The Isoetales sensu DiMichele and Bateman encompasses the former Lepidodendrales (Carboniferous arborescent lepidodendrids), Pleuromeiales (Triassic) and Isoetaceae (Mesozoic to present), and possibly some Devonian forms. These lycopsids are united by the synapomorphies of stigmarian rootlets, bipolar growth and secondary tissues. Despite recent advances we still lack an understanding of the origin, early diversification, phylogeny and degree of homoplasy within this group. As part of a new study of evolutionary patterns and diversity within the clade, we are reconstructing whole plants for two potentially informative earlier Paleozoic forms, Cyclostigma kiltorkense and the Lepidodendropsis/Protostigmaria plant, from their component vegetative and fertile remains. Our collection of Lepidodendropsis specimens from two close, stratigraphically similar sites in southwestern Virginia includes large stumps, meter-long stems of varying diameter, sometimes dichotomizing large branches, small twigs, stems with attached leaves, isolated leaves, fragments of fertile regions, sporangia, sporophylls, and spores. Branching is isodichotomous, and stems bear numerous small leaf scars arranged in low helices or pseudowhorls outlined by vertical ridges. The outer stem surface shows some attached leaves, and several decortication layers (layers at various subsurface levels through the thick bark typical of many isoetaleans) are present. Thus far, parichnos strands and ligules are unknown. Preliminary studies confirm that it is possible to deduce cortical anatomy in these compression remains by comparing different patterns of stem surfaces and leaf bases, caused by different types of secondary cortical tissues and varying degrees of decortication, to those established from permineralized forms, (e.g., Chaloneria). Stem surface/leaf base patterns have provided both phylogenetically informative characters and improved understanding of plant growth, as first discussed by Eggert. Some Lepidodendropsis stems exhibit both of the two types of leaf bases traditionally used to recognize two separate species within Virginia Lepidodendropsis, suggesting our study will significantly contribute to a better understanding of Mississippian isoetalean diversity.

Key words: Isoetalean, Lepidodendropsis/Protostigmaria, Mississippian, reconstruction