Thirty years ago Ceratopteris cornuta was a broad leaved plant where the leaves only got indented like oak leaves even when they were large. At that time cornuta was not a common plant, but was sometimes available. The common Ceratopteris then was called C. thalictroides.
Today, most people are calling the old thalictroides, C. cornuta. The name, thalictroides, has migrated to a form that has more filely divided leaves than the old thalictroides.