This is a large species of chameleon that is endemic to isolated pockets of humid primary forest in eastern and northern Madagascar.
It is listed on CITES Appendix II, meaning that trade in this species is regulated.
They are the largest chameleons in the world (usually considered the largest by weight, or second-largest after the Malagasy Giant Chameleon by length).
C. parsonii males have ridges running from above the eyes to the nose, forming two warty horns.
There are two recognized subspecies: The widespread Calumma p. parsonii reaches up to 68 cm (27 in) in total length (including tail), about the size of a cat, and has no dorsal crest.
Calumma p. cristifer, from near Andasibe, reaches 47 cm (18 1⁄2 in), and has a small dorsal crest.
Ref: http://www.inaturalist.org/taxa/32892-Calumma-parsonii