Butterfly Ray Gymnura bimaculata, a Junior Synonym of G.japonica

Abstract

Gymnura japonica (Temminck et Schlegel, 1850) was described on the basis of specimens collected at Nagasaki.In the mean time G. bimaculata (Norman, 1925) was described on a specimen, 257 mm in total length, collected in the Chinese coast.In his brief description (18 lines) Norman pointed out characteristics of his new species as“it's tail is a little longer in comparison with known butterfly rays and there is a pair of oval bluish white ocelli at posterior side of spiracle.”Norman's species has long been regarded as valid by subsequent workers.Among them, some have either a pair of large white ocelli on disc or only one ocellus, or have a pair of large and small ocelli.Variation in pattern of white ocelli and in morphometric characters were studied on 24 individuals (specimens of Mus.Tokyo Univ. Fish., MTUF 22083-22106) from the East China Sea including young specimens.There is no valid reason for separation of two nominal species, and G.bimaculata should be regarded as a junior synonym of G.japonica.