The “Fungia patella group” (Scleractinia, Fungiidae) revisited with a description of the mini mushroom coral Cycloseris boschmai sp. n.

Abstract. The recent taxonomic history of extant free-living Cycloseris species is briefly reviewed, resulting in the description of Cycloseris boschmai sp. n. (Scleractinia, Fungiidae) and a discussion on the validity of two other recently described species. Some Cycloseris species were previously considered to belong to the Fungia patella group, which also concerned misidentified museum specimens that actually belong to the new species. Other specimens of C. boschmai sp. n. were photographed and collected in the course of 30 years of fieldwork. The new mushroom coral is compared with other free-living Cycloseris species by means of an identification key. With a maximum diameter of 50 mm, it is the smallest free-living mushroom coral discovered so far. It can also be distinguished by its large primary order costae and variable colouration. Its distribution range is limited to the Coral Triangle, where it can be observed as an uncommon species on lower reef slopes.