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Ginkgoales |
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Ginkgoales [‚giŋ·kō′ā·lēz]
(botany) An order of gymnosperms composing the class Ginkgoopsida with one living species, the dioecious maidenhair tree (Ginkgo biloba). Ginkgoales an order of gymnospermous plants comprising more than ten genera. Some of these genera belong to the family Ginkgoaceae; the systematic position of the remaining genera is unclear. In contemporary flora Ginkgoales is represented by only one species, the ginkgo, or “living fossil.” As fossils, Ginkgoales begin in the Permian period and reach their height in the Jurassic period and the first half of the Cretaceous; by the beginning of the late Cretaceous period, Ginkgoales were dying out. They grew chiefly in the northern hemisphere, primarily in Asia, in regions with a moderate climate. Some of the genera that were included in this group until recently— Czekanowskia and Phoenicopsis —have now been found to be a separate order of gymnosperms— Czekanowskia. Ginkgoales were probably deciduous trees. Dichotomous venation and the absence of central veins were characteristic of the leaves. REFERENCEOsnovy paleontologii: Golosemennye i pokrytosemennye. Moscow,1963.V. A. SAMYLINA Want to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit the webmaster's page for free fun content. |
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