C. truncatus is the only armadillo whose dorsal shell is almost separated from the body. The separate plate at the rear is securely attached to the pelvic bones. The spatula-shaped tail projects from a notch at the lower edge of the rear plate. The tail cannot be raised and is dragged on the ground. The lips are horny and stiff, the nose is pointed, and the nostrils are ducted downward.
Females have two mammae.
In C. retusus head and body length is 140-75 mm and tail length is about 35 mm. The plates are whitish and yellowish brown in color and the woolly hair is whitish. The head is covered by a shield, the dorsal carapace is attached to the skin of the back for its entire extent, and the tail is partly covered with plates. The underparts are covered with woolly hair. C. retusus resembles C. truncatus but is larger, has the entire carapace attached to the body, and has a less defined head shield that lacks a posterior row of large scutes.