gh there are no unusual adaptations in the known material, the animal possesses a combination of characteristics that distinguish it from all other known oryzomyines. The skull is known only from fragments. The nasal bones extend back to a point before or slightly behind the point where the maxillary, frontal, and lacrimal bones meet, and have a blunt back margin. The nasals extend slightly further back than the premaxillaries. The lacrimals articulate with both the frontals and the maxillaries, a trait that distinguishes Pennatomys from its closest relatives (which have lacrimals articulating mainly with the frontals). The interorbital region of the skull bears weak crests at its sides. The zygomatic plate, a bony plate at the side of the skull, is broad and its back margin is located in front of the first upper molar (M1). The incisive foramina, openings in the bony palate, extend back to a point next to the front root of M1. The palate itself is long and flat, extending beyond the third upper molars (M3). In the mandible (lower jaw), there is a capsular process – a protuberance at the back of the jawbone that houses the root of the lower incisor. Below the molars, the upper and lower masseteric ridges (crests which support some of the chewing muscles) are sometimes conjoined towards the front, and they extend forward to a point below the first lower molar (m1). The conjoined crests are one of the synapomorphic (shared-derived) characters of the Nectomys subclade. The maxillary toothrows are parallel to each o
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