山西太原早二叠世山西始莲座蕨(新种)及其古植物地理学和古环境意义

Eoangiopteris shanxiensis sp.nov.from the Early Permian of Taiyuan,Shanxi and its palaeophytogeographic and palaeoenvironmental significance

报道了山西太原西山煤田早二叠世早期太原组7号煤层煤核中一种具解剖构造的、两侧对称的莲座蕨目聚合囊,这是目前为止华夏植物区已知地质时代最早的两侧对称的莲座蕨目聚合囊。经对比研究,将当前标本归入始莲座蕨属Eoangiopteris Mamay,并建立一新种:山西始莲座蕨E.shanxiensis sp.nov.。新种的主要特征:生殖小羽片至少2.6 mm宽,长度不明,中脉具一"C"形维管束。生殖小羽片明显背卷,但没有影响到聚合囊的排列。聚合囊两侧对称,长0.75～1.1 mm,宽0.35～0.55 mm,由8～12枚孢子囊构成,孢子囊侧向相互接触。聚合囊具短而明显的托,由薄壁组织包围着维管组织构成。孢子囊直径150～250μm,高550～850μm,纵切面上呈筒状,具明显的实心的顶端。孢子囊面向外的壁在中下部为2～3层细胞厚,在顶端为3～4层细胞厚,细胞近等径,壁较厚;侧壁和面向内的壁为1层细胞厚,在孢子囊中下部呈弦向伸长状,在顶端则呈径向伸长状,壁较薄。孢子数量多,可达1000粒以上,个体小,近球形,直径8～13μm,具三缝构造;孢子壁由外壁和周壁构成,外壁光滑,周壁具细颗粒纹饰。讨论了本新种的系统分类位置,很可能属于辉木科。根据欧美植物区和华夏植物区两侧对称的莲座蕨目聚合囊的分布特征探讨了本新种的古植物地理学意义,并结合7号煤层煤核中植物化石的组成特征和一些植物的生态解剖学构造简要探讨了本新种的生活环境特征。

This paper reports a kind of anatomically preserved bilaterally symmetrical marattialean synangia from the coal balls in coal seam No. 7 in the Taiyuan Formation （early Early Permian） of Xishan Coal Field, Taiyuan, Shanxi. These synangia are the earliest in the geological time in the bilaterally symmetrical marattialean synangium ever found in the Cathaysian Flora so far. Compared with other anatomically preserved bilaterally symmetrical marattialean synangia in the world, these synangia are assigned to Eoangiopteris Mamay and a new species, E. shanxiensis sp. nov., is proposed. The diagnostic characters of the new species are as follows ： The fertile pinnule is at least 2.6 mm wide, but its length is unknown because of its poor preservation. The midrib of the pinnule possesses a ＂C＂ shaped vascular bundle. The fertile pinnule is down-turned at its margin and the arrangement of the synangia is not affected. Synangia are 0. 75 - 1.1 mm in length and 0. 35 -0.55 mm in width and consist of 8 - 12 sporangia arranged in two rows along the lateral veins. Synangia bear a short and conspicuous reptaele consisting of parenehyma enclosing vascular tissue. Sporangia are elongate with a conspicuous and solid tip and are 150 -250 μm in diameter and 550 -850 μm in height. The out-facing sporangial wails are 2 -3 ceils thick in the middle and lower part and 3 - 4 ceils thick in the upper part of the sporangia and the ceils are nearly isodiametric with the slightly thickened wails. The inner-facing and lateral sporangial wails are only one cell thick and the cells are tangentially elongate in the middle and lower part and radially elongate at the upper part of the sporangia with the wails. Spores are numerous （probably more than one thousand in number）, spherical, trilete and small （8 - 13 μm in diameter） with the smooth exine and slightly granular ornamented perine. The systematic position of the new species is discussed and it belongs to Psaroniaceae with a great possibility. The paleophytogeographic significance of the new species is considered based on the distribution of the bilaterally symmetrical marattialean synangia in the Euramerican and Cathaysian floras. The environmental conditions of the new species are discussed based on the constitution of fossil plants in the coal bails and the ecological anatomic structures of some plants.