贵州都匀下泥盆统蟒山群Zosterophyllum australianum(澳大利亚工蕨)新材料及其古地理意义

New material of Zosterophyllum australianum from the Lower Devonian Mangshan Group in Duyun, Guizhou and its palaeogeographic implications

Zosterophyllum(工蕨属)是早期陆生植物的代表性类群之一,全球广泛分布。Z.australianum(澳大利亚工蕨)产自华南和澳大利亚,是东北冈瓦纳古植物地理区系的典型分子。文中描述了产自贵州都匀包阳剖面蟒山群中的Z.australianum新材料。该标本的孢子囊具短柄,呈椭圆形或扇形,宽2.6~4.1 mm,高可达3.9 mm,加厚带宽约0.6 mm,紧密螺旋排列形成孢子囊穗,与云南文山早泥盆世坡松冲植物群中的Z.australiaunum极为相似。依据目前对Z.australianum时代延限的认识,并结合蟒山群其他植物属种的发现(如Adoketophyton subverticillatum),推断该群下段的时代为早泥盆世布拉格期。Z.australianum在蟒山群中的发现,扩展了该植物的地理分布范围,反映出蟒山群中的植物组合与坡松冲植物群存在一定联系。

Zosterophyllum is one of the representative taxa of early land plants, and has a worldwide distribution. Z. australianum occurred in South China and Australia, and is a typical species of the Northeastern Gondwana Phytogeographic Unit. New material of Z.australianum from the Mangshan Group of the Baoyang section in Duyun, Guizhou is described here. The plant is characterized by sporangia with a short stalk, which are closely arranged forming a spike, and the sporangia are elliptical or fan-shaped, ca. 2.6~4.1 mm wide and up to 3.9 mm high, and the thickened border is ca. 0.6 mm wide. These features are closely comparable to those of Z. australianum from the Early Devonian Posongchong flora of Wenshan, Yunnan. On the basis of the temporal range of Z. australianum and other plants such as Adoketophyton subverticillatum from the Mangshan Group, the lower part of this group is suggested to be the Pragian of the Early Devonian in age. The discovery of Z. australianum from the Mangshan Group extends the geographic distribution of this species, and adds evidence to a certain relationship between the plant assemblages from the Mangshan Group and the Posongchong flora.