Abstract
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, each with a conspicuous massa. The pedicel has narrowly winged lateral laminae that develop upward and outward, partially enveloping the basal part of the sporangium. An elliptical xylem strand 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 reconstructed whole plants to enter into cladistic analyses, and thus their crown- or stem-group position within Lepidodendrales is unknown.
Original language | English |
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Pages (from-to) | 567-577 |
Number of pages | 11 |
Journal | International Journal of Plant Sciences |
Volume | 167 |
DOIs | |
Publication status | Published - 1 May 2006 |
Keywords
- Achlamydocarpon
- Lycopsida
- Permian
- Lepidodendrales
- Cathaysian flora