肋木属是已灭绝的孢子树的一属，属于水韭纲肋木目。

它们是二叠纪-三叠纪灭绝事件中出现的最常见植物中的一种。

Pleuromeia is an extinct genus of spore plants assigned to the Isoetopsida. Pleuromeia dominated vegetations during the Early Triassic all over Eurasia and elsewhere. This suggests that it was an opportunistic pioneer plant that could grow on mineral soils and take advantage of a lack of competition. It may have slowly developed soils, making them more fit for recolonization with other plants that survived the Permian-Triassic extinction event in refugia, but this may also have been the result of improvement of climatic conditions. Conifers reoccurred in the Early Anisian, followed by the cycads and pteridosperms during the Late Anisian.