Ctenis is one of the most common fossil cycads of the Mesozoic and likely represents a distinct, long-lived lineage only distantly related to living Cycas. The genus first appeared in the Permian and reached peak diversity during the Jurassic. Through the Cretaceous, its range contracted toward higher latitudes, and despite surviving two mass extinctions, Ctenis finally disappeared in the Eocene.

Like modern cycads, Ctenis species appear to have exhibited a variety of growth forms, from familiar palm-like trees to smaller, herbaceous types. At the Late Cretaceous Big Cedar Ridge site in Wyoming, a layer of volcanic ash preserved an open wetland ecosystem in remarkable detail. Here, a Ctenis species is preserved as a complete plant, with an underground stem and upright fronds rooted in peaty soils: evidence that it thrived in a sunny, open environment alongside ferns and other groundcover plants.