Protaeolidiella atra Baba, 1955 versus Pleurolidia juliae Burn, 1966: One or two species?

Abstract

Protaeolidiella atra Baba, 1955 and Pleurolidia juliae Burn, 1966 are two species traditionally regarded as the members of Aeolidiidae but recently attributed to Facelinidae. Because of their apparent similarities, Rudman (J Molluscan Stud 56:505–514, 1990) rendered P. juliae as a junior synonym of P. atra. In this paper, we conducted a review of both species and completed their descriptions with new data regarding the anatomy of the reproductive system. P. atra and P. juliae have differences in their colouration, number of cerata and characteristics of their reproductive system. Based on these differences, we conclude that these species are not conspecific and should be regarded as distinct taxa.