Balanus

Balanus is a genus of barnacles in the family Balanidae of the subphylum Crustacea. This genus is known in the fossil record from the Jurassic to the Quaternary periods (age range: from 189.6 to 0.0 million years ago.). Fossil shells within this genus have been found all over the world. The bodies of these organisms are totally enclosed by a stony gray-whitish shell. The size of these shells ranges from 5 millimeters to 10 centimeters. They take the form of a cone consisting of six plates fixed on the rocks. The active animal can only be observed within the water when the shell opens and the barnacles expose two branched appendages (cirri ) regularly hitting the water to catch food. They mainly feed on plankton. These barnacles can be found in coastal areas at low shallow depth, although they can also be seen living out of the water. They commonly colonize stones, rocks and shells. They are found in abundance on the shells of mussels. Species within the genus Balanus include: The species Balanus balanoides (common barnacle, common rock barnacle, northern rock barnacle) has been reclassified as Semibalanus balanoides in the family Archaeobalanidae, due to its membranous base.