Charles Darwin coined the term “living fossil” in The Origin of Species to describe organisms that are little changed from their ancestors. The traits they possess have enabled them to survive changing conditions, or they exist in pockets of habitat that have remained largely unchanged. Among the living fossils found at the Zoo are ancient plants that have existed since dinosaurs roamed the earth—and longer.
Though cycads superficially resemble both palms and ferns, they are actually more closely related to conifers such as pines. These plants are tougher and spinier than any fern and most barbed palms, equipped with defenses that helped them avoid being eaten by giant herbivorous dinosaurs such as Stegosaurus and Triceratops. The Zoo’s cycad garden (in front of Zoo Grill) includes species from Africa and the Americas. Extremely slow growing and slow to reproduce, many today are endangered in the wild due to habitat loss, though some species have become popular landscaping plants thanks to domestic propagation.
Across from the cycad garden, next to the administration buildings, is a maidenhair tree (Ginkgo biloba). (A ginkgo grove can also be found at the Zoo’s Papiano Play Park.) Previously known in the West only by fossil records dating back 270 million years, these beautiful trees were widely believed to have vanished along with the dinosaurs, but in 1691, a concealed grove was discovered growing in Japan by the German physician and naturalist Engelbert Kaempfer. He later brought seeds to Europe where they were easily propagated and have since become popular ornamental trees.
The dawn redwood (Metasequoia glyptostroboides) was also believed to be long extinct when a relict grove was discovered in a remote valley in China. These living trees were almost identical to fossil remains carbon dated at 90 million years in age. A 10,000-mile trek led by paleobotanist Dr. Ralph Chaney of the University of California, Berkeley in 1948 brought seed back to the U.S. All the dawn redwoods alive today (including those at the Zoo) originate with that expedition. Superficially, dawn redwood trees resemble California coast redwoods, though they are deciduous and drop their needles seasonally. They are endangered in the wild.
Ferns are so common (there are more than 11,000 species worldwide) that it’s easy to overlook their remarkable history, which stretches back about 400 million years. Ferns predated flowering plants and were the dominant botanical life form during the Carboniferous era 360 to 286 million years ago when flying insects and reptiles first appeared. Large tree ferns (native to Australia) are found throughout the Zoo as are our native California sword ferns.