The naturalist William Beebe embarked on a three-month expedition by sea in 1936 that took him from San Diego to Baja California to the Revillagigedo Archipelago off of Mexico, and during this journey, he collected bird, fish, invertebrate, and reptile samples that he sent to the American Museum of Natural History after he returned. One of those samples was a nightsnake from Isla Clarión.
In the 1940s, the Clarión nightsnake was determined to be a subspecies of Hypsiglena ochrorhyncha unaocularus, but further expeditions never encountered it again on the island, and that original sample was thought to be mislabeled.
Now, researchers from the US and Mexico say in PLOS One that they've re-discovered this snake and based on its mitochondrial DNA, they've determined that it is a distinct Hypsiglena species.
On this most recent expedition, the researchers collected DNA samples from nearly a dozen snakes — first spotted by a graduate student, NPR notes. After sequencing mitochondrial DNA from the snakes and comparing them to mtDNA from other snakes in the region and constructing a phylogenetic tree, they found that the Isla Clarión population was closely related to snake populations of the Sonora–Sinaloa state border area of mainland Mexico and Isla Santa Catalina.
But the Clarión nightsnakes, they add, are their own species, now dubbed Hypsiglena unaocualrus.