RT Journal Article SR Electronic T1 Robust phylogenetic position of the enigmatic hydrozoan, Margelopsis haeckelii revealed within the family Corymorphidae JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.03.30.437375 DO 10.1101/2021.03.30.437375 A1 Daria Kupaeva A1 Tatiana Lebedeva A1 Tatiana Ashurkova A1 Andrey Prudkovsky A1 Daniel Vanwalleghem A1 Stanislav Kremnyov YR 2021 UL http://biorxiv.org/content/early/2021/03/31/2021.03.30.437375.abstract AB The life-cycle and polyp morphology of Margelopsidae representatives are very different from all other Aplanulata cnidarians. Until recently, their evolutionary origin and phylogenetic position has been a subject of significant speculation. A recent molecular study based only on COI data unexpectedly placed Margelopsidae as a sister group to all Aplanulata, despite the Margelopsid morphology suggests affiliation with Tubulariidae or Corymorphidae. Here we used multigene analyses, including nuclear (18S rRNA and 28S rRNA) and mitochondrial (16S rRNA and COI) markers of the Margelopsidae hydroid Margelopsis haeckelii Hartlaub, 1897, to resolve its phylogenetic position with respect to other hydrozoans. Our data provides strong evidence that M. haeckelii is a member of the family Corymorphydae, making the family Margelopsidae invalid. Furthermore, we show that medusa previously known as M. hartlaubii Browne, 1903 is sister to Plotocnide borealis, Wagner, 1885 and might be a member of Boreohydridae. The phylogenetic signal of polyp and medusa stages is discussed in light of concept of inconsistent evolution and molecular phylogenetic analysis.Competing Interest StatementThe authors have declared no competing interest.