甘肃兰州海石湾中侏罗世Coniopteris nikaensis的大化石及原位孢子特征

Comparison of the in situ spores of selected Coniopteris species from the Middle Jurassic of Haishiwan, Lanzhou, Gansu

本文对采集于甘肃省兰州市海石湾镇中侏罗统窑街组的一块真蕨类化石进行了系统描述。当前标本最显著的特征是,小羽片分裂2~3次,相邻羽片相互接触或略叠覆,同时保留有完整的实羽叶,通过与前人已报道的蕨叶、叶脉、羽片、小羽片分裂的程度及裂片形状等特征的对比分析,发现其与Coniopteris nikaensis的基本特征完全符合,可明确该化石植物为C. nikaensis,属于窑街盆地的首次报道。经过实验分析,揭示了C. nikaensis的原位孢子基本特征:孢子三缝,赤道轮廓亚三角形,三边微凹,顶角钝圆,直径平均约35μm;射线较窄且平直,具微弱发育的唇,长度约为孢子体半径的3/4或更长;外壁薄,表面光滑。本研究为完善窑街盆地古植物群面貌提供了新材料,窑街盆地和宝积山盆地相较伊犁盆地更适宜Coniopteris的生长。

This paper systematically describes a true fern fossil collected from the Middle Jurassic Yaojie Formation in the Haishiwan area of Lanzhou, Gansu Province. The most striking feature of the current specimen is that the pinnae are split 2~3 times, and the adjacent pinnae are in contact with each other or slightly overlapped, while the intact pinnae remains intact. Through comparative analysis with the previously reported fern leaves, leaf veins, pinnae, pinnae splitting degree and lobe shape and other characteristics, it is found that it is completely consistent with the basic characteristics of Coniopteris nikaensis. It is clear that the fossil plant is C. nikaensis, which is the first report of the Yaojie Basin. After experimental analysis, the basic characteristics of in situ spores of C. nikaensis were revealed: spores with three slits,sub-triangular equatorial outline, slightly concave three sides, obtuse corners, and an average diameter of about 35 μm;the rays are narrow and straight, with weak rays developed lip, about 3/4 the radius of sporophyte or longer;outer wall thin, surface smooth. This study provides new materials for improving the paleoflora of the Yaojie Basin. Compared with the Yili Basin, the Yaojie Basin and the Baojishan Basin are more suitable for the growth of Coniopteris.