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Thyrsopteridaceae A family of tree-ferns of ancient origin, included by some authors with other tree-ferns in the Cyatheaceae. They have marginal gradate sori, which in Thyrsopteris are produced on specialized fertile pinnae, and they also have cup-like indusia. In Cibotum, the sori are on the margins of ordinary pinnae and have a 2-lipped indusium. There are 3 genera. Thyrsopteris, with only one species, T. elegans, is endemic (see ENDEMISM) to Juan Fernandez and seems to be a very ancient relict. Cibotum has 12 species and Culcita 7 species. Both are widespread in tropical and subtropical forests.