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A natural whale fall was opportunistically trawled at ~1000 m depth during the 2017 research vessel ‘Investigator’ voyage whilst sampling bathyal and abyssal communities along the eastern Australian margin. Colonising the whale bones were a diverse assemblage of annelids including three new species of free-living Phyllodocida (Boudemos paulinae sp. nov, Pleijelius keni sp. nov. and Microphthalmus hvalr sp. nov.). Boudemos paulinae sp. nov. (Chrysopetalidae, Calamyzinae) is a smaller sized species (< 2 mm) compared to its congeners (35-40 mm) and exhibits stylet jaw and notochaetal morphology observed in juveniles of the sister species Boudemos flokati (Dahlgren, Glover, Baco & Smith, 2004) from whale falls in the NE Pacific. Notochaetal serration patterns distinguish Pleijelius keni sp. nov. from its only congener P. longae Salazar-Vallejo & Orensanz, 2006 described in the family Hesionidae from wood falls in NW Atlantic. DNA sequence analysis using the COI, 16S and 18S gene fragments revealed Pleijelius keni sp. nov. fell within the Microphthalmidae clade, this relationship was also supported by morphological observations. These results necessitated a formal transfer of the genus Pleijelius to the family Microphthalmidae. Microphthalmus hvalr sp. nov. is the first Microphthalmus species described from bathyal depths and is distinguished from its numerous congeners inhabiting shallow-water interstitial sediments by the absence of notochaetae.

Pilargidae is a family of free-living and burrowing marine annelids. A lack of available molecular data for most of these species has precluded a molecular assessment of their phylogenetic relationships and has left uncertain the placement of Antonbruunia, which is hypothesized to be either a member of Pilargidae or its sister clade, the monotypic family Antonbruunidae. In this study, we describe the new species Antonbruunia milenae sp. nov., found at 845 m of depth off the coast of San Diego, California, USA, and we address the phylogeny of these organisms using 15 novel mitogenomes and multiple Sanger-sequenced loci. Our results show that Antonbruunia falls within Pilargidae, making Antonbruunidae a junior synonym of Pilargidae. Glyphohesione was transferred from Pilarginae to Synelminae, the previously unassigned genera Otopsis and Antonbruunia were shown to belong within Synelminae, and Hermundura was assigned to Phyllodocida incertae sedis. Sigambra was found to be non-monophyletic. Four different mitogenome gene orders were found among Pilargidae. Changes between the gene orders and the ancestral state gene order of the family were inferred. Two species have introns within the COI gene. These efforts represent a significant expansion of the available molecular resources for pilargids, as well as the basis for a more stable taxonomy. [ABSTRACT FROM AUTHOR]

Pilargidae is a family of free-living and burrowing marine annelids. A lack of available molecular data for most of these species has precluded a molecular assessment of their phylogenetic relationships and has left uncertain the placement of Antonbruunia, which is hypothesized to be either a member of Pilargidae or its sister clade, the monotypic family Antonbruunidae. In this study, we describe the new species Antonbruunia milenae sp. nov., found at 845 m of depth off the coast of San Diego, California, USA, and we address the phylogeny of these organisms using 15 novel mitogenomes and multiple Sanger-sequenced loci. Our results show that Antonbruunia falls within Pilargidae, making Antonbruunidae a junior synonym of Pilargidae. Glyphohesione was transferred from Pilarginae to Synelminae, the previously unassigned genera Otopsis and Antonbruunia were shown to belong within Synelminae, and Hermundura was assigned to Phyllodocida incertae sedis. Sigambra was found to be non-monophyletic. Four different mitogenome gene orders were found among Pilargidae. Changes between the gene orders and the ancestral state gene order of the family were inferred. Two species have introns within the COI gene. These efforts represent a significant expansion of the available molecular resources for pilargids, as well as the basis for a more stable taxonomy.