Sometimes included in Lycopodiales

• Aquatic or marsh-growing fern allies
• Known to have existed since the Cenozoic

Wikipedia Word definitions in Wikipedia
Isoetales , formerly also written Isoëtales , is an order of plants in the class Isoetopsida . There are about 140-150 living species, all classified in the genus Isoetes (quillworts), with a cosmopolitan distribution but often scarce to rare. Living species ...