In this study we analyze the calcarean sponge diversity of the Adriatic Sea, the type locality of some of the first described species of calcarean sponges. Morphological and molecular approaches are combined for the taxonomic identification. Our results reveal six species new to science and provisionally endemic to the Adriatic Sea (Ascandra spalatensis sp. nov., Borojevia croatica sp. nov., Leucandra falakra sp. nov., L. spinifera sp. nov., Paraleucilla dalmatica sp. nov., and Sycon ancora sp. nov.), one species previously known only from the Southwestern Atlantic (Clathrina conifera), and three already known from the Adriatic Sea (Ascaltis reticulum, Borojevia cerebrum, and Clathrina primordialis). We confirm the presence of the alien species Paraleucilla magna in the Adriatic and again record Clathrina blanca, C. clathrus, and C. rubra. We emend the description of the genus Ascaltis, propose a lectotype for Borojevia cerebrum and synonymise B. decipiens with B. cerebrum. A checklist of all calcarean species previously and currently known from the Adriatic Sea (39 species) is given. The Central Adriatic is indicated as the richest calcarean sponge fauna sector; however, the biodiversity of this class is underestimated in the whole Adriatic Sea and new systematic surveys are desirable.
Porifera, Calcarea, Adriatic Sea, molecular taxonomy, morphological taxonomy.