Cephalodiscus

All known species live in a secreted coenecium attached to a rock substrate.^[3] Unlike Rhabdopleura, Cephalodiscus species do not form large colonies and are only pseudocolonial, but they do share a common area with individual buds for each zooid.^[3][4] Cephalodiscus zooids are also more mobile than their Rhabdopleura counterparts, and are able to move around within tubaria. Cephalodiscus zooids can be produced via asexual budding. There are a few pairs of tentacled arms, whereas Rhabdopleura has only one pair of arms.^[4]

19 living species of Cephalodiscus have been described:^[5]

• Cephalodiscus agglutinans Harmer & Ridewood, 1914
• Cephalodiscus atlanticus Bayer, 1962
• Cephalodiscus australiensis Johnston & Muirhead, 1951
• Cephalodiscus calciformis Emig, 1977
• Cephalodiscus densus Andersson 1907 [Cephalodiscus rarus Andersson, 1907; Cephalodiscus anderssoni Gravier 1912]
• Cephalodiscus dodecalophus McIntosh 1882
• Cephalodiscus evansi Ridewood
• Cephalodiscus fumosus John, 1932
• Cephalodiscus gilchristi Ridewood, 1908
• Cephalodiscus gracilis Harmer 1905
• Cephalodiscus graptolitoides Dilly 1993
• Cephalodiscus hodgsoni Ridewood, 1907 [Cephalodiscus aequatus Andersson 1907; Cephalodiscus inaequatus Andersson 1907]
• Cephalodiscus indicus Schepotieff 1909
• Cephalodiscus kempi John, 1932
• Cephalodiscus levinsoni Harmer 1905
• Cephalodiscus nigrescens Lankester 1905
• Cephalodiscus planitectus Miyamoto, Nishikawa and Namikawa, 2020
• Cephalodiscus sibogae Harmer 1905
• Cephalodiscus solidus Andersson, 1907

Extinct species include:

• †Cephalodiscus lutetianus Abrard, Dollfus & Soyer 1950
• †Cephalodiscus nusplingensis Schweigert & Dietl 2013

Proposed subgenera are Idiothecia, Demiothecia, Orthoecus, and Acoelothecia.^[3]