Morphology and age of Yimaia (Ginkgoales) from Daohugou Village, Ningcheng, Inner Mongolia, China

New ginkgoalean ovulate organs of Yimaia type were found in the fossil-bearing bed of the village of Daohugou, Ningcheng, Inner Mongolia. They generally resemble other species of Yimaia and some detached seeds described under the morphogeneric name Allicospermum from the Lower and Middle Jurassic in shape and size of ovules, but are markedly distinguished by the cuticular structure of the integument. The ultrastructure of the megaspore membrane and the associated leaves also differ from those known in comparable taxa. Ginkgoalean leaves found in the Daohugou bed are mainly of the Ginkgoites type, some of which are still attached to the shoots. They may be classified in three morphotypes. Leaves of Ginkgoites Morphotype 1, which are most abundant and closely associated with Yimaia, probably belong to the same plant. The presence of the Jurassic element Yimaia supports the opinion of some invertebrate palaeontologists that the Daohugou bed is of Jurassic (most probably mid Jurassic) age. In floristic composition, the Daohugou plant assemblage differs from the early Cretaceous Jehol flora, but closely resembles the Middle Jurassic flora of northeast China.