Lepidodendron is an extinct genus of primitive vascular plants belonging to order Lepidodendrales, part of a group of Lycopodiopsida known as scale trees or arborescent lycophytes, related to quillworts and lycopsids (club mosses). They were part of the coal forest flora. They sometimes reached heights of 50 metres (160 feet), and the trunks were often over 1 m (3.3 ft) in diameter. They thrived during the Carboniferous Period (358.9 to 298.9 million years ago). Sometimes erroneously called "giant club mosses", the genus was actually more closely related to modern quillworts than to modern club mosses. Within the form classification system used within paleobotany, Lepidodendron is both used for the whole plant as well as specifically the stems and leaves.