Two species of freshwater dolphin are known to have existed in the Yangtse River, China, for over two thousand years. One is a white form, the Baiji (Lipotes vexllifer), the other is black and called the river pig (iiang zhu) or black finless porpoise (Neophocaena phocaenoides). PILLERI and GIHR (1972), on the basis of certain features, have divided the genus Neophocaena into three species: N. phocaenoides with a distribution in warmer waters, N. sunameri from colder Japanese waters and N. asiaeorientalis from the Yangtse river and its estuary. VAN BREE (1973) has, however, criticized the significance of the alleged differences and considers that the single species N. phocaenoides occurs in all warmer waters along coasts of southern end eastern Asia with a ”ribbon-like” distribution. PILLERI and GIHR (1975) have subsequently given details of body and skull measurements of the three species to support their claims. PILLERI and CHEN PEI-XUN (1979) have described differences in the disposition of the small tubercles on the dorsal region of the body which distinguish N. phocaenoides from N. asiaeorientalis.
Nothing is known about the reproductive organs of the Yangtse finless porpoise, CHEN et al. (1979) considered that birth occurred between February and April and that from mid April until May calves are carried on the mothers’ backs. The scanty information on reproduction in N. phocaenoides from warmer waters has been reviewed by HARRISON and MCBREARTY (1973-74). These authors described the appearances of the gonads from three males (130-150 cm) and three females (98-155 cm), none of which was pregnant.