In the past, cycads attained a global distribution, extending over the Earth from Alaska and Siberia to the Antarctic. Fossils are known from every continent, a feat that was possible because of the generally warmer climate of the Mesozoic, and higher moisture than today. The family Stangeriaceae , which today is restricted to small portions of Africa and Australia, existed in Argentina and the British Isles. The fossil depicted at right is a cycad-like fossil leaf assigned to the genus Ptilophyllum , common in the flora of Gondwana through most of the Mesozoic. This leaf may actually belong to another group, the Bennettitales , which are very similar in their morphology to cycads, and are often difficult to distinguish from them.
Leaves are only one of the structures preserved in the fossil record.
We have also found fossilized stems, cones, and seeds, all of which help us to reconstruct the appearance and biology of these ancient plants. In addition to the eleven living genera, many of which are known as fossils, there are 19 extinct cycad genera known only as fossils.