| Autor: |
Yong Yang, Bao-Yin Geng, Dilcher, David L., Zhi-Duan Chen, Lott, Terry A. |
| Předmět: |
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| Zdroj: |
American Journal of Botany; Feb2005, Vol. 92 Issue 2, p231-241, 11p, 1 Diagram, 1 Chart |
| Abstrakt: |
Detailed investigations on Lower Cretaceous Ephedra L. fossils (Gnetopsida) reveal morphological characters similar to those of extant Ephedra rhytidosperma Pachomova, including articulate branches with many fine longitudinal striations, a dichasial branching pattern, uni- or bi-ovulate cones with paired bracts, cones terminal on branchlets, and seeds with a short, straight micropylar tubes, covered by numerous regular and prominent transverse laminar protuberances. Fossils are similar to extant E. rhytidosperma reproductive organs but differ in some vegetative structures and are described and discussed here as Ephedra archaeorhytidosperma Y. Yang et al. Because E. rhytidosperma is currently considered one of the most specialized members in Ephedra L. section Pseudobaccatae Stapf, the occurrence of E. archaeorhytidosperma in the Yixian Formation suggests that Ephedra L. was perhaps a more diverse genus in the Lower Cretaceous. Perhaps the evolution and diversity of Ephedra L. was already in place by the Lower Cretaceous and certainly before the end of the Mesozoic. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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