An Early Cretaceous Ginkgo ovule-bearing organ fossil from Liaoning, Northeast China and its evolutionary implications

摘要

Ginkgo is a very important gymnospermous genus that has only one surviving species, Ginkgo biloba L. As a so-called "living fossil", wild Ginkgo was found only in China, but it once flourished well and had a world-wide distribution in the Mesozoic. The earliest Ginkgo has been known from the Middle Jurassic, based on ovule-bearing organs~([1]). In the Jurassic and Early Cretaceous, Ginkgo was one of the dominant gymnosperms in floras and possibly one of the coal-forming plants in North China. During the Early Tertiary, it reduced to a circumpolar distribution in the North Hemisphere~([2,3]); only a few reported from the South Hemisphere~([4]). From the Pliocene onwards, the Ginkgoales has been represented by the extant monotypic "living fossil" Ginkgo biloba~([2]).