Lepidodendron — also known as scale tree — is an extinct genus of primitive, vascular, arborescent (tree-like) plant related to the lycopsids (club mosses). They were part of the coal forest flora. They sometimes reached heights of over 30 metres (100 ft), and the trunks were often over 1 m (3.3 ft) in diameter. They thrived during the Carboniferous Period (about 359.2 ± 2.5 Mya (million years ago) to about 299.0 ± 0.8 Mya) before going extinct. Sometimes erroneously called "giant club mosses", they were actually more closely related to today's quillworts than to modern club mosses.