As most of us who work with reptiles and/or amphibians know, keeping up with the taxonomic status and scientific names of the various species is a continuing learning experience. The taxonomic standings of many of these animals are constantly evolving as we work to better understand them and continue to learn more about them utilizing the recent technologies available to us. To futher confuse matters, as these taxonomic changes occur, they do not always catch on with all herpetologists and herpetoculturists in a timely fashion with some herpetological workers being reluctant to accept the changes for various reasons.
Rattlesnakes belong to the taxonomic family Viperidae and to the subfamily Crotalinae commonly refered to as pitvipers, a name derived from the heat sensitive pit located on each side of the head between the eye and the nostril. There are 16 genera of Crotalinae snakes represented by about 150 species scattered throughout North America, South America, Europe and across Asia. Rattlesnakes make up 2 of these genera, Crotalus which occur throughout both North and South America, and Sistrurus which occur only in North America.
Rattlesnakes have undergone several taxonomic classification changes in recent years and it is anticipated that there will additional changes in the future.
As far back as 1973 studies concluded that what was then known as the Canebrake Rattlesnake, Crotalus horridus atricaudatus was not a valid subspecies of the Timber Rattlesnake, Crotalus horridus horridus. (Pisani, Collins, & Edwards. 1973. Transactions of the Kansas Academy of Science, 75:255-262). Their conclusion was not widely accepted and it was not until 30 years later in 2003 that their earlier work was corroborated using DNA. (Clark, Moler, Possardt, Savitzky, Brown, & Bowen. 2003. Journal of Herpetology 37 (1): 145-154). With the Canebrake Rattlesnake, Crotalus horridus atricaudatus being found to be nothing more than a geographic color variation of the Timber Rattlesnake, Crotalus horridus horridus, the subspecies atricaudatus was invalidated and today both forms are collectively known as the Timber Rattlesnake, Crotalus horridus. Even so, there are still a number of herpetoculturists who still insist on refering to the population from the southeastern United States as being the Canebrake Rattlesnake, Crotalus horridus atricaudatus.
Recent studies of the Western Rattlesnake Group which has consisted of nine different subspecies of Crotalus virdis found throughout the western United States, extreme southwestern Canada and extreme northern Mexico have led to a number of taxonomic changes within that group of rattlesnakes. In 2000 Pook, Wüster, & Thorpe conducted the first phylogeographic study of this Western Rattlesnake Group and suggested that three different full species should be recognized within the group. The following year Ashton & de Queiroz formally recognized two full species within the Western rattlesnake Group. Then in 2002 Douglas, Schuett, Porras & Holycross reviewed the systematics of the Western Rattlesnake Group using a mtDNA phylogeographic approach resulting in the recognition of seven full species and two subspecies within the group. The Western Rattlesnake Group is a very complex group of snakes and as such we should expect to see further research which may result in even more taxonomic changes being proposed for this group.
Another recent (2002) taxonomic change has been the reclassification of Sistrurus ravus and its associated subspecies from Sistrurus to Crotalus.
In 2004 Alvarado-Díaz Campbell (Herpetologica 60 (2): 281-286) described a new species of small montane rattlesnake from Cerro Tancítaro, Michoacán, México: Crotalus tancitarensis.
In 2004 Campbell & Lamar (Venomous Reptiles of the Western Hemisphere) split up the Crotalus durissus complex into three full species (durissus, simus, and totonacus). We can expect to see further taxonomic work being done with this complex in the future.
In 2007 Douglas, et al (Copia 4, 2007) elevated the Panamint Rattlesnake (Crotalus mitchellii stephensi) to species level.
In 2008 Campbell and Flores-Villela (Herpetologica 64 (2) 2008: 246-257) described a new species of Long-tailed Rattlesnake (Crotalus ericsmithi) from Guerrero, Mexico. AT this time this new species remains known only from the original type specimen.
Based upon the research currently available, the below listing represents what I believe to be the currently accepted forms of Crotalus and Sistrurus. This current listing contains a total of 84 forms or subspecies representing 38 species.
CROTALUS
Crotalus adamanteus, Eastern Diamondback Rattlesnake
Crotalus aquilus, Queretaran Blotched Rattlesnake
Crotalus atrox, Western Diamondback Rattlesnake
Crotalus basiliscus, Mexican West Coast Rattlesnake
Crotalus catalinensis, Santa Catalina Island Rattlesnake
Crotalus cerastes, Sidewinder
Crotalus cerastes cerastes, Mojave Desert Sidewinder
Crotalus cerastes cercobombus, Sonoran Desert Sidewinder
Crotalus cerastes laterorepens, Colorado Desert Sidewinder
Crotalus cerberus, Arizona Black Rattlesnake
Crotalus durissus, South American Rattlesnake
Crotalus durissus cascavella, Northeastern Brazilian Rattlesnake
Crotalus durissus collilineatus, Central Brazilian Rattlesnake
Crotalus durissus cumanensis, Venezuelan Rattlesnake
Crotalus durissus durissus, Guianian Rattlesnake
Crotalus durissus marajoensis, Marajoan Rattlesnake
Crotalus durissus ruruima, Mt. Roriama Rattlesnake
Crotalus durissus terrificus, South American Rattlesnake
Crotalus durissus trigonicus, Rupunini Rattlesnake
Crotalus enyo, Baja California Rattlesnake
Crotalus enyo cerralvensis, Cerralvo Island Rattlesnake
Crotalus enyo enyo, Baja California Rattlesnake
Crotalus enyo furvus, Rosario Rattlesnake
Crotalus ericsmithi, Guerreran Long-tailed Rattlesnake
Crotalus horridus, Timber Rattlesnake
Crotalus intermedius, Mexican Small-headed Rattlesnake
Crotalus intermedius gloydi, Oaxacan Small-headed Rattlesnake
Crotalus intermedius intermedius, Totalcan Small-headed Rattlesnake
Crotalus intermedius omiltemanus, Omilteman Small-headed Rattlesnake
Crotalus lannomi, Autlan Long-tailed Rattlesnake
Crotalus lepidus, Rock Rattlesnake
Crotalus lepidus castenaeus, Neuvo Leon Rock Rattlesnake
Crotalus lepidus klauberi, Banded Rock Rattlesnake
Crotalus lepidus lepidus, Mottled Rock Rattlesnake
Crotalus lepidus maculosus, Durango Rock Rattlesnake
Crotalus lepidus morulus, Tamaulipan Rock Rattlesnake
Crotalus mitchellii, Speckled Rattlesnake
Crotalus mitchellii angelensis, Angel de la Guarda Island Speckled Rattlesnake
Crotalus mitchellii mitchellii, San Lucan Speckled Rattlesnake
Crotalus mitchellii muertensis, El Muerto Island Rattlesnake
Crotalus mitchellii pyrrhus, Southwestern Speckled Rattlesnake
Crotalus molossus, Blacktail Rattlesnake
Crotalus molossus estebanensis, San Esteban Island Blacktail Rattlesnake
Crotalus molossus molossus, Northern Blacktail Rattlesnake
Crotalus molossus nigrescens, Mexican Blacktail Rattlesnake
Crotalus molossus oaxacus, Oaxacan Blacktail Rattlesnake
Crotalus oreganus, Western Rattlesnake
Crotalus oreganus abyssus, Grand Canyon Rattlesnake
Crotalus oreganus caliginis, Coronado Island Rattlesnake
Crotalus oreganus concolor, Midget Faded Rattlesnake
Crotalus oreganus helleri, Southern Pacific Rattlesnake
Crotalus oreganus lutosus, Great Basin Rattlesnake
Crotalus oreganus oreganus, Northern Pacific Rattlesnake
Crotalus polystictus, Mexican Lance-headed Rattlesnake
Crotalus pricei, Twin-spotted Rattlesnake
Crotalus pricei miquihuanus, Eastern Twin-spotted Rattlesnake
Crotalus pricei pricei, Western Twin-spotted Rattlesnake
Crotalus pusillus, Tancitaran Dusky Rattlesnake
Crotalus ravus, Mexican Pigmy Rattlesnake
Crotalus ravus brunneus, Oaxacan Pigmy Rattlesnake
Crotalus ravus exiguus, Guerreran Pigmy Rattlesnake
Crotalus ravus ravus, Central Plateau Pigmy Rattlesnake
Crotalus ruber, Red Diamond Rattlesnake
Crotalus ruber exsul, Cedros Island Diamond Rattlesnake
Crotalus ruber lorenzoensis, San Lorenzo Island Diamond Rattlesnake
Crotalus ruber lucansensis, San Lucan Island Diamond Rattlesnake
Crotalus ruber ruber, Red Diamond Rattlesnake
Crotalus scutulatus, Mohave Rattlesnake
Crotalus scutulatus salvini, Humantlan Rattlesnake
Crotalus scutulatus scutulatus, Mohave Rattlesnake
Crotalus simus, Neotropical Rattlesnake
Crotalus simus culminatus, Northwestern Neotropical Rattlesnake
Crotalus simus simus, Central American Neotropical Rattlesnake
Crotalus simus tzabcan, Yucatan Neotropical Rattlesnake
Crotalus stejnegeri, Sinaloan Long-tailed Rattlesnake
Crotalus stephensi, Panamint Rattlesnake
Crotalus tancitarensis, Tancitaran Rattlesnake
Crotalus tigris, Tiger Rattlesnake
Crotalus tortugensis, Tortuga Island Diamond Rattlesnake
Crotalus totonacus, Totonacan Rattlesnake
Crotalus transversus, Cross-banded Mountain Rattlesnake
Crotalus triseratus, Mexican Dusky Rattlesnake
Crotalus triseratus armstrongi, Mexican Dusky Rattlesnake
Crotalus triseratus triseratus, Central Plateau Dusky Rattlesnake
Crotalus unicolor, Aruba Island Rattlesnake
Crotalus vegrandis, Uracoan Rattlesnake
Crotalus viridis, Prairie Rattlesnake
Crotalus willardi, Ridgenose Rattlesnake
Crotalus willardi amabilis, Del Nido Ridgenose Rattlesnake
Crotalus willardi meridionalis, Southern Ridgenose Rattlesnake
Crotalus willardi obscurus, New Mexico Ridgenose Rattlesnake
Crotalus willardi silus, Western Chihuahuan Ridgenose Rattlesnake
Crotalus willardi willardi, Arizona Ridgenose Rattlesnake
SISTRURUS
Sistrurus catenatus, Massasauga
Sistrurus catenatus catenatus, Eastern Massasauga
Sistrurus catenatus edwardsii, Desert Massasauga
Sistrurus catenatus tergerminus, Western Massasauga
Sistrurus miliarius, Dusky Pigmy Rattlesnake
Sistrurus miliarius barbouri, Dusky Pigmy Rattlesnake
Sistrurus miliarius miliarius, Carolina Pigmy Rattlesnake
Sistrurus miliarius streckeri, Western Pigmy Rattlesnake
LITERATURE CITED
Alvarado-Díaz, J. & J.A. Campbell. 2004. A new montane rattlesnake (Viperidae) from Michoacán, Mexico. Herpetologica 60(2): 281-286.
Ashton, K. G. & de Queiroz, A. 2001. Molecular Systematics of the western rattlesnake Crotalus viridis (Viperidae) with comments on the utility of the D-Loop in phylogenetic studies of snakes. Molecular Phylogenetics and Evolution 21(2): 176-189.
Campbell, Jonathan A. & Flores-Villeta. 2008. A New Long-Tailed Rattlesnake (Viperidae) from Guerrero, Mexico. Herpetologica 64 (2): 246-257.
Campbell, Jonathan A. & Lamar, William W. 2004. The Venomous Reptiles of the Western Hemisphere. Comstock Publishing, Ithaca & London.
Clark, A. M., Moler, P. E., Possardt, E.E., Savitzky, A. H., Brown, W. S., & Bowen, B. W. 2003. Phylogeography of the Timber Rattlesnake (Crotalus horridus) Based on mtDNA Sequences. Journal of Herpetology 37 (1): 145-154.
Douglas, Michael E., Marlis R. Douglas, Gordan W. Schuett, Louis W. Porras and Blake L. Thomason. 2007. Genealogical concordance between mitochondrial and nuclear DNAs supports species recognition of the Panamint rattlesnake, Crotalus mitchellii stephensi. Copeia. 2007 (4): 920-932.
Douglas, Schuett, Porras, & Holycross. 2002. Phylogeography of the Western Rattlesnake (Crotalus viridis) Complex, With Emphasis on the Colorado Plateau. Pp. 11-50, Biology of the Vipers. Eagle Mountain Publishing, Eagle Mountain, Utah.
Klauber, Laurence M. 1972. Rattlesnakes: Their Habits, Life Histories, and Influence on Mankind, 2nd edition. University of California Press, Berkeley & Los Angeles.
Pisani, G. R., Collins, J. T., & Edwards, S. R. 1972. A re-evaluation of the subspecies of Crotalus horridus. Transactions of the Kansas Academy of Science, 75:255-263.
Pook, C. E., W. Wûster & R. S. Thorpe. 2000. Historical biogeography of the western rattlesnake (Serpentes: viperidae: Crotalus viridis), inferred from mitochondrial DNA sequence information. Molecular Phylogenetics and Evolution, 15: 269-282.
Rubio, Manny. 1998. Rattlesnake: Portrait of a Predator. Smithsonian Press, Washington & London.
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