[1] The subgroup Facetotecta contains a single genus, Hansenocaris, known only from the tiny planktonic nauplii called "y-larvae".

The cypridoid larvae are referred to as the y-cyprid in the Facetotecta, the a-cyprid in the Ascothoracida, and the c-cyprid, or just cyprid, in the Cirripedia.

[4][5] This article follows Chan et al. (2021) and the World Register of Marine Species in placing Thecostraca as a class of Crustacea and in the following classification of thecostracans down to the level of orders.

[2] Significant changes in the organization of Cirripedia's orders, families, and genera were introduced in 2021 by Chan et al. and accepted by the World Register of Marine Species.

[1][7] Facetotecta Laurida Dendrogastrida Cryptophialida Lithoglyptida Iblomorpha Eolepadomorpha† Archaeolepadomorpha † Pollicipedomorpha Calanticomorpha Scalpellomorpha Brachylepadomorpha† Verrucomorpha Balanomorpha Rhizocephala