A mandible and partial skeleton of Rhynchotherium falconeri is described from late Pliocene deposits of the 111 Ranch Locality in southeastern Arizona. The morphology of the mandible and m3 of the 111 Ranch individual is consistent with other specimens of Rhynchotherium and compares closely with previously reported R. falconeri from Arizona, as well as R. simpsoni from Florida. The 111 Ranch specimen is the basis for only the second description of postcranial material for the genus Rhynchotherium, and adds important morphological and ontogenetic attributes to this taxon. A morphometric analysis of specimens including the genotype indicates several junior synonyms are represented and the type specimen for the genus is no longer valid. A suggestion is made to raise F:AM 18225 to type status.