Selaginella moellendorffii is a lycophyte that is an important model organism, especially in comparative genomics. S. moellendorffii is a member of an ancient vascular plant lineage that first appeared in the fossil record some 400 million years ago. They would later form a dominant part of the world's flora during the Carboniferous period. They have a number of unusual and/or "primitive" features, such as rudimentary leaves (microphylls), ubiquitous dichotomous branching, heterospory, and the ligule. As the earliest diverging group of modern vascular plants, they are essential to understanding the evolution of plants as a whole.

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