Marine sponges that are able to erode calcareous substrates such as coral, mollusk shells, and limestone, also called boring or excavating sponges. Confirmed eroders belong to the families Samidae, Thoosidae, Clionaidae, Spirastrellidae, Acarnidae, and Phloeodictyidae, which are all demosponges. The best-known species belong to the genera Cliona, Pione, and Aka. Species are identified by their skeletal elements, morphology, tissue characteristics, and erosion traces.