1914 is identified. Three new species within this group are described. Oligodon pseudotaeniatus spec. nov. is described on the basis of specimens from central Thailand. This species is morphologically similar to Oligodon taeniatus, but differs by the combination of 17 dorsal scale rows at midbody, 8 supralabials, the absence of dark dorsal and tail blotches and the presence of a vertebral stripe edged with black but no dorsolateral stripes. Oligodon deuvei spec. nov. is described on the basis of specimens from southern Vietnam and Laos; it differs from other known species of the group by the combination of 12–15 maxillary teeth, 17 dorsal scale rows at midbody, usually seven supralabials, the absence of dark dorsal and tail blotches and the presence of a broad vertebral stripe, often conspicuously orange or rusty red. This species is most similar to Oligodon barroni but differs from the latter by a higher number of maxillary teeth and the absence of dark dorsal and tail blotches. Lastly, Oligodon moricei spec. nov. is described on the basis of a single specimen from southern Vietnam. It differs from other species by the combination of a broad rusty brown vertebral stripe edged with two broad black stripes, 12 maxillary teeth, 17 dorsal scale rows, a high number of ventral scales, seven supralabials and a dark cloudy or smoky venter. These new species are compared with other species known from the Indo-Chinese Region. The diagnoses of O. taeniatus, O. mouhoti and O. barroni are revised. A key to members of the group is given.

A new species of Oligodon Fitzinger, 1826 from the Langbian Plateau, southern Vietnam, with additional information on Oligodon annamensis Leviton, 1953 (Squamata: Colubridae)

“…The genus Oligodon is traditionally classified in informal species groups on the basis of the hemipenial morphology, number of dorsal scale rows and other characters (Smith, 1943;David, Das & Vogel, 2008;David et al, 2012;Vassilieva et al, 2013;Vassilieva, 2015). The role of hemipenial morphology in delimiting clades within Oligodon was also partially confirmed based on phylogenetic analysis by Green, Orlov & Murphy (2010).…”

“…The uncorrected p-distances for the 16S rRNA gene fragment among and within examined Oligodon species are presented in Table 3. Intraspecific distances varied significantly and ranged from p = 0% in a number of examined species to p = 2.3% in the O. cinereus complex and p = 2.8% in the O. cyclurus complex, what is most likely explained by incomplete taxonomy of these groups (Green, Orlov & Murphy, 2010;David, Das & Vogel, 2008;David et al, 2012); a more detailed study including topotype materials on these species complexes is required.…”

“…Comparisons. Morphological diagnostics of species based exclusively on hemipenial morphology is often complicated due to insufficiency of data and certain controversy in describing hemipenis character states in Oligodon existing in literature (Smith, 1943;Wagner, 1975;Vassilieva, 2015); scalation and coloration features often might be more useful for species identification (Pauwels et al, 2002;David, Das & Vogel, 2008;David et al, 2012;Neang, Grismer & Daltry, 2012;Nguyen et al, 2016;Nguyen et al, 2017) David,Vogel & Pauwels (17 or 18); O. culaochamensis Nguyen,Nguyen,Nguyen,Phan,Jiang & Murphy (17); O. condaoensis Nguyen,Nguyen,Le & Murphy (17); O. macrurus (Angel) (17); O. arenarius Vassilieva (17) and O. cattienensis Vassilieva,Geissler,Galoyan,Poyarkov,Van Devender & Böhme (17); phylogenetic position of the latter two species is unclear.…”

“…Due to their secretive behavior (Tillack & Günther, 2009), many species are known from only a few specimens or even only the holotype. Consequently, knowledge regarding Oligodon taxonomy, distribution, morphological variation and natural history is limited (Leviton, 1953;Leviton, 1960;Pauwels et al, 2002;David, Das & Vogel, 2008;Neang, Grismer & Daltry, 2012). In Vietnam 23 species of Oligodon have been recorded up to date, with six of them being country endemic, while eight species were described within the last decade (David, Das & Vogel, 2008;David et al, 2012;Nguyen et al, 2016;Nguyen et al, 2017;Vassilieva et al, 2013;Vassilieva, 2015).…”

“…Color characters and patterns were recorded during examination of specimens in life and taken from digital images of the living specimens. Morphological characters and morphometric ratios considered to be of taxonomic importance for Oligodon were used for species descriptions and followed a number of recent revisions of the genus (David, Das & Vogel, 2008;David et al, 2012;Leviton, 1953;Leviton, 1960;Neang & Hun, 2013;Nguyen et al, 2016;Nguyen et al, 2017;Vassilieva et al, 2013;Vassilieva, 2015). All body measurements, except body and tail lengths, were taken under a binocular microscope using digital slide-caliper to the nearest 0.1 mm.…”