麻黄属植物（买麻藤目）的早期多样性：来自葡萄牙和北美早白垩世种子的证据。
Former diversity of Ephedra (Gnetales): evidence from Early Cretaceous seeds from Portugal and North America.
作者信息
Rydin Catarina, Pedersen Kaj Raunsgaard, Crane Peter R, Friis Else Marie
机构信息
Department of Palaeobotany, Swedish Museum of Natural History, Box 50007, S-104 05 Stockholm, Sweden.
出版信息
Ann Bot. 2006 Jul;98(1):123-40. doi: 10.1093/aob/mcl078. Epub 2006 May 4.
BACKGROUND AND AIMS
The extant species of the seed plant group Gnetales (Ephedra, Gnetum and Welwitschia) have been considered a remnant of a much greater, now extinct, diversity due to the pronounced differences in form and ecology among the genera. Until recently, this hypothesis has not been supported by evidence from the fossil record. This paper adds to the expanding information on Gnetales from the Early Cretaceous and describes coalified seeds from Barremian-Albian localities in Portugal and USA.
METHODS
The fossils were extracted from sediment samples by sieving in water. Adhering mineral matrix was removed by chemical treatment. Seeds were investigated using light and scanning electron microscopy. Morphology and anatomy of the seeds were documented and compared with those of extant species.
KEY RESULTS
The fossils share characters with extant Ephedra, for example papillae on the inner surface of the seed envelope and in situ polyplicate pollen grains that shed the exine during germination. They differ from extant Ephedra seeds in morphological and anatomical details as well as in their smaller size. Two new species of Ephedra are described together with one species assigned to a new genus of Gnetales. Other Ephedra-like seeds, for which pollen and critical morphological details are currently unknown, are also present in the samples.
CONCLUSIONS
These Cretaceous seeds document that key reproductive characters and pollen germination processes have remained unchanged within Ephedra for about 120 million years or more. There is sufficient variety in details of morphology to suggest that a diversity of Ephedra and Ephedra-like species were present in the Early Cretaceous flora. Their presence in Portugal and eastern North America indicates that they were widespread on the Laurasian continent. The fossil seeds are similar to seeds of Erdtmanithecales and this supports the previously suggested relationship between Erdtmanithecales and Gnetales.
背景与目的
种子植物类群买麻藤目（麻黄属、买麻藤属和百岁兰属）现存的物种，由于各属在形态和生态上存在显著差异，一直被视为一个更为庞大、现已灭绝的多样性的残余。直到最近，这一假说尚未得到化石记录证据的支持。本文补充了关于早白垩世买麻藤目的不断扩充的信息，并描述了来自葡萄牙和美国巴列姆阶 - 阿尔比阶地区的煤化种子。
方法
通过在水中筛分从沉积物样本中提取化石。通过化学处理去除附着的矿物基质。使用光学显微镜和扫描电子显微镜对种子进行研究。记录种子的形态和解剖结构，并与现存物种进行比较。
主要结果
这些化石与现存的麻黄属植物具有共同特征，例如种子包膜内表面的乳头状突起以及原位多褶花粉粒，后者在萌发时会脱落花粉外壁。它们在形态和解剖细节以及较小的尺寸方面与现存的麻黄属种子不同。描述了两个新的麻黄属物种以及一个归入买麻藤目新属的物种。样本中还存在其他类似麻黄属的种子，目前其花粉和关键形态细节尚不清楚。
结论
这些白垩纪种子证明，麻黄属植物的关键繁殖特征和花粉萌发过程在约1.2亿年或更长时间内保持不变。形态细节有足够的多样性，表明早白垩世植物群中存在多种麻黄属和类似麻黄属的物种。它们在葡萄牙和北美东部的存在表明它们曾广泛分布于劳亚大陆。这些化石种子与埃尔德曼木目种子相似，这支持了之前提出的埃尔德曼木目与买麻藤目之间的关系。
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