Revision of the class Sorberacea (benthic tunicates) with descriptions of seven new species

Abstract

The benthic deep-sea class Sorberacea (Tunicata) is revised. All known species are redescribed and figured and seven new species are added. Diagnoses of the genera Sorbera, Gasterascidia, Oligotrema and Hexadactylus are given. The new generic name Hexadactylus replaces Hexacrobylm and a tabular key to the 12 species is provided. Hypotheses about the evolutionary processes in the Sorberacea are proposed and a comparison with Ascidiacea is given. The geographical distribution of sorberacean species and biogeographical affinities are discussed. The bathymetric distribution is particularly large since this class is characteristic of deep-sea bottoms.