Lycopodiopsida is a class of plants often loosely grouped as the fern allies Fern ally is a general term covering a somewhat diverse group of vascular plants that are not flowering plants and not true ferns. Like ferns, these plants disperse by shedding spores to initiate an alternation of generations, and includes the clubmosses. Lycopodiopsida traditionally included all the clubmosses, including Selaginella and Isoetes. However, subdivisions within the Division Lycopodiophyta The Division Lycopodiophyta is a tracheophyte subdivision of the Kingdom Plantae. It is the oldest extant (living) vascular plant division at around 410 million years old,:99 and includes some of the most "primitive" extant species. These species reproduce by shedding spores and have macroscopic alternation of generations, although some are now considered ancient enough to warrant higher-level separation in accordance with cladistics Cladistics is a form of biological systematics that classifies species of organisms into hierarchical monophyletic groups. It can be distinguished from other taxonomic systems, such as phenetics, by its focus on shared derived characters (synapomorphies). Previous systems usually employed overall morphological similarity to group species into.

Clubmosses are thought to be structurally similar to the earliest vascular plants Vascular plants are those plants that have lignified tissues for conducting water, minerals, and photosynthetic products through the plant. Vascular plants include the ferns, clubmosses, flowering plants, conifers and other gymnosperms. Scientific names for the group include Tracheophyta and Tracheobionta, but neither name is very widely used.[, with small, scale-like leaves, homosporous spores In biology, a spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many bacteria, plants, algae, fungi and some protozoans. A chief difference between spores and seeds as dispersal units is that spores have very little stored borne in sporangia A sporangium is a plant, fungal, or algal structure producing and containing spores. Sporangia occur in angiosperms, gymnosperms, ferns, fern allies, bryophytes, algae, and fungi. Their spores are sometimes called sporangios