 The blue stingray ( Dasyatis <unk> ) of southern Africa has long been regarded as a variant of the common stingray . However , the common stingray lacks the blue markings of the other species and differs in morphological and <unk> characters , which led the latter to be definitively recognized as a separate species by Paul Cowley and Leonard Compagno in 1993 . The distinction between this species and the similar Tortonese 's stingray ( D. <unk> ) of the Mediterranean is poorly understood and may not be valid , requiring further investigation . 
