title: Ringiculid bubble snails recovered as the sister group to sea slugs (Nudipleura).
abstract: Euthyneuran gastropods represent one of the most diverse lineages in Mollusca (with over 30,000 species), play significant ecological roles in aquatic and terrestrial environments and affect many aspects of human life. However, our understanding of their evolutionary relationships remains incomplete due to missing data for key phylogenetic lineages. The present study integrates such a neglected, ancient snail family Ringiculidae into a molecular systematics of Euthyneura for the first time, and is supplemented by the first microanatomical data. Surprisingly, both molecular and morphological features present compelling evidence for the common ancestry of ringiculid snails with the highly dissimilar Nudipleura-the most species-rich and well-known taxon of sea slugs (nudibranchs and pleurobranchoids). A new taxon name Ringipleura is proposed here for these long-lost sisters, as one of three major euthyneuran clades with late Palaeozoic origins, along with Acteonacea (Acteonoidea + Rissoelloidea) and Tectipleura (Euopisthobranchia + Panpulmonata). The early Euthyneura are suggested to be at least temporary burrowers with a characteristic 'bubble' shell, hypertrophied foot and headshield as exemplified by many extant subtaxa with an infaunal mode of life, while the expansion of the mantle might have triggered the explosive Mesozoic radiation of the clade into diverse ecological niches.
authors: Department of Marine Ecosystems Dynamics, Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8564, Japan.
authors: Yasunori
authors: Y
authors: Kano
authors: SNSB-Bavarian State Collection of Zoology, Münchhausenstr. 21, 81247 München, Germany.|Department Biology II, BioZentrum, Ludwig-Maximilians-Universität, Großhadernerstr. 2, 82152 Planegg-Martinsried, Germany.
authors: Bastian
authors: B
authors: Brenzinger
authors: SNSB-Bavarian State Collection of Paleontology and Geology, Geobio Center LMU, Richard-Wagner-Str. 10, 80333 München, Germany.
authors: Alexander
authors: A
authors: Nützel
authors: Western Australian Museum, Locked Bag 49, Welshpool DC, Perth, WA 6986, Australia.
authors: Nerida G
authors: NG
authors: Wilson
authors: SNSB-Bavarian State Collection of Zoology, Münchhausenstr. 21, 81247 München, Germany.|Department Biology II, BioZentrum, Ludwig-Maximilians-Universität, Großhadernerstr. 2, 82152 Planegg-Martinsried, Germany.
authors: Michael
authors: M
authors: Schrödl
mesh_terms: D000818:Animals; D001483:Base Sequence; D004247:DNA / Q000302:isolation & purification / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000235:genetics; D049851:Gastropoda / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics; D016013:Likelihood Functions; D010802:Phylogeny; D012337:RNA, Ribosomal, 18S / Q000737:chemistry / Q000235:genetics; D012339:RNA, Ribosomal, 28S / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D012908:Snails / Q000033:anatomy & histology / Q000145:classification* / Q000235:genetics
chemical_list: D012337:RNA, Ribosomal, 18S; D012339:RNA, Ribosomal, 28S; D004247:DNA; D003576:Electron Transport Complex IV