The genus was first erected by Lindley and Hutton in "The fossil flora of Great Britain",[2] based on material of Ctenis falcata from the Jurassic of Yorkshire.

Later, Seward,[4] Florin, and Harris[5] added details of the cuticle to the diagnosis of the genus.

Due to the leaves of Ctenis possessing characters unknown in any living cycad, Ctenis is thought to belong to an extinct lineage distinct from modern cycads, with a 2023 analysis finding that the genus was paraphyletic with respect to Dioonopsis and Pterostoma, with this group suggested to be the sister group to Cycadaceae, from which they split in the Permian period.

[6] The leaves of Ctenis are once pinnate, and the pinnae have multiple parallel veins that often anastomosize (i.e. fuse together).

[15] This suggests that at least some members of the genus inhabited wet environments with peaty soils.