Plenasium xiei sp. nov. from the Cretaceous of Northeast China: Additional evidence for the longevity of osmundaceous ferns
Plenasium xiei sp. nov. from the Cretaceous of Northeast China: Additional evidence for the longevity of osmundaceous ferns
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DOI：
10.1111/jse.12532
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发表时间：
2019-09
影响因子：
3.7
通讯作者：
Ye‐Ming Cheng;Fengxiang Liu;N. Tian;Yue-Gao Jin;Tong‐Xing Sun
中科院分区：
文献类型：
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作者：
Ye‐Ming Cheng;Fengxiang Liu;N. Tian;Yue-Gao Jin;Tong‐Xing Sun
紫薇科一新种，Plenasium xiei sp. 11月，本文描述的是中国东北白垩纪。这里检查的标本代表了欧亚大陆现存的Plenasium属基于根茎化石的最早明确记录。根茎由带有叶柄基部外套膜和不定根的中央茎组成。茎含有外管管中柱和双层皮层。 C 形叶子痕迹在与石碑分离的位置有两个原木质部束。髓是异质的。实质内皮质比厚壁外皮质薄。分叶厚壁组织带出现在茎木质部束的近轴侧、叶迹的凹处以及沿叶柄基部维管束的近轴侧。在远端叶柄部分，厚壁组织带在横向视图中分裂成几组。厚壁组织环是异质的，具有厚壁纤维的背面厚壁组织弧。叶柄内皮层和托叶翼中出现许多厚壁纤维的厚壁组织束。这些化石为至少在白垩纪晚期现代Plenasium亚属的存在提供了明确的证据，证明了这个现存亚属的长寿。总而言之，Plenasium的叶和根茎化石记录表明，该属从早白垩世到新生代早期广泛分布于北美和欧亚大陆，随后在新生代晚期将范围限制在欧亚大陆。现存的 Plenasium 物种仅来自东亚和东南亚。
A new species of the Osmundaceae, Plenasium xiei sp. nov., is herein described from the Cretaceous of Northeast China. The specimens examined here represent the earliest unequivocal record of the extant genus Plenasium in Eurasia based on fossil rhizomes. The rhizome consists of a central stem with a mantle of petiole bases and adventitious roots. The stem contains an ectophloic‐dictyoxylic siphonostele and a two‐layered cortex. The C‐shaped leaf trace bears two protoxylem bundles at the point of separation from the stele. The pith is heterogeneous. The parenchymatous inner cortex is thinner than the sclerenchymatous outer cortex. Lobed sclerenchyma bands occur at the adaxial sides of the stem xylem strands, in the concavity of the leaf trace, and along the adaxial side of the vascular bundles of the petiole base. In distal petiole portions, the sclerenchyma band splits into several groups in the transverse view. Sclerenchyma rings are heterogeneous with an abaxial sclerenchymatous arc of thick‐walled fibers. Numerous sclerenchyma strands of thick‐walled fibers appear in the petiolar inner cortex and the stipular wing. These fossils provide unambiguous evidence for the existence of subgenus Plenasium of modern Plenasium by at least the Late Cretaceous, demonstrating the longevity of this extant subgenus. Altogether the leaf and rhizome fossil records of Plenasium indicate that this genus was widely distributed across North America and Eurasia from the Early Cretaceous to the Early Cenozoic, followed by a range restriction to Eurasia in the Late Cenozoic. Extant Plenasium species are only known from East and Southeast Asia.