The most prevalent subgroup are the barnacles (subclass Cirripedia), constituting a little over 2,100 known species.[1]
The subgroup Facetotecta contains a single genus, Hansenocaris, known only from the tiny planktonic nauplii called "y-larvae". These larvae have no known adult form, though it is suspected that they are parasites, and their affinity is uncertain. Some researchers believe that they may be larval tantulocaridans. No larval tantulocaridans are currently known.[2]
The nauplius larvae (sometimes absent) can be both lecithotrophic (non-feeding) and planktotrophic (feeding), and is followed by a larval stage called the cyprid, which is always lecithotrophic. 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]
Classification
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. Previously, Thecostraca was considered a subclass of Maxillopoda.[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][6]
