''Ginkgo yimaensis'' is an extinct

ginkgo ''Ginkgo'' is a genus of non-flowering seed plants. The scientific name is also used as the English name. The order to which it belongs, Ginkgoales, first appeared in the Permian, 270 million years ago, and is now the only living genus within ...

species in the family

Ginkgoaceae The Ginkgoaceae is a family of gymnosperms which appeared during the Mesozoic Era, of which the only extant representative is ''Ginkgo biloba'', which is for this reason sometimes regarded as a living fossil A living fossil is an extant tax ...

. It is a

gymnosperm The gymnosperms ( lit. revealed seeds) are a group of seed-producing plants that includes conifers, cycads, ''Ginkgo'', and gnetophytes, forming the clade Gymnospermae. The term ''gymnosperm'' comes from the composite word in el, γυμνό� ...

, first described by Zhou and Zhang.

Description

''Ginkgo yimaensis'' differs from the extant '' G. biloba'' only slightly. The

leaves A leaf (plural, : leaves) is any of the principal appendages of a vascular plant plant stem, stem, usually borne laterally aboveground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", wh ...

were deeply divided, resembling closer the sucker shoots and seedling leaving of ''G. biloba''. The

seeds A seed is an embryonic plant enclosed in a protective outer covering, along with a food reserve. The formation of the seed is a part of the process of reproduction in seed plants, the spermatophytes, including the gymnosperm and angiosperm pl ...

were also borne on individual stocks, unlike ''G. biloba'' which forms seeds

sessile Sessility, or sessile, may refer to: * Sessility (motility), organisms which are not able to move about * Sessility (botany), flowers or leaves that grow directly from the stem or peduncle of a plant * Sessility (medicine), tumors and polyps that ...

. The size of the seeds from specimens has ranged 10-15 mm for length and 8-12 mm for width. ''G. yimaensis'' also had pedicels 15-16 mm in length. The megaspore membrane of ''G. yimaensis'' and ''G. biloba'' are similar. However, it appears ''G. biloba'' has developed structurally beyond that of ''G. yimaensis,'' possibly by

peramorphosis In evolutionary developmental biology, heterochrony is any genetically controlled difference in the timing, rate, or duration of a developmental process in an organism compared to its ancestors or other organisms. This leads to changes in the si ...

means.

Distribution

Material of ''Ginkgo yimaensis'' has been found in the Yima Formation of

Henan Henan (; or ; ; alternatively Honan) is a landlocked province of China, in the central part of the country. Henan is often referred to as Zhongyuan or Zhongzhou (), which literally means "central plain" or "midland", although the name is al ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

, dating back to the

Middle Jurassic The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174.1 to 163.5 million years ago. Fossils of land-dwelling animals, such as dinosaurs, from the Middle Jurassic are relatively rare, but geological formations co ...

References

yimaensis Prehistoric trees Plants described in 2003 {{jurassic-plant-stub