<br> The Tam Dao Mountain Stream Keelback,<br> Opisthotropis tamdaoensis<br> Ziegler, David & Vu, 2008, was previously described, based on one single holotype and subsequently expanded according to four newly-collected specimens from the type locality. Information on this species is extremely limited.<br> <br> <br> On the basis of newly-collected<br> Opisthotropis<br> specimens from Hekou, Yunnan, China, this study reports the first country record of<br> Opisthotropis tamdaoensis<br> from China. The Chinese<br> Opisthotropis tamdaoensis<br> population totally agrees with the original description of this species and revealed only a minor genetic distance (lower than 2.9%) in the mitochondrial gene fragment of the cytochrome<br> b<br> (<br> Cytb<br> ) compared with the topotypic population. Based upon the our newly-collected specimens and published data, we revised the diagnosis of<br> Opisthotropis tamdaoensis<br> :<br> <br> <br> <br> <br> nasal not divided below nostril;<br> <br> <br> loreal usually 1, not in contact with internasals;<br> <br> <br> pre-oculars 1–2, postoculars 2 subocular, usually 1;<br> <br> <br> anterior temporals 1–2, posterior temporals 2–4;<br> <br> <br> supralabials usually 9, only the fifth or fifth to sixth supralabial (rarely none) in contact with the orbit;<br> <br> <br> infralabials usually 9–10;<br> <br> <br> first pair of chin shields longer than the second pair;<br> <br> <br> dorsal scales smooth anteriorly, keeled posteriorly, in (17–19)-17-17 rows;<br> <br> <br> tails relatively short, TaL/TL 0.143–0.161;<br> <br> <br> pre ventrals 0–4, ventrals 160–176, precloacal divided; 48–56 divided subcaudals;<br> <br> <br> uniform olive-grey dorsum, with a dark longitudinal lateral stripe within the dark flank colouration, ventral side pale or light yellow, without sharp transition towards the dark dorsal colouration, subcaudal region may bear dark mottling.<br> <br> <br> <br> nasal not divided below nostril;<br> loreal usually 1, not in contact with internasals;<br> pre-oculars 1–2, postoculars 2 subocular, usually 1;<br> anterior temporals 1–2, posterior temporals 2–4;<br> supralabials usually 9, only the fifth or fifth to sixth supralabial (rarely none) in contact with the orbit;<br> infralabials usually 9–10;<br> first pair of chin shields longer than the second pair;<br> dorsal scales smooth anteriorly, keeled posteriorly, in (17–19)-17-17 rows;<br> tails relatively short, TaL/TL 0.143–0.161;<br> pre ventrals 0–4, ventrals 160–176, precloacal divided; 48–56 divided subcaudals;<br> uniform olive-grey dorsum, with a dark longitudinal lateral stripe within the dark flank colouration, ventral side pale or light yellow, without sharp transition towards the dark dorsal colouration, subcaudal region may bear dark mottling.<br> <br> This finding broadly extends our understanding of this poorly-known snake species and raises the total known<br> Opisthotropis<br> number in China to 14. Moreover, this study reports the second<br> Opisthotropis<br> species in Yunnan Province, China.<br>
