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- Title
The pollen cones of Ginkgo from the Early Cretaceous of China, and their bearing on the evolutionary significance.
- Authors
Xiu-Qun Liu; Cheng-Sen Li; Yu-Fei Wang
- Abstract
A well-preserved pollen cone of the genus Ginkgo was found in the Yixian Formation (Early Cretaceous) of Liaoning Province, China, and is described as the new species Ginkgo liaoningensis. The pollen cone, catkin-like, consists of a main axis bearing scales at its base and spirally arranged sporophylls bearing 3-4 (-2) oval or elliptical sporangia. The sporangia are pendulous and dehiscent by a longitudinal slit. The mature pollen grains are monocolpate and elongate-elliptical, and the juvenile pollen grains are found in the tetrad stage. The characteristics of G. liaoningensis are very similar to those of the living Ginkgo biloba, but the sporophylls of G. liaoningensis bear 3-4 (-2) sporangia, whereas those of G. biloba bear mostly two sporangia. G. liaoningensis differs from fossil cones of Ginkgo huttoni from the Jurassic of Yorkshire, UK, and an unnamed specimen of Ginkgo from the Upper Cretaceous of Alberta, Canada, in the size and number of sporangia. The comparison between G. liaoningensis (fossil) and G. biloba (living) supports the reduction hypothesis of ovule organs in Ginkgo, with the number of sporangia having experienced the process of reduction from three or four to two since the Early Cretaceous.
- Subjects
GINKGO; PALYNOLOGY; POLLEN; POLLINATION; BIOLOGICAL evolution; GYMNOSPERMS
- Publication
Botanical Journal of the Linnean Society, 2006, Vol 152, Issue 2, p133
- ISSN
0024-4074
- Publication type
Article
- DOI
10.1111/j.1095-8339.2006.00547.x