ACROTHORACICA, GRUVEL, 1905

Chan, Benny K. K., Dreyer, Niklas, Gale, Andy S., Glenner, Henrik, Ewers-Saucedo, Christine, Pérez-Losada, Marcos, Kolbasov, Gregory A., Crandall, Keith A. & Høeg, Jens T., 2021, The evolutionary diversity of barnacles, with an updated classification of fossil and living forms, Zoological Journal of the Linnean Society 193, pp. 789-846 : 824

INFRACLASS ACROTHORACICA, GRUVEL, 1905

Diagnosis: Monophyletic by molecular analyses. Minute, burrowing females found primarily in calcareous substrates (corals, molluscs, barnacle shells, bryozoans etc.), with soft carapace, accompanied by dwarf males. All female and male calcareous shell plates are a single pair of largely chitinous plates (opercular bars) guarding the aperture, three to five pairs of terminal cirri, gathering in the posterior elongated portion of the thorax, single pair of developed or reduced cirri located at the side of the mouth, caudal appendages present or absent, abdomen reduced in adults. Borings probably made by acrothoracicans are known as far back as the Lower Devonian, but do not provide morphological information; these are trace fossils and have no taxonomic validity.