Balanoid barnacles from the Miocene of the Alaska Peninsula, and their relevance to the extant boreal barnacle fauna

Abstract

The barnacle fauna of the Miocene Bear Lake Formation of the Alaska Peninsula includes Chirona (Chirona) alaskana n. sp., and three species of Balanus Da Costa conspecific with or related to the extant species Balanus balanus (Linnaeus), B. nubilus Darwin, and B. crenatus (Bruguière). Although the Bear Lake fauna lived in warm temperate waters, its modern counterparts are found primarily in boreo-arctic and cool temperate regions of the North Pacific and North Atlantic Oceans. Miocene barnacle faunas in Japan are similar to those of the Alaska Peninsula, lacking relatives of B. nubilus, but including Semibalanus Pilsbry, which does not appear until the Pleistocene in the eastern Pacific. Elements of this boreo-Arctic fauna do not appear in the North Atlantic basin until the Pleistocene, suggesting migration of the fauna into the Atlantic with the opening of the Bering Straits.