A new abyssal hydrothermal verrucomorphan (Cirripedia; Sessilia): the most primitive living sessile barnacle

Abstract

A remarkable sessile barnacle, Neoverruca brachylepadoformis gen. et sp.nov., has been dicovered living near abyssal hydrothermal vents at 3600m in the Mariana Back-Arc Basin, Western Pacific. It has closer affinities with the earliest known sessile barnacles the Brachylepadomorpha (?Upper Jurassic-Miocene), than with any of the fossil or extant Balanomorpha (Upper Cretaceous-Holocene). Thus Neoverruca, the most primitive living sessile barnacle, is a "living fossil.' However, there are subtle characteristics of its shell that are diagnostic of the asymmetrical sessile barnacles, suborder Verrucomorpha (?Middle, Upper Cretaceous-Holocene). In having verrucomorphan specialization superimposed on the brachylepadomorphan plan, Neoverruca constitutes a "missing link' between these two suborders. As the sole surving member of an ancient radiation, Neoverruca adds significantly to our knowledge of the origin and evolution of sessile barnacles and the nature of their pedunculate ancestor. Furthermore, it heightens our appreciation of the role abyssal hydrothermal environments play in perpetuating ancient forms whose wide-ranging, predominantly shallow-water ancestors have long been extinct. -Authors