Genus Hymeniacidon Bowerbank, 1858

Hymeniacidon species are defined as Halichondriidae with encrusting or massively lobate shape and exclusively small styles (> 500 mm) for megascleres. Ectosomal tangential skeleton of intercrossing bundles and single megascleres. Choanosomal skeleton with ascending vague bundles and many loose, confusedly arranged megascleres (Erpenbeck & Van Soest 2002 [2004]). Fifty-four species are recognized worldwide (de Voogd, et al. 2023). The genus is cosmopolitan existing in all of the world’s oceans with the exception of the Bering, Black and Caspian seas; depth distribution is discontinuous from littoral to 440 m.