甘肃永昌乌拉尔世几种楔叶植物的发现及古地理意义

为了更好地了解晚古生代楔叶属的物种多样性及形态演化,通过对化石宏观形态的研究以及与相似化石种的对比,确定甘肃永昌太原组中几种楔叶植物化石的分类位置。本文共鉴定楔叶植物化石2属5种,其中包括营养叶和繁殖器官。基于这些楔叶属的新材料,对椭圆楔叶以及马齿楔叶的茎轴表面纵纹、叶片分裂次数等特征进行修订。同时报道楔叶穗属一新种Bowmanites yongchangensis sp. nov.。结合该属在晚古生代的古地理分布情况,表明在乌拉尔世早期该研究区内楔叶属植物呈现出较高的物种多样性,并推测该属植物的起源时间不晚于晚泥盆世法门期,在维宪期由华南地区传入华北地区后,于宾夕法尼亚亚纪晚期传入龙首山地区所在的阿拉善地块。

DISCOVERY OF SEVERAL SPHENOPHYLLUM FROM CISURALIAN IN YONGCHANG,GANSU AND ITS PALEOGEOGRAPHICAL SIGNIFICANCE

In order to study the taxonomic diversity and morphology evolution of Sphenophyllum in the Late Paleozoic, several sphenophytes fossils, collected from Taiyuan Formation in Yongchang County, Gansu, were studied by comparing their morphological characters with similar fossil species. A total of 5 species within 2 genera of sphenophytes fossils were identified in this study, including vegetative leaves and reproductive organs. Based on these new specimens of Sphenophyllum, some characteristics (longitudinal lines present on stem surface, the number of leaf divisions and leaf veins, etc.) of Sphenophyllum kawasakii Stockm. et Mathand Sphenophyllum oblongifolium (Unger) Barthel were modified. A new species of Bowmanites yongchangensis sp. nov. was also reported. According to the palaeogeographic distribution of Sphenophyllum plants in the Late Paleozoic, Sphenophyllum reported in the early Cisuralian from the study area showed a high diversity. And it can also be speculated that Sphenophyllum plants originated no later than the late Devonian, and spread into North China from Southern China during the Visean. Finally, in the late Pennsylvania, Sphenophyllum migrated from North China into the Longshoushan Mountain area in Alashan Terrane.