亚轮生奇异蕨(Adoketophyton subverticillatum)在贵州都匀泥盆系蟒山群的发现及其意义

Adoketophyton subverticillatum (Li et Cai) Li et Edwards (亚轮生奇异蕨)是云南早泥盆世坡松冲植物群中颇具代表性的、研究较为详细的一种植物, 目前对其整体形态特征和解剖结构都有较深入的认识。本文通过系列针修法, 将采自贵州都匀包阳剖面蟒山群下段的一块植物化石新材料归入A. subverticillatum。基于目前对 Adoketophyton时空分布的认识, 认为该属可作为早泥盆世植物群的代表分子, 并据此推断蟒山群下段的时代应为早泥盆世。Adoketophyton subverticillatum在都匀的发现, 表明贵州都匀蟒山群中的植物与云南坡松冲植物群在属、种一级上存在扩散与交流现象。Adoketophyton以及其他相关植物的研究表明, 在高大气CO₂浓度的早泥盆世, 叶性结构如孢子叶、苞片、枝叶复合体等已广泛分布于华南板块。

The discovery of Adoketophyton subverticillatum from the Devonian Mangshan Group of Duyun, Guizhou Province and its significance

Adoketophyton subverticillatum (Li et Cai) Li et Edwards is one of the representative and well-known plants in the Early Devonian Posongchong flora of Yunnan, and its external morphology and anatomy have been described in detail. One specimen collected from the lower part of the Mangshan Group at the Baoyang section of Duyun, Guizhou Province is assigned herein to A. subverticillatum, based on features revealed by serial dégagement. The specimen, broken at both ends, is ca. 19.3 mm long, and shows a fertile axis comprising of sporophylls and sporangia. The fertile axis is slender, ca. 0.9 mm wide. The fan-shaped sporophylls, 6.2 mm in length and 6.4 mm in maximum width when complete, are oppositely and decussately inserted on the fertile axis to form four vertical rows. An incomplete sporangium reaches up to 4.1 mm high and 1.1 mm wide. The temporal and spatial distribution of Adoketophyton indicates that this genus is a representative element of the Early Devonian floras, thus suggesting an Early Devonian age for the lower part of the Mangshan Group. The discovery of A. subverticillatum in Duyun confirms the dispersal and interrelationship at the genus and species levels between the Posongchong flora of Yunnan and plants from the Mangshan Group of Duyun, Guizhou. The studies of Adoketophyton and other related taxa suggest that leafy structures, such as sporophylls, bracts, and branch-leaf complexes, were widespread in the South China Block during the Early Devonian, when the atmospheric CO₂ level was high.