Insular Mid-Pleistocene Giant Rats from the So’a Basin (Flores, Indonesia)

Excavations undertaken at Mata Menge, the securely dated Middle Pleistocene open site on the Indonesian island of Flores, have resulted in the recovery of over 670 well-preserved fossil murine molars from two distinct stratigraphic intervals. This research is the first systematic metric and morphological analysis of this material, with the results indicating the predominance of a single murine species, though the finds from the lower interval (0.7 million years ago) are for the most part significantly smaller than those recovered from the ~70,000-year-younger upper interval. Comparison of our findings with the analyses of the Flores endemic recent and fossil giant rats undertaken by Hooijer in 1957 and Musser in 1981 indicates the Mata Menge large murine maxillary molars, and, in particular, those from the lower interval are very similar to the limited Middle Pleistocene material Musser designated to be Hooijeromys nusatenggara. However, the associated Mata Menge mandibular molars are most similar to, though smaller than, the mid-Holocene Papagomys theodorverhoeveni. In addition to providing a detailed reference for future studies of large fossil murines excavated from Wallacea, our findings indicate Musser’s reassignment of Hooijer’s maxillary holotype of P. verhoeveni to P. armandvillei would benefit from re-examination.