How did cycadeoids differ from living cycads?

While cycadeoids (order Bennettitales) and modern cycads share a superficial resemblance—both possessing sturdy, pinnate leaves and often armored trunks—they are distinguished primarily by their reproductive structures.123

The most significant differences include:

• Cone Arrangement: Modern cycads typically bear a few large cones at the tips of their stems. In contrast, cycadeoids produced numerous smaller, often flowerlike cones embedded directly into the trunk among the leaf bases.213
• Reproductive Anatomy: Cycadeoid cones were often bisexual, containing both pollen-bearing organs and ovules within the same structure, sometimes surrounded by petal-like bracts. This arrangement is distinct from the unisexual cones of living cycads.13
• Pollination: While modern cycads are typically insect-pollinated, evidence suggests that many cycadeoid cones remained closed at maturity, likely resulting in self-pollination.1

Although their complex, flowerlike reproductive structures once led some scientists to link them to angiosperms, cycadeoids are now understood to have borne "naked" gymnospermous ovules and are not considered ancestors of true flowering plants.13