The family Hamacanthidae (Demospongiae: Merliida) is reported from the abyssal plains for the first time, represented by two new species of Hamacantha (Vomerula) collected from the polymetallic nodule fields of the Clarion–Clipperton Zone (CCZ), Pacific Ocean. Hamacantha (V.) abyssalis sp. nov. is characterized by a single category of styles and diancistras, whilst lacking other microscleres such as sigmas, toxas, or raphides. Hamacantha (V.) apodiancistra sp. nov., likely the most abundant hamacanthid in the abyssal plains, is remarkable for the complete absence of diancistras—an apomorphy previously considered diagnostic of Hamacantha. Molecular phylogenetic analyses however confirmed its placement within Hamacantha, suggesting a secondary loss of this synapomorphy. The discovery of these species nearly doubles the known bathymetric range of Hamacantha to the abyssal zone and possibly highlights evolutionary trends toward reductions in body size, skeletal complexity, and spicule diversity in deep-sea demosponges.