Institute of Deep Time Terrestrial Ecology, Yunnan University, Kunming 650091, People's Republic of China
Research Center for Earth System Science, Yunnan University, Kunming 650500, People's Republic of China.
Biol Lett. 2017 Nov;13(11). doi: 10.1098/rsbl.2017.0456.
Today, cycads are a small group of gymnospermous plants with a limited distribution in the (sub)tropics, but they were major constituents of Mesozoic floras. Fossil leaves sporadically found in latest Carboniferous and Permian floras have putatively been ascribed to cycads. However, their true affinity remains unclear due to the lack of anatomical evidence. Virtually all modern cycads have pinnate leaves, but this type of leaf morphology is by no means unique for cycads. Pinnate leaves of Halle 1927 with well-preserved cuticles showing the epidermal anatomy are here described from the upper Permian Xuanwei Formation of Yunnan Province, Southwest China. The cuticles show a clear differentiation into costal and intercostal zones; stomata are confined to the intercostal zones on both the upper and lower leaf surfaces. The external morphology and the epidermal anatomy of these fossil leaves are closely comparable with those of extant cycads, particularly members of the family Zamiaceae.
今天，苏铁类植物是一组小型裸子植物，分布范围有限，局限于（亚热带）热带地区，但它们曾是中生代植物群的主要组成部分。在晚石炭世和二叠纪植物群中偶尔发现的化石叶子被推测为苏铁类植物的叶子。然而，由于缺乏解剖学证据，它们的真实亲缘关系仍不清楚。几乎所有现代苏铁类植物都有羽状叶子，但这种叶子形态对于苏铁类植物来说并不是独一无二的。来自中国西南部云南省上二叠统宣威组的 Halle 1927 号标本，其保存完好的表皮结构的叶表皮具有明显的羽片状，在这里被描述。这些表皮显示出明显的脊区和肋区的分化；气孔仅限于上下叶片的肋区。这些化石叶子的外部形态和表皮解剖结构与现存苏铁类植物，特别是泽米科的成员密切可比。
