Notes on the hemipenis and head scalation of Oligodon arenarius Vassilieva, 2015 (Serpentes, Colubridae)

Traditionally, hemipenial morphology has been used as one of the key characters for identifying snakes. In kukri snakes, genus Oligodon, this organ is diverse in shape, length, papillae, spines, and flounces. Oligodon arenarius Vassilieva, 2015 was described from southern Vietnam as having short, unforked hemipenes without spines and papillae. Because of these hemipenial characters, the snake was not attributed to any species group of Oligodon. In addition, the snake has no loreal scales on its head. Based on an additional male collected from the type locality, we show that the hemipenes of O. arenarius in the original description were not fully everted. The fully everted hemipenes of this snake are deeply forked with two long and thin lobes, long, smooth, and without papillae. With this structure, the snake assigns to the O. cyclurus group. Further, a loreal scale is present on the left side of the head.