Bennettitales †

Plants with cycad-like form; flower-like reproduction

The Bennettitaleans are a seed-bearing, cycad-like group from the Mesozoic Era. They were originally mistaken for cycads because of their growth form, but their reproductive structures and stomatal structure make them more related to flowering plants. There are two groups: the cycadeoids (stout trunks and bisporangiate reproductive structures), and Williamsonia and Williamsoniella (slender, branching trunks and either bisporangiate or monosporangiate strobili). These reproductive structures are quite flower-like: sterile petal-like bracts, with a whorl of microsporophylls, with ovulate receptacle in the center.

Ecology & Form

Stems

  • Short tree

  • Woody stems that is heavily armored with persistent leaf bases

  • Very cycad-like vegetatively; example of convergent evolution

Leaves

  • Pinnate and cycad-like leaves with syndetocheilic stomata (Form genus is Nilssonia)

  • Oleanane present (similar to angiosperms)

Roots

  • Unknown

Reproductive Structures

  • Bisexual seed-cones that are flower-like

    • Outermost sterile bracts similar to sepal-like structures

    • Possible colorful petal-like structures

      • May have attracted and been pollinated by early invertebrates

    • Microsporophylls are pinnate fronds with pollen sacs

    • Ovulate structure

      • Ovules alternate with scales on ovulate receptacle

      • Reminiscent of angiosperm carpal (may be too derived to be ancestral to angiosperms)

    • Ovules

      • Reduced gametophyte

      • Rapid fertilization and embryogenesis after pollination

Geologic Age

Additional Resources