However, variation is a continuum that is not always easy to quantify. At one extreme, multiple species can look alike even though they are different species—these are known as cryptic species. At the other extreme, a single species can be highly variable, creating an illusion of being different. But what happens when you encounter both extremes simultaneously?

Herpetologist Dr. Chan Kin Onn (previously at the Lee Kong Chian Natural History Museum, Singapore, now with the University of Kansas Biodiversity Institute and Natural History Museum, USA) led a study describing a new species of pit viper from Myanmar that is similar and different from its sister species.

The discovery is published in ZooKeys.

"Asian pit vipers of the genus Trimeresurus are notoriously difficult to tell apart because they run the gamut of morphological variation. Some groups contain multiple species that look alike, while others may look very different but are actually the same species," they say.

The redtail pit viper (Trimeresurus erythrurus) occurs along the northern coast of Myanmar and is invariably green with no markings on its body. A different species called the mangrove pit viper (Trimeresurus purpureomaculatus) occurs in southern Myanmar. This species typically has distinct dorsal blotches, and incredibly variable dorsal coloration including gray, yellow, brown, and black, but never green. Interestingly, in central Myanmar, sandwiched between the distribution of the redtail pit viper and the mangrove pit viper, a unique population exists that is green with varying degrees of blotchiness, which appears to be a blend between the redtail pit viper and the mangrove pit viper.