Description of a New Species of Rattus (Rodentia: Muridae) from East Borneo, Indonesia

We describe a new species of Rattus from Borneo that is distinguished from four other Bornean Rattus by the following characters: (1) body size smaller than R. baluensis, R. tiomanicus and R. argentiventer, but larger than R. exulans; (2) tail longer than head and body, distinguishing it from R. tiomanicus, R. argentiventer, and R. exulans, which have tail length equal to or slightly shorter than head and body length; but it shorter than R. baluensis (3) fresh specimens had creamy to yellowish ventral color; (4) compact, thick and heavy skull; (5) skull is much smaller than R. baluensis, R. tiomanicus and R. argentiventer, but larger than R. exulans; (6) wider and shorter nasal, and wider zygomatic arch than R. tiomanicus; (7) inter-orbital breadth slightly wider, braincase more rounded and inflated than R. tiomanicus; (8) tympanic bullae large relative to skull size; (9) incisive foramina wide relative to length, with posterior margins located just anterior to first molar; (10) mammae formula of female specimens has 4 pairs of teats (2 pectoral + 2 abdominal); and (11) palatal bridge is wide and constricting anteriorly.