A Zosterophyllum-like plant from the Lower Devonian of Yunnan Province, China

Abstract

A new fossil plant, Wenshania zhichangensis Zhu et Kenrick, gen. et sp. nov., is described from the Lower Devonian Posonchong Formation of Yunnan Province, southwestern China. The description is based on compression fossils, which document a small herbaceous plant that closely resembles other Zosterophyllum-like fossils from the same deposits. These extinct plants are leafless, have simple dichotomous branching, and bear sporangia in rows or helices along the stem. The relationships of W. zhichangensis are discussed and some problems with the genus Zosterophyllum are highlighted. W. zhichangensis is a basal member of the zosterophyll–lycopsid clade, and this description adds to a growing body of data on the diversity of Zosterophyllum-like plants in early terrestrial floras. Data from the Posonchong Formation show that small herbaceous lycopsids and zosterophylls comprise 65% of the documented species diversity, indicating that these groups were a major component of the Lower Devonian floras of Gondwana.