Until recently, two species were recognised in the genus Delphinus: the Short-beaked Common Dolphin (D. delphis) and the Long-beaked Common Dolphin (D. capensis), as described by Heyning and Perrin (1994). The morphological differences between D. delphis and D. capensis in the North Pacific (Heyning and Perrin 1994) were supported by molecular evidence from both mitochondrial and nuclear markers (Rosel et al. 1994). However, the genus exhibits a great deal of morphological variation globally and the criteria used to distinguish between the two species in the North Pacific appear not to apply elsewhere (Best 2007). In South Africa, Samaai et al. (2005) found that based on skull morphology the majority of specimens belonged to D. capensis, however two specimens were within the range for D. delphis from the North Pacific, and a third specimen fell between the ranges for D. delphis and D. capensis (Samaai et al. 2005). The same molecular markers that were used to differentiate the two sympatric species in the North Pacific failed to reveal any genetic distinction between the described morphotypes in South Africa (Best 2007). Subsequently, Cunha et al. (2015), in a global analysis of Delphinus which included nine specimens from the west coast of South Africa (eastern South Atlantic), concluded that all specimens analysed from the Atlantic Ocean belonged to D. delphis, and that D. capensis was not a genetically valid species. In 2016 the Society for Marine Mammalogy Committee on Taxonomy removed Delphinus capensis from its accepted list of marine mammal species and now recognises all Common Dolphins globally as belonging to a single species, Delphinus delphis (Committee on Taxonomy 2020). It recognises the following subspecies: <ul> <li>D. d. delphis Linnaeus, 1758. Common Dolphin</li> <li>D. d. bairdii Dall, 1873. Eastern North Pacific Long-beaked Common Dolphin</li> <li>D. d. ponticus Barabash, 1935. Black Sea Common Dolphin</li> <li>D. d. tropicalis van Bree, 1971. Indo-Pacific Common Dolphin</li> </ul> Cunha et al. (2015) noted that because the sympatric or parapatric Long-beaked and Short-beaked Common Dolphins off California in the eastern North Pacific appear not to interbreed, the Long-beaked Common Dolphins might eventually be described and recognised as a separate species, D. bairdii. Some researchers have considered the Long-beaked Common Dolphins in the Indo-Pacific, which has an exceptionally long beak, to constitute a separate species, D. tropicalis (Van Bree and Gallagher 1978; Rice 1998). However, another morphometric study concluded that that form should be considered a subspecies (Jefferson and Van Waerebeek 2002) and it is currently recognised as such, D. delphis tropicalis. The non-concordance of morphological and genetic data for Common Dolphins has caused much confusion and a rigorous global taxonomic study of the genus is needed. Further phylogenetic analyses are necessary to resolve the controversies surrounding the classification and nomenclature. More changes to Delphinus taxonomy should be expected.