Similarities in ovule size and structure and some other features have suggested to some that cycads might be related to medullosan seed ferns. Several megasporangia are known from Carboniferous and Permian times that have been related to cycads. Recent Permian finds from China with modern-lookng megasporangiate cones demonstrate that the old idea of reduction and aggregation in cycad cone evolution is no longer believable. You can tell foliage of cycads and cycadeoids apart by details of their leaf cuticles. Cuticle is thin on guard cells and stomata are parallel to veins.
Epidermal cells tend to be straight-margined.
Cycadeoid foliage has syndetochelic stomata, where guard cells and subsidiaries are from the same initials, cuticle on guard cells is thick and stomata are at right angles to veins. Epidermal cells tend to be wavy-margined. The concepts of haplocheilic and syndetochelic have also been used in relation to other seed plants. Cycadeoids are usually reconstructed as having a short stout trunk, although the older forms may have had more variation in plant habit. Cycadeoids are particularly interesting to the question of angiosperm origins because of the organization of their reproductive structures and the fact that they can be bisporangiate.