Phoronids are a small type of exclusively marine invertebrate. They are distributed in most areas of the world ocean and often play an important role in marine communities as ecosystem engineers. However, the phylum consists of only 15 species, divided into two genera: Phoronis (11 species) and Phoronopsis (4 species). The identification of phoronids is usually very difficult due to the lack of distinctive morphological characteristics.

This contribution represents the first description of a deep-sea phoronid species. The material was collected in the Sea of ​​Okhotsk from seven locations (50°58.434'N 148°14.182'E; 50°58.566'N 148°14.271'E; 53°59.946'N 146°14.868'E; 54°00.207'N 146°18.581'E; 50°30.930'N 155°18.456'E; 50°30.928'N 155°18.444'E; and 50°30.956'N 155°18.489'E). Samples were acquired from depths of 786 to 1551 m using a bottom sampler and a remotely operated underwater vehicle. The morphology and anatomy of the specimens were studied using light microscopy, histological sections, and three-dimensional reconstructions of metanephridia. The obtained data were used for cladistic analysis.

Based on the obtained morphological and anatomical data and cladistic analysis, it was concluded that the discovered specimens belong to a new species of phoronids from the genus Phoronopsis. The studied species differ from other species of this genus in the number of longitudinal muscle bands and the number of tentacles in the lophophore. In addition, spermatoceigmata, clusters of spermatozoa, have been described for the first time in phoronids. It has been suggested that spermatoceigmata increase the probability of sperm delivery from one individual to another and, thus, are an adaptation to a deep sea lifestyle.