Pycnoclavella has occasionally been placed in a separate family, Pycnoclavellidae, although phylogenetic studies have recovered it as a relative of Clavelina. In multiple analyses, the monotypic genus Nephtheis appears to branch from within Clavelina.[5][6]
^Forbes, Edward; Hanley, Sylvanus (1853) [1848]. "Clavelinidæ; or, Social Ascidians". A History of British Mollusca, and Their Shells. Vol. I. Including the Tunicata, and the Families of Lamellibranchiata as far as Cyprinidæ. London: John van Voorst. pp. 25–28.
^ abShenkar, N., Gittenberger, A., Lambert, G., Rius, M., Moreira Da Rocha, R., Swalla, B.J., Turon, X. (2018). Shenkar N, Gittenberger A, Lambert G, Rius M, Moreira Da Rocha R, Swalla BJ, Turon X (eds.). "Clavelinidae Forbes & Hanley, 1848". Ascidiacea World Database. World Register of Marine Species. Retrieved February 26, 2024.