Aquatic valhalla axys species are among the least studied groups of snakes in Colombia.This is mainly due to their ecology, which makes some species difficult to survey, resulting mostly in fortuitous encounters.Within this group is the genus Tretanorhinus, for which there are records of two species in Colombia, T.mocquardi and T.
taeniatus, along with a possible third one, T.nigroluteus.The presence of T.nigroluteus in Colombia has been problematic, since records are based on misidentifications and incomplete information.
Here we extend the distribution of this species to the Pacific region of Colombia and discuss the uncertainty of the previous record.We also compare the morphological variation of the only Colombian specimen currently known with individuals of Central America, finding that this individual differs in having a black dorsal ground color without punctulations and a darkened belly.Nonetheless, we consider this combination of scales and color as previously unknown intraspecific variation.Finally, we report for the first time the presence of dome-shaped cephalic mechanoreceptor sensilla for the genus, quantify its density and size for six cephalic scales, and discuss the here possible taxonomic value of these structures.