An order of the Coniferopsida, one of the major gymnosperm groups. Only one species of Ginkgo survives, Ginkgo biloba. The first undoubted maidenhairs occur in Triassic rocks, and in the subsequent Jurassic Period their distribution was practically world-wide. The surviving species is restricted (in the wild) to China, and its fan-shaped leaves, with open dichotomous venation are strikingly similar to fossil Ginkgo leaves. Many fossil species are known. The earliest representative of the genus, G. digitara, is first recorded from the Middle Jurassic. The restricted geographical range, the unchanged appearance of the leaves, and the motile male sperms (otherwise known only in living seed plants in the Cycadales) have together led to the maidenhair being referred to as a living fossil. Other classifications have placed ginkgos in the class Ginkgoopsida.
Subjects: Earth Sciences and Geography.