PLEUROMEIA

a genus of extinct club mosses, order Pleuromeiales (class Lycopsida). It represents a curious line of small, treelike Late Triassic Period (from 230 to 208 million years ago) lycopsids, perhaps related to members of the present-day quillwort genus (Isoetes). Pleuromeia's unbranched trunk grew to more than 1 m (40 inches) in height and about 10 cm (4 inches) in diameter; it bore a zone of elongated leaves near its tip, at which one large terminal cone was produced. Its rootlets were spirally arranged on four or more lobes that flared out at the base of the trunk, inviting comparisons with several other treelike lycopsids (e.g., Lepidodendron, Sigillaria).