 The species <unk> were collected from San Diego Bay , California . The specific epithet dipterura is derived from the Latin di ( " two " ) , <unk> ( " wing " ) , and <unk> ( " tail " ) , referring to the fin folds on both sides of its tail . Rat @-@ tailed stingray is a former common name for this species . Lisa <unk> 's 2001 phylogenetic analysis , based on morphology , determined the diamond stingray and the <unk> stingray ( D. say ) of the western Atlantic Ocean to be sister species , that likely diverged before or with the formation of the Isthmus of Panama ( c . 3 Ma ) . In addition , the two were found to be the second @-@ most basal taxa in their genus , after the common stingray ( D. <unk> ) . 
