Composition of the subclass has also varied; however, by definition it always includes the family Asteraceae (Compositae).
In the modern APG IV system of classification, asterid and euasterid are names for clades with a composition similar to that of Asteridae.
To a large extent Cronquist's subclass Asteridae corresponds with the older concepts of Sympetalae and Tubiflorae, groups that were defined by having their petals united into a tube.
However, these older classifications contained some sympetalous families, such as Cucurbitaceae, that are now known not to be closely related.
Recent phylogenetic studies have suggested that several families, including three major orders not included in Asteridae by Cronquist, Ericales, Cornales, and Apiales, also belong to the asterid group.