class Dicotyledones n : comprising seed plants that produce an embryo with paired cotyledons and net-veined leaves; divided into six (not always well distinguished) subclasses (or superorders): Magnoliidae and Hamamelidae (considered primitive); Caryophyllidae (an early and distinctive offshoot); and three more or less advanced groups: Dilleniidae; Rosidae; Asteridae [syn: {Dicotyledones}, {Dicotyledonae}, {class Dicotyledonae}, {Magnoliopsida}, {class Magnoliopsida}]