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(division Lycopodiophyta or Lycophyta), any spore-bearing vascular plant that is one of the club mosses and their allies, living and fossil. Present-day lycophytes are grouped in 6 genera (some botanists divide them into 15 or more): Huperzia, Lycopodiella, and Lycopodium, the club mosses or "ground pines"; Selaginella, the spike mosses; the unique tuberous plant Phylloglossum; and Isoetes, the quillworts. There are more than 1,200 species, widely distributed but especially numerous in the tropics. Representative extinct genera are Lepidodendron and Sigillaria, which were tree lycophytes, and Protolepidodendron, a herbaceous Lycopodium-like plant. Lycophytes are known from rocks of the Devonian Period (beginning 416 million years ago) and perhaps of the Silurian (as many as 444 million years ago). The remains of Lepidodendron and other extinct lycophytes form most of the great coal beds of the world