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. These lycopsids lack true leaves (having microphylls instead) and roots and thus represent an important node on the plant evolutionary tree. As the oldest extant division of the vascular plants, they are essential to understanding the evolution of plants as a whole.