Indonesian sponges of the genus Petrosia Vosmaer (Demospongiae: Haplosclerida)

Sponges of the genus Petrosia (Demospongiae: Haplosclerida) are large and characteristic components of many Indonesian reefs. We identify and provide descriptions of seven species of Petrosia collected recently on SW Sulawesi reefs (Eastern Indonesia), two of which are new to science: Petrosia (Petrosia) alfiani spec. nov. and Petrosia (Petrosia) hoeksemai spec. nov. Additional species recorded are Petrosia (Petrosia) lignosa Wilson, 1925, Petrosia (Petrosia) nigricans Lindgren, 1897, Petrosia (Petrosia) plana Wilson, 1925, Petrosia (Strongylophora) corticata (Wilson, 1925) and Petrosia (Strongylophora) strongylata Thiele, 1903. The species are discussed and compared with Petrosia records from other Indonesian and neighbouring Indo-West Pacific areas. We also present a key to the common Petrosia species of Sulawesi.