The specific name minor was first used by Herbst (1782); he used it with respect to a wide range of previously published reports (containing multiple species by today's nomenclature), but also apparently to a single on-hand specimen. Although that specimen is now lost, Shih et al. (2021) make a strong argument that the specimen represented what today is Austruca annulipes. Because the name minor went unused for so long, zoological nomenclature allows for the reverseal of priority and Cancer vocans minor is now considered a “nomen oblitum,” rather than having priority over Gelasimus annulipes H. Milne Edwards, 1837.
The name minor was later independently used as Gelasimus minor Owen, 1839, to describe a species from Hawaii. No fiddler crabs are found on Hawaii, but a variety of details point to this being collected further west and likely representing Austruca perplexa (Milne Edwards, 1852). Since Gelasimus minor Owen, 1839, is a clear junior homonym of Cancer vocans minor, it was unavailble to Owen and does not take precedence over Austruca perplexa.