A new species of Adoketophyton from the Lower Devonian (Pragian) Posongchong Formation of Yunnan, China

A new species of early vascular plant, Adoketophyton parvulum sp. nov., is described from the Lower Devonian (Pragian) Posongchong Formation of Yunnan, China. The plant is composed of main axes, lateral vegetative branches and isotomous or anisotomous fertile axes. The vegetative axes branch isotomously or pseudomonopodially in three dimensions, with some laterals ending in terminal circinately coiled tips. K-shaped branching and tubercles are preserved. Terminal strobili consist of four vertical rows of fertile units, arranged in opposite and decussate pairs. Each fertile unit comprises a fan-shaped sporophyll and a sporangium attached adaxially by a short stalk at the base of the sporophyll. The strobili and fertile units (sporophylls and associated sporangia) of this new species are much smaller than those of the type species, Adoketophyton subverticillatum, and the ratio of heights of sporangia to sporophyll laminae in the two species shows a large discrepancy. The affinity and evolution of Adokerophyron are discussed. The various leaf-like appendages in plants reported from the Early Devonian of South China are considered a phenomenon of convergent evolution. (C) 2011 Elsevier B.V. All rights reserved.