 Rathbun synonymised "D. cristata" and "D. alluaudi" herself in 1906.The three species of "Deckenia" at that time were considered to be sufficiently distinct from other crabs to warrant placement in a separate subfamily (Deckeniinae) or family (Deckeniidae).In 1995, Peter K. L. Ng, Zdravko Števčić and Gerhard Pretzmann revised the family Deckeniidae, as then circumscribed, and concluded that ""D. alluaudi"" could not be accommodated with the other species of "Deckenia" in the same genus, or even in the same family.