Dynastidan \Dy*nas"ti*dan\, n. [Gr. ?, fem. of ?. See {Dynast}. The name alludes to the immense size of some species.] (Zool.) One of a group of gigantic, horned beetles, including {Dynastus Neptunus}, and the {Hercules beetle} ({Dynastus Hercules}) of tropical America, which grow to be six inches in length. [1913 Webster]