C. complanatum is an uncommon but possibly overlooked moss shows a preference for tree fern trunks.

The leaves are arranged in three ranks with two rows of normal sized lateral leaves and a row of smaller leaves on the underside of the stem. The lateral leaves are elliptic to oblong-obovate and the leaf nerve extends to just under the leaf apex.

C. complanatum is similar to Hymenodon pilifer but lacks the long hairpoint of that species.