According to the old tradition of zoological taxonomy, swamp deer originally were regarded as members of the genus Cervus. Rucervus was originally proposed by Hodgson Hodgson, B.H. 1838. Proceedings of Learned Societies. Linnaean Society, Feb. 20, 1838. Ann. Nat. Hist., 1, 152-154. as a subgenus of the genus Cervus. The original definition of Rucervus was mostly based on antler shape believed to be intermediate between that of 'elaphus' and 'hippelaphus'. Hodgson reported that upper canines are present only in males of barasingha, but the additional craniological material shows that upper canines are present in both sexes. Eld's deer was regarded as another species of the genus Rucervus, however, the recent genetic evidences suggest that Eld's deer is most closely related to Père David's deerPitraa, Fickela, Meijaard, Groves (2004). Evolution and phylogeny of old world deer. Molecular Phylogenetics and Evolution 33: 880–895. and should be placed in its own genus, Panolia.Groves (2006). The genus Cervus in eastern Eurasia. European Journal of Wildlife Research 52: 14–22Groves, C. and Grubb, P. 2011. Ungulate Taxonomy. The Johns Hopkins University Press, Baltimore, USA. However, it has recently been place back into Rucervus by the American Society of Mammalogists despite Eld's deer is not closely related to barasingha in genetics and antler structure.
