Puertoricomys (Proechimys) corozalus is the most enigmatic of the Puerto Rican rodents. It is an echimyid (Spiny Rat), known from a single specimen collected in 1930 from a "crevice in Corozal Limestone Quarry", a locality that has not been relocated. On the basis of its mineralized appearance, Puertoricomys has been considered "old" (mid-Pleistocene or older?) but this is very uncertain and even a Holocene age cannot be rejected. New specimens of this taxon would be of considerable interest in the interpretation of the Greater Antillean echimyid radiation.