Cycads and the extinct Cycadeoids (Bennettitales) are closely related gymnosperms. The basic difference between the two is that cones occur at the apex top of the stem in living
cycads [Figure 1], but are embedded among the leaf bases in cycadeoids [Figure 2].
Cycadeoids are easily recognized by the diamond-shaped leaf bases of the trunk. In many well-preserved specimens, you’ll see the cones of a Cycadeoid among the leaf bases.
Figure 2. Cycadeoidalean structure (from Tidwell, 1998)
