Origin and phylogeny of verrucomorph barnacles (Crustacea, Cirripedia, Thoracica)

<div><p>Asymmetrical thoracican cirripedes of superfically similar ‘verrucomorph’ morphology are shown to have evolved independently three times from pedunculate ancestors. In each case, the loss of a peduncle was accompanied by preferential attachment on one side or the other, such that the rostrum, carina and one of each paired scuta and terga (fixed) formed a wall-like structure; the opposite scutum and tergum (free or moveable) transforming into an opercular lid closed by the scutal adductor muscle. True verrucomorphs (<i>Eoverruca</i> + Verrucidae) have their origin in the mid-Cretaceous sessile genera <i>Pycnolepas</i> and <i>Faxelepas</i> gen. nov., which demonstrate a marked, but facultative, tendency towards capitular asymmetry, confirmed by strong morphological similarities in plate morphology to the basal verrucomorph genus <i>Eoverruca</i> of Late Cretaceous age. <i>Proverruca</i>, another Late Cretaceous asymmetrical form, is not closely related; it evolved independently from a scalpelliform ancestor. The extant hydrothermal vent genera <i>Neoverruca</i> and <i>Imbricaverruca</i> evolved from symmetrical scalpelliforms of the family Neolepadidae, as demonstrated by both molecular and morphological evidence. Cladistic analysis of 38 characters in 14 living and fossil taxa has yielded a consensus tree showing a monophyletic Verrucomorpha, made up of a stem group (<i>Eoverruca</i>) and crown group (Verrucidae). <i>Faxelepas bruennichi</i> comb. nov. and <i>Pycnolepas rigida</i> are sister taxa to the Verrucomorpha, and evolved from a pedunculate ancestor. The Verrucidae are divided into a basal stem group (<i>Altiverruca</i>, <i>Globosoverruca</i>) and a derived crown group (all other genera). Within the crown group, the monophyletic Priscoverrucinae subfam. nov. is identified. Systematic revision of Cretaceous verrucomorphs and basal sessilians includes description of <i>Pedupycnolepas</i> gen. nov., <i>Faxelepas</i> gen. nov., <i>Youngiverruca</i> gen. nov. and <i>Priscoverruca</i> gen. nov. and two new species, <i>Youngiverruca ruegenensis</i> sp. nov. and <i>Verruca jagti</i> sp. nov. The development of asymmetry was perhaps a feeding adaptation, enabling barnacles to catch crawling benthic prey in deep ocean environments where food is scarce.</p><p>http://zoobank.org/urn:lsid:zoobank.org:pub:738C0B07-159F-41C9-8E93-ACE8A0BE85E8</p>