Sources vary on how many species the genus contains. Some consider the rubber boa, C. bottae, to be the sole member of the genus. In addition, some experts consider the southern rubber boa, C. umbratica to be a subspecies of C. bottae. Although the Calabar python, Calabaria reinhardtii has been included in Charina, recent phylogenetic analyses based on DNA have shown that it does not belong to this genus.
^ abcdMcDiarmid 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).
^ abWright AH, Wright AA. 1957. Handbook of Snakes. 2 volumes. Comstock Publishing Associates. (7th printing, 1985). 1105 pp. ISBN 0-8014-0463-0.
^Pyron, Robert Alexander, Frank T. Burbrink, and John J. Wiens. "A phylogeny and revised classification of Squamata, including 4161 species of lizards and snakes." BMC evolutionary biology 13.1 (2013): 93.