Summary outline of current state of pyrgomatid systematics, as compiled from different taxonomic sources

Wall 4-plated or wholly concrescent; parietes solid or tubiferous; radii solid; basis calcareous, rarely tubiferous, membranous in Pyrgopsella (Newman and Ross 1976). The coral-dwelling barnacles.

Wall 4-plated or wholly concrescent; opercular valves normal or modified; when normal, tergum with weakly developed lateral depressor muscle crests, or crests lacking; when shell concrescent, sheath lacking paired sulci (Newman and Ross 1976).

TRIBE PYRGOMATINI (GRAY 1825)                 
Shell wholly calcareous; wall 4-plated or concrescent; outline or margin regular (when viewed from the top); orifice large; carinal ridge absent; walls interlock with calcareous basis; cirri and trophi normal; planktotrophic; lives in stony corals (Ross and Newman 1995).

Shell only partly calcareous; wall always concrescent and regular in outline; orifice large and lacking carinal ridge; basis wholly membranous; cirri and trophi normal and employed in planktotrophic feeding; lives in sponges (Ross and Newman 1995).

TRIBE HOEKIINI (ROSS AND NEWMAN 1995)                 
Shell calcareous; wall concrescent and irregular in outline (viewed from the top), orifice very small; carinal ridge present; inferior portion of basis calcareous while superior portion is membranous; lateral margin of wall in contact with tissue of host and not with basis; cirri aberrant; trophi modified for feeding on host tissue. Hoekiini are only found in the mussid coral Hydnophora and are parasitic. The coral host grows a pseudopolyp that covers the wall and aperture, upon which the barnacle feeds with modified trophi. The wall is suspended in coral tissue. The hypertrophied lateral margin is presumed site of metabolic activities between parasite & host (Ross and Newman 1995).

Four-plated wall; opercular valves not fused and normal; tergum w/ single large crest for lateral depressor muscle (Newman and Ross 1976). With a long, narrow, furrowed spur. Ceratoconchines share many characteristics with Cantellius euspinulosum including a 4-plated wall and a deep basis with broad ribs, buried deep in the host coral (Anderson 1992).

=Bosciinae (Newman and Ross 1976)
Wall wholly concrescent; opercular valves normal; tergum with feebly developed lateral depressor muscle crests, or crests lacking; sheath with paired sulci (Newman and Ross 1976). With a tergal spur like [pyrgomatines], but markedly divergent in their exserted occupancy of the coral host, fused wall, and modified cirri (Anderson 1992). "A re-examination of the operculum and associated structures of Megatrema anglicum has shown that the level of modification displayed in this species is intermediate between those of Armatobalanus arcuatus and Cantellius euspinulosum" (Anderson 1992).

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