The recognition of two externally distinct morphological forms of Finless Porpoises as separate biological species, the Indo-Pacific Finless Porpoise (Neophocaena phocaenoides) and the Narrow-ridged Finless Porpoise (N. asiaeorientalis), was accepted only recently when it was demonstrated that the two forms are reproductively isolated (and likely have been separated since the last glacial maximum) even though they occur sympatrically in a fairly large area of eastern Asia (Wang et al. 2008, Jefferson and Wang 2011). [Much of the literature published before ca 2010 refers to all Finless Porpoises (both species) as N. phocaenoides.] Differences in the external morphology of the dorsal aspect of the two species are distinguishable even amongst free-ranging animals (as opposed to only specimens in-hand) (Wang et al. 2010). Intermediates between the two main forms have never been reported even though several hundreds to thousands of carcasses have been examined. The two species also clearly differ in craniometry (Amano et al. 1992, Jefferson 2002). There is evidence to suggest subpopulation structure within Indo-Pacific Finless Porpoises in some areas (Jefferson 2002, Yang et al. 2008, Chen et al. 2010, Xu et al. 2010, Li et al. 2011, Ju et al. 2012, L. Li et al. 2013, S. Li et al. 2013, Jia et al. 2014, Lin et al. 2014) and this may apply throughout much of the species' distribution.