Skyggedelfin er først beskrevet af [[John Edward Gray]] i 1828, antageligvis på baggrund af et enkelt kranie og konserveret skind sendt fra [[Kap det Gode Håb]] til [[British Museum]] af en kaptajn Haviside.
TheSkyggedelfin duskyer dolphinmeget andnært the [[Pacific white-sided dolphin]] arebeslægtet consideredmed [[phylogeneticallyStillehavshvidside]] relatedog species.molekylærgenetiske Somedata researcherspeger havepå suggestedat thatde theyer areadskilt the same species but close scrutiny of morphological and life history parameters does not support this.<ref name= "Perrin"/> The two sister species diverged at aroundfor 1.9–3.0 millionmillioner yearsår agosiden.<ref name="Pmid">{{cite journal |last1=Cassens |first1=I |last2=Van Waerebeek |first2=K |last3=Best |first3=PB |last4=Tzika |first4=A |last5=Van Helden |first5=AL |last6=Crespo |first6=EA |last7=Milinkovitch |first7=MC |title=Evidence for male dispersal along the coasts but no migration in pelagic waters in dusky dolphins (''Lagenorhynchus obscurus''). |journal=Molecular ecology |volume=14 |issue=1 |pages=107–21 |year=2005 |pmid=15643955 |doi=10.1111/j.1365-294X.2004.02407.x}}</ref> Recent analysis of the mitochondrial cytochrome b gene indicates that the genus Lagenorhynchus, as traditionally conceived, is not a natural (monophyletic) group.<ref>LeDuc, R.G., Perrin, W.F., Dizon, A.E. (1999) "Phylogenetic relationships among the delphinid cetaceans based on full cytochrome b sequences", ''Marine Mammal Science'' 15(3):619–48.</ref> Another study finds that the dusky and the Pacific white-sided dolphin form the [[Sister_taxon#Cladograms|sister group]] to the (expanded) genus ''[[Cephalorhynchus]]''. If this placement is accurate, a new genus name will need to be coined to accommodate these two species.<ref>May-Collado, L., Agnarsson, I. (2006) "Cytochrome b and Bayesian inference of whale phylogeny", ''Molecular Phylogenetics and Evolution'' 38(2):344-54.</ref>
Dusky dolphins from Argentina and southwest Africa separated 2000 generations ago from an ancestral Atlantic population and since then diverged without much [[gene flow]].<ref name="Pmid" /> Most populations have low genetic diversity, with the Peruvian population being an expectation.<ref name= "Perrin"/> Possible hybrids of dusky dolphins have been described with a [[long-beaked common dolphin]]<ref>{{cite journal |last1=Reyes |first1=Julio C. |title=A Possible Case of Hybridism in Wild Dolphins |journal=Marine Mammal Science |volume=12 |pages=301–07 |year=1996 |doi=10.1111/j.1748-7692.1996.tb00581.x}}</ref> and a [[southern right whale dolphin]].<ref>{{cite journal |first1=Parissa |last1=Yazdi |year=2002 |url=http://www.aquaticmammalsjournal.org/share/AquaticMammalsIssueArchives/2002/AquaticMammals_28-02/28-02_Yazdi.pdf |title=A possible hybrid between the dusky dolphin (''Lagenorhynchus obscurus'') and the southern right whale dolphin (''Lissodelphis peronii'') |journal=Aquatic Mammals |volume=28 |pages=211–17}}</ref>
