Achlamydocarpon pingquanensis sp. nov. (Lycopsida): A Novel, Anatomically Preserved Lepidodendralean Disseminule from the Lower Permian of North China

A new species of the arborescent lycopsid disseminule Achlamydocarpon is described and diagnosed from volcaniclastic tuffs in the Lower Permian Taiyuan Formation of northern China. Achlamydocarpon pingquanensis sp. nov. comprises a large megasporangium-sporophyll unit with a dorsiventrally flattened sporangium lacking a dorsal ridge and keel, containing a single functional and three abortive megaspores, eachwith a conspicuousmassa. The pedicel has narrowly winged lateral laminae that develop upward and outward, partially enveloping the basal part of the sporangium. An elliptical xylemstrand is developed distally and is surrounded by a parichnos cavity. The sporangial wall has an outer parenchymatous layer, a middle sclerotic layer, and an inner, thick, parenchymatous layer and has a subarchesporial pad with a toothed margin. Achlamydocarpon pingquanensis does not readily conform to the previously recognized distinction between the Achlamydocarpon varius and Achlamydocarpon takhtajanii types, possessing characters belonging to both groups. This adds to a growing body of data on arborescent lycopsids from the Paleozoic Cathaysian floras and supports the systematic distinction of Cathaysian lepidodendralean plants (previously termed ‘‘Oriental lepidophytes’’) as a distinct subset of the Lepidodendrales. However, their phylogenetic position remains uncertain because of an absence of reconstructedwhole plants toenter into cladistic analyses, and thus their crown- or stem-group position within Lepidodendrales is unknown.