We investigate mitochondrial (COI, 16S rDNA) and nuclear (ITS2, 28S rDNA) genetic structure of North East Atlantic lineages of Terebellides, a genus of sedentary annelids mainly inhabiting continental shelf and slope sediments. We demonstrate the presence of more than 25 species of which only seven are formally described. Species boundaries are determined with molecular data using a broad range of analytical methods. Many of the new species are common and wide spread, and the majority of the species are found in sympatry with several other species in the complex. Being one of the most regularly encountered annelid taxa in the North East Atlantic, it is more likely to find an undescribed species of Terebellides than a described one.

A phylogenetic analysis was conducted of the Nereidinae -those members of the Nereididae (Polychaeta) with pharyngeal paragnaths. We had two objectives: to test the monophyly of currently accepted genera, subgenera and informal subgeneric groupings within the Nereidinae, and, if warranted, to propose a more natural classification of the Nereidinae. Parsimony analyses were undertaken, including 52 terminal taxa from all genera and informal groupings from the large heterogeneous genera Nereis , Ceratonereis , Neanthes and Perinereis . Analyses of a character set of 52 informative characters yielded more than 10 000 equally parsimonious trees with a length of 176 steps (consistency index [CI] = 0.34, retention index [RI] = 0.66). Reweighting three times resulted in 445 most parsimonious trees with length 54.62 (CI = 0.59, RI = 0.79). Many characters widely used in nereidid systematics were found to exhibit high levels of homoplasy. The most parsimonious trees could not be rooted such that the selected ingroup, 'Nereididae with paragnaths', was monophyletic, causing us to reject the monophyly of the Nereidinae as currently defined. The following genera were well supported by the parsimony analyses and are newly diagnosed: Alitta , Ceratonereis , Pseudonereis , Simplisetia , Solomononereis and Unanereis . Alitta succinea , Pseudonereis cortezi , Pseudonereis noodti and Pseudonereis pseudonoodti are proposed as new combinations. The parsimony analysis supported the monophyly of neither Composetia , Neanthes , Nereis and Perinereis nor of any new groupings of remaining species presently placed in those genera. It is these poorly supported genera that comprise most species of Nereididae.

The Flabellinidae, a heterogeneous assembly of supposedly plesiomorphic to very derived sea slug groups, have not yet been addressed by integrative studies. Here novel material of rarely seen Arctic taxa as well as North Atlantic, North and South Pacific, and tropical Indo-West Pacific flabellinid species is investigated morpho-anatomically and with multi-locus markers (partial COI, 16S rDNA, 28S rDNA and H3) which were generated and analysed in a comprehensive aeolid taxon sampling. It was found that the current fam- RESEARCH ARTICLE Launched to accelerate biodiversity research A peer-reviewed open-access journalTatiana Korshunova et al. / ZooKeys 717: 1-139 (2017) 2 ily Flabellinidae is polyphyletic and its phylogeny and taxonomic patterns cannot be understood without considering members from all the Aeolidacean families and, based on a robust phylogenetic hypothesis, morpho-anatomical evolution of aeolids is more complex than suspected in earlier works and requires reclassification of the taxon. Morphological diversity of Flabellinidae is corroborated by molecular divergence rates and supports establishing three new families (Apataidae fam. n., Flabellinopsidae fam. n., Samlidae fam. n.), 16 new genera, 13 new species, and two new subspecies among the former Flabellinidae. Two families, namely Coryphellidae and Paracoryphellidae, are restored and traditional Flabellinidae is considerably restricted. The distinctness of the recently described family Unidentiidae is confirmed by both morphological and molecular data. Several species complexes among all ex-"Flabellinidae" lineages are recognised using both morphological and molecular data. The present study shows that Facelinidae and Aeolidiidae, together with traditional "Tergipedidae", deeply divide traditional "Flabellinidae." Diagnoses for all aeolidacean families are therefore provided and additionally two new non-flabellinid families (Abronicidae fam. n. and Murmaniidae fam. n.) within traditional tergipedids are established to accommodate molecular and morphological disparity. To address relationships and disparity, we propose a new family system for aeolids. Here the aeolidacean species are classified into at least 102 genera and 24 families. Operational rules for integration of morphological and molecular data for taxonomy are suggested.

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Macrobioerosion is a common process in marine ecosystems. Many types of rock-boring organisms break down hard substrates, particularly carbonate rocks and calcareous structures such as dead corals and shells. In paleontology, the presence of rocks with boreholes and fossil macroboring assemblage members is one of the primary diagnostic features of shallow marine paleo-environments. Here we describe a silicate rock-boring organism and an associated community in submerged siltstone rock outcrops in Kaladan River, Myanmar. The rock-boring mussel Lignopholas fluminalis is a close relative of the marine piddocks, and its borings belong to the ichnospecies Gastrochaenolites anauchen. The neotectonic uplift of the area leading to gradual decrease of the sea level with subsequent shift from estuarine to freshwater environment was the most likely driver for the origin of this community. Our findings highlight that rocks with macroborings are not an exclusive indicator of marine paleo-ecosystems, but may also reflect freshwater habitats.