By the time dinosaurs ruled the world, cycads were already fairly widespread, having made their appearance in the late Paleozoic era. The prehistoric plants provided food for many of the giant plant-eaters and managed to adapt and survive through the world's drastic climate changes to become even more widespread in our era.


Today, the young leaves and seeds of a number of cycad species continue to provide food for animals, although most are poisonous for humans without processing to remove their natural alkaloids. When cooked, however, the starch from some cycad stems and seeds is not only edible but has also been an important human food source in times of famine. With 82 taxa and many mature specimens, the San Diego Zoo has one of the best cycad collections in the world, including 29 species that are conservation worthy.