Common names: Mexican pigmy rattlesnake, Mexican pygmy rattlesnake, more.

Sistrurus ravus 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 only in 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...

. Three subspecies

Subspecies

Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...

 are currently recognized, including the nominate subspecies described here.

Description

Adults of this species usually grow to a length of 40-65 cm, but may reach more than 70 cm. They are moderately stout in build.

The distinguishing characteristics for S. r. ravus include parietal scales that are highly variable in shape, less than 3 prefoveals, 21 midbody dorsal scales

Dorsal scales

In snakes, the dorsal scales are the longitudinal series of plates that encircle the body, but do not include the ventral scales.When counting dorsal scales, numbers are often given for three points along the body, for example 19:21:17...

, 2-4 tail bands and a relatively large rattle.

Common names

Mexican pigmy rattlesnake, Mexican pygmy rattlesnake. Local names are víbora-cascabel pigmea-mexicana (Spanish

Spanish language

Spanish , also known as Castilian , is a Romance language in the Ibero-Romance group that evolved from several languages and dialects in central-northern Iberia around the 9th century and gradually spread with the expansion of the Kingdom of Castile into central and southern Iberia during the...

), colcóatl, cascabel enana, víbora de cascabel and viborita de cascabel.

Geographic range

Found only in 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...

 in the mountains in the center and south of the country, west of the Isthmus of Tehuantepec

Isthmus of Tehuantepec

The Isthmus of Tehuantepec is an isthmus in Mexico. It represents the shortest distance between the Gulf of Mexico and the Pacific Ocean, and prior to the opening of the Panama Canal was a major shipping route known simply as the Tehuantepec Route...

. Its range includes the southeastern part of the Mexican Plateau in the highlands of Mexico

Mexico (state)

México , officially: Estado Libre y Soberano de México is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of the United Mexican States. It is divided in 125 municipalities and its capital city is Toluca de Lerdo....

, Morelos

Morelos

Morelos officially Estado Libre y Soberano de Morelos is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 33 municipalities and its capital city is Cuernavaca....

, Tlaxcala

Tlaxcala

Tlaxcala officially Estado Libre y Soberano de Tlaxcala is one of the 31 states which along with the Federal District comprise the 32 federative entities of Mexico. It is divided into 60 municipalities and its capital city is Tlaxcala....

, Puebla

Puebla

Puebla officially Estado Libre y Soberano de Puebla is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 217 municipalities and its capital city is Puebla....

, 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...

, Oaxaca

Oaxaca

Oaxaca , , officially Estado Libre y Soberano de Oaxaca is one of the 31 states which, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided into 571 municipalities; of which 418 are governed by the system of customs and traditions...

 and the Sierra Madre del Sur

Sierra Madre del Sur

The Sierra Madre del Sur is a mountain range in southern Mexico, extending from southern Michoacán east through Guerrero, to the Istmo de Tehuantepec in eastern Oaxaca.-Geography:...

 in Guerrero

Guerrero

Guerrero officially Estado Libre y Soberano de Guerrero is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo....

. The type locality given is the "Table land of Mexico." Cochran (1961) interpreted this to be the "south tableland, Veracruz, Mexico."

Campbell and Lamar (2004) describe this species as being found across the Mexican Plateau in the temperate regions of moderate to high elevations. They estimate the vertical distribution to be from about 1,490 m above sea level to a little over 3,000 m altitude.

Subspecies

Subspecies	Taxon author	Common name	Geographic range
S. r. brunneus	Harris & Simmons, 1977	Oaxacan pigmy rattlesnake	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...  in the highlands of Oaxaca Oaxaca Oaxaca , , officially Estado Libre y Soberano de Oaxaca is one of the 31 states which, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided into 571 municipalities; of which 418 are governed by the system of customs and traditions... .
S. r. exiguus	Campbell & Armstrong, 1979	Guerreran pigmy rattlesnake	Mexico in the Sierra Madre del Sur Sierra Madre del Sur The Sierra Madre del Sur is a mountain range in southern Mexico, extending from southern Michoacán east through Guerrero, to the Istmo de Tehuantepec in eastern Oaxaca.-Geography:...  of central Guerrero Guerrero Guerrero officially Estado Libre y Soberano de Guerrero is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo.... .
S. r. ravus	(Cope Edward Drinker Cope Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen... , 1865)	Central Mexican pigmy rattlesnake	Mexico in the Altiplanicie Meridional, including the states of México Mexico (state) México , officially: Estado Libre y Soberano de México is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of the United Mexican States. It is divided in 125 municipalities and its capital city is Toluca de Lerdo.... , Morelos Morelos Morelos officially Estado Libre y Soberano de Morelos is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 33 municipalities and its capital city is Cuernavaca.... , Tlaxcala Tlaxcala Tlaxcala officially Estado Libre y Soberano de Tlaxcala is one of the 31 states which along with the Federal District comprise the 32 federative entities of Mexico. It is divided into 60 municipalities and its capital city is Tlaxcala.... , Puebla Puebla Puebla officially Estado Libre y Soberano de Puebla is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 217 municipalities and its capital city is Puebla....  and 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... .