From the 1990s onwards, molecular phylogeny showed what botanists already suspected: dicotyledons are not a monophyletic group. They are a number of lineages, such as the magnoliids. Groups now known as basal angiosperms diverged earlier than the monocots did. The traditional dicots are a paraphyletic group. The largest clade of the dicotyledons are known as the eudicots. They are definitely monophyletic. They are distinguished from all other flowering plants by the structure of their pollen. Other dicotyledons and monocotyledons have an older type of pollen, whereas eudicots have derived pollen.