Abstract：
: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.
journal_name
Am J Botjournal_title
American journal of botanyauthors
Yang Y,Geng BY,Dilcher DL,Chen ZD,Lott TAdoi
10.3732/ajb.92.2.231subject
Has Abstractpub_date
2005-02-01 00:00:00pages
231-41issue
2eissn
0002-9122issn
1537-2197pii
92/2/231journal_volume
92pub_type
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journal_title：American journal of botany
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更新日期：1999-04-01 00:00:00
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