Phylogenetic position of Xenoleberis Kornicker, 1994 within Cylindroleberidinae (Ostracoda: Myodocopa) with descriptions of three new species and one new genus from the Northwestern Pacific Ocean

Cylindroleberididae is a peculiar ostracod myodocopid family, characterized by the presence of gills. It accounts for over 200 species described from all bathymetric ranges and from all the world’s oceans. Nevertheless, its biodiversity is still underestimated, with each study brining new taxa to the list. As a result of recent sampling effort in seas around Korea and Japan, we report five cylindroleberid taxa. One of those is described as a new genus (Toyoshioleberis gen. nov.), and four belong to Xenoleberis Kornicker, 1994. Of the latter, three are described as new species, and one has already been reported from Japan, but is the first record for Korea. In fact, our study is also the first record of the family from this country. Having fresh samples provided an opportunity to obtain sequences of three gene markers (16S, 28S, and 18S rRNA), and, by combining those with the ones belonging to Cylindroleberididae available in GenBank, we reconstruct a molecular phylogeny with the aim to assess the position of the new taxa within the family and try to resolve the currently polyphyletic nature of some cylindroleberid taxa. The results of the phylogenetic analyses indicate the monophyly of Xenoleberis and its deep separation from Toyoshioleberis, along with distinct morphological features genetics to support our taxonomic decision. In addition, the phylogenetic results confirm that the general systematic of Cylindroleberididae should be reassessed, in particular the tribes of the subfamily Cyclasteropinae should be given a higher systematic ranking, as suggested previously based on morphology alone.