''Hypsiglena unaocularus'', commonly known as the Islas Revillagigedo night snake or Clarión night snake, is a

species In biology, a species is the basic unit of Taxonomy (biology), classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of ...

of small

colubrid Colubridae (, commonly known as colubrids , from la, coluber, 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest species of the family date back to the Oligocene epoch. Colubrid snakes are found on ever ...

snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found els ...

Clarion Island Isla Clarión, formerly called Santa Rosa, is the second largest, westernmost and most remote of Mexico's Revillagigedo Islands. The island is located west of Socorro Island and over from the Mexican mainland. It has an area of and three p ...

, initially described from a single specimen collected by

William Beebe Charles William Beebe ( ; July 29, 1877 – June 4, 1962) was an American naturalist, ornithologist, marine biologist, entomologist, explorer, and author. He is remembered for the numerous expeditions he conducted for the New York Zoologica ...

in 1936. During the next several decades, scientists were unable to detect any trace of the snake in their field studies. After an intensive search in 2013, a team of scientist identified 11 snakes that matched the original description of the species. They conducted a series of DNA tests to confirm that the Islas Revillagigedo nightsnake, formerly viewed as the subspecies '' Hypsiglena torquata unaocularis'', is genetically distinct from related mainland snakes and should be recognized as a full species.News Releases, Smithsonian Scientist Discovers Lost Species of Nightsnake in Mexico, The Smithsonian, May 19, 2014
/ref> While never formally declared extinct, this species remained absent from scientific literature due to two main factors: its home on Clarion is extremely remote and only accessible by military escort, significantly restricting the number of biologists who can access this area, and the snake's secretive, nocturnal behavior and dark coloration make it difficult to detect in the field. Because of the lack of follow-up sightings, scientists long presumed that Beebe had provided an incorrect locality for his specimen.

Description

The snakes are brownish black in color and have a characteristic series of darker spots on their head and neck and grows to be approximately 18 inches long.

Geographic range

The species is only found on the Mexican island of Clarion in the

Revillagigedo Islands The Revillagigedo Islands ( es, Islas Revillagigedo, ) or Revillagigedo Archipelago are a group of four volcanic islands in the Pacific Ocean, known for their unique ecosystem. They lie approximately from Socorro Island south and southwest of C ...

Habitat

It lives on black lava rock habitat near the waters of Sulphur Gay.

Origins

The Islas Revillagigedo nightsnake is believed to be most closely related to populations of snakes from in the Sonora-Sinaloa state border area of mainland Mexico and Isla Santa Catalina in the Gulf of California. The Clarion nightsnake likely originated from the dispersal of an ancestor that traveled by sea from a river basin in Sonora to Clarion.

Conservation status

While current populations of this species appear to be viable, Clarion's fragile ecosystem is threatened by invasive species such as feral cats on neighboring islands. These cats prey on lizards, which are likely a main food source for the Clarion nightsnake.

References

{{Taxonbar, from=Q16983484 Colubrids Endemic reptiles of Mexico Revillagigedo Islands Reptiles described in 1946 Taxa named by Wilmer W. Tanner