Nowadays, rice rats (Oryzomyini tribe) have a large taxonomic diversity on the American continent. Yet, they used to be present in the Lesser Antilles before their disappearance following the European colonisation. These extinct insular representatives have been the subject of numerous studies including genetic and morphometric, and anatomical descriptions aiming to understand their past diversity. Three genera specific to this area are now known that could be associated with a geographically structured phenotypic diversity. In our study, the combined analysis of morphometric signals (sizes and shapes) from the teeth and mandibles of 215 specimens from 33 archaeological sites on 11 islands, highlights the presence of an even larger diversity composed by 6 morphotypes and 11 sub-morphotypes. These groups, which subdivide the three previous clusters, help to clarify the archaeobiogeography of oryzomyine in the Lesser Antilles. These morphotypic differences, which respect a geographical organisation, favour the hypothesis of differentiation induced by population isolation within islands. However, the coexistence of several sub-morphotypes on some of the islands may reveal ecological differenciation. All together our data revealed a greater diversity than known before for an extinct group of rice rats in the Lesser Antilles archipelago only allowed by a bioarchaeological study combining multiple lines of evidence.