A systematic revision of the North Eastern Atlantic shallow-water Haplosclerida (Porifera, Demospongiae), Part I: Introduction, Oceanapiidae and petrosiidae

The taxonomic history of the sponge order Haplosclerida is reviewed, with emphasis on literature concerning the Haplosclerida of the North Eastern Atlantic Ocean. The characters and their value for a phylogenetic classification are discussed. Two families are treated systematically: the Oceanapiidae, which have two representatives in the area, and the Petrosiidae, represented by one species. Emended diagnoses for the order, families, and genera are given.