The Permian Peltasperm Radiation: Evidence from the Southwestern United States
The Permian Peltasperm Radiation: Evidence from the Southwestern United States
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发表时间：
2005
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通讯作者：
W. DiMichele;H. Kerp;M. Krings;D. Chaney
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作者：
W. DiMichele;H. Kerp;M. Krings;D. Chaney
Peltaspermales 是一组蕨类植物或“种子蕨类植物”，具有蕨类植物的复叶（叶状体），也带有种子。历史上，皮子植物被认为是中生代种子蕨类植物的几个类群之一，最近被证明在二叠纪热带地区分布广泛且丰富，至少早在石炭纪末期就出现了。该组包括许多属，其中大多数分布在美国西南部，这是本报告的重点。祖先亚群似乎是 callipterids，以 Autunia 属和 Rhachiphyllum 属为代表。衍生的叶类群包括comioids（Comia和一个未描述的属）、supaioids（Supaia、Glenopteris、cf. Brongniartities，也许还有几个未描述的属；该类群在分类学上是“困难的”）。北美巨蕨科的几个属也很可能归属于Peltaspermales（Gigantopteridium、Lonesomia、Evolsonia、Delnortea，以及根据脉络与中国分类群等同的三个属，但事实上，它们可能是不同的，Cathaysiopteris、Zeilleropteris 和 Gigantonoclea，以及至少一个肯定出现在中国的新属，它被描述为“Gigantopteridium”marginervum）。所有这些叶子形式都与生殖器官 Autunia (= Sandrewia) 或 Peltaspermum 相关。该类群在北美洲西南部的丰富性和多样性表明了盾子植物的广泛和早期辐射，在此期间它们成为二叠纪低地热带地区的生态优势。 67
The Peltaspermales are a group of pteridosperms or "seed ferns," plants with fern-Uke, compound leaves (fronds) that also bear seeds. Historically thought to be one of several groups of exclusively Mesozoic seed-ferns, the peltasperms have proven more recently to be widespread and abundant in the Permian tropics, appearing at least as early as latest Carboniferous. The group includes a number of genera, most of which occur in the southwestern United States, which is the focus of this report. The ancestral subgroup appears to be the callipterids, represented by the genera Autunia and Rhachiphyllum. Derived foliage taxa include the comioids (Comia and an undescribed genus), the supaioids (Supaia, Glenopteris, cf. Brongniartities, and perhaps several undescribed genera; this group is taxonomically "difficult"). Several genera of North American gigantopterids also most likely are assignable to the Peltaspermales (Gigantopteridium, Lonesomia, Evolsonia, Delnortea, and three genera equated with Chinese taxa on the basis of venation but that, in fact, may be distinct, Cathaysiopteris, Zeilleropteris, and Gigantonoclea, and at least one new genus certainly occurring in China where it was described as "Gigantopteridium" marginervum). All of these foliage forms are associated with the reproductive organs Autunia (= Sandrewia) or Peltaspermum. The abundance and diversity of this group in southwestern North America indicates an extensive and early radiation of the peltasperms, during which they became ecological dominants in the Permian lowland tropics. 67