Gymnodoris pattani, a new dorid nudibranch from Pattani Bay, Gulf of Thailand (Gastropoda, Nudibranchia)

Several specimens of a new dorid nudibranch have been found in Yaring River, Pattani Province in southern Thailand. The species clearly belongs to the genus Gymnodoris, and is described and named G. pattani. It can be distinguished from all other species described in the genus by its translucently greenish colour, lack of notable colour markings, smooth skin, low number of about 3 lamellae on the rhinophores, a circlet of about 20 simple gill leaflets, its broad foot, and its brackish water habitat.