Tethyan-relicts
Guides
Sessilia
acorn barnacles, sessile barnacles
Sessilia is an order of barnacles (Cirripedia) characterized by the absence of a stalk (peduncle), with the body attached directly to the substrate by a calcified base. The group comprises two orders: Verrucomorpha (two families) and Balanomorpha (14 families). Sessilia is considered monophyletic and likely derived from stalked ancestors. The Australasian region preserves the earliest stratigraphic records for several families including Pachylasmatidae, Tetraclitidae, Archaeobalanidae, and Verrucidae.