Common names: Mexican lance-headed rattlesnake, lance-headed rattlesnake.

Crotalus polystictus is a venomous

Venomous snake

"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom...

 pitviper

Crotalinae

The Crotalinae, commonly known as "pit vipers" or crotaline snakes, are a subfamily of venomous vipers found in Asia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on either side of the head...

 species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

 found in central Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

. No subspecies are currently recognized.

Description

Adults usually grow to 60-70 cm, although exceptionally large specimens may be as much as 100 cm in length.

Geographic range

Found on the plateau of central Mexico

Mexico

The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...

 from southern Zacatecas

Zacatecas

Zacatecas officially Estado Libre y Soberano de Zacatecas is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 58 municipalities and its capital city is Zacatecas....

 and northeastern Colima

Colima

Colima is one of the 31 states which, with the Federal District, make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima....

 east to east-central Veracruz

Veracruz

Veracruz, formally Veracruz de Ignacio de la Llave officially Estado Libre y Soberano de Veracruz de Ignacio de la Llave , is one of the 31 states that, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided in 212 municipalities and its capital city is...

. Occurs at elevations between 1,450 m and 2,600 m. The type locality given is "Table Land, Mexico", although a restriction to "Tupátaro, Guanajuanto, Mexico" was proposed by Smith and Taylor (1950).

Conservation status

This species is classified as Least Concern (LC) on the IUCN

World Conservation Union

The International Union for Conservation of Nature and Natural Resources is an international organization dedicated to finding "pragmatic solutions to our most pressing environment and development challenges." The organization publishes the IUCN Red List, compiling information from a network of...

 Red List of Threatened Species

IUCN Red List

The IUCN Red List of Threatened Species , founded in 1963, is the world's most comprehensive inventory of the global conservation status of biological species. The International Union for Conservation of Nature is the world's main authority on the conservation status of species...

(v3.1, 2001). Species are listed as such due to their wide distribution, presumed large population, or because it is unlikely to be declining fast enough to qualify for listing in a more threatened category. The population trend is down. Year assessed: 2007.

External links

• Mexican Lance-headed Rattlesnake at the Saint Louis Zoo. Accessed 18 June 2008.