Balanidae (acorn barnacles; order Thoracica, suborder Balanomorpha) Family of radially symmetrical, balanomorph (sessile symmetrical) barnacles, including the familiar barnacles of the genus Balanus exposed at low tide and characteristic of the littoral zone. Balanus has a fossil record extending back to the Eocene.

Balanidae (acorn barnacles; order Thoracica, suborder Balanomorpha) Family of radially symmetrical, balanomorph barnacles in which the third pair of cerci resemble the second rather than the fourth, and in which there are no caudal appendages. The family includes the familiar barnacles exposed at low tide, of the genus Balanus, which has been divided into 10 subgenera.