- Common name: Tancitaran dusky rattlesnake
Adult males may grow to more than 50 cm (20 in) in length. Females are smaller. The largest recorded length for a specimen is 68.2 cm (26.9 in).
Campbell and Lamar (2004) found this species only to be active during the day. Within its range, night temperatures are low and apparently restrict its activity.
It is found in west-central Mexico in the Sierra de Coalcomán of southwestern Michoacán, the Transverse Volcanic Cordillera of west-central Michoacán, and in adjacent Jalisco. It is probably also found in northeastern Colima. The type locality given is "Tancítaro, Michoacán, Mexico, altitude 5,000 ft" (5,000 ft = 1,524 m). It occurs at elevations between 1,525 and 2,380 metres (5,003 and 7,808 ft).
This species is classified as Endangered on the IUCN Red List of Threatened Species with the following criteria: B1ab(iii) (v3.1, 2001). A species is listed as such when the best available evidence indicates its extent of occurrence is estimated to be less than 5000 km2, estimates indicate its range is severely fragmented or known to exist at no more than five locations, and a continuing decline has been observed, inferred, or projected in the area, extent, and/or quality of its habitat. Therefore, it is considered to be facing a very high risk of extinction in the wild. The population trend was unknown when assessed in 2007.
- List of crotaline species and subspecies
- Crotalus by common name
- Crotalus by taxonomic synonyms
- Crotalinae by common name
- Crotalinae by taxonomic synonyms
- McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).
- Campbell JA, Lamar WW. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing Associates, Ithaca and London. 870 pp. 1500 plates. ISBN 0-8014-4141-2.
- "Crotalus pusillus". Integrated Taxonomic Information System. Retrieved 1 August 2007.
- Crotalus pusillus at the IUCN Red List. Accessed 13 September 2007.
- 2001 Categories & Criteria (version 3.1) at the IUCN Red List. Accessed 13 September 2007.
- Klauber, L.M. 1952. Taxonomic studies on rattlesnakes of Mainland Mexico. Bull. Zool. Soc. San Diego 26:1-143.