A new species of the genus Oligodon Fitzinger, 1826 (Squamata: Colubridae) from coastal southern Vietnam

A new species of the genus Oligodon from the coastal area of Binh Chau-Phuoc Buu Nature Reserve, Ba Ria-Vung Tau Province, southern Vietnam, is described. Oligodon arenarius sp. nov. is distinguishable from all other species by the unique combination of the following characters: medium size; 17 dorsal scale rows; 6-8 maxillary teeth, the posterior three being enlarged; head scalation lacking a loreal but usually including a presubocular; divided nasal; two postoculars; 131-144 ventrals; 36-60 subcaudals; unforked hemipenis, without spines or obvious papillae; sexual dimorphism displayed in the number of subcaudals (36-40 in females, 58-60 in males) and a relative tail length, tails being quite long in males (TaL/TL = 0.26-0.28) and moderate in females (TaL/TL = 0.13-0.17); head coloration pattern including ocular band, temporal bands and chevron-shaped mark on nape; dorsal coloration without distinct pattern, uniform or with dark speckling; ventrals pinkish in life, immaculate. To date, this species appear to be endemic to Vietnam.