 In the mandible , the mental foramen , an opening in the mandible just before the first molar , opens to the outside , not upwards as in a few other oryzomyines . The upper and lower masseteric ridges , which anchor some of the chewing muscles , usually join into a single crest at a point below the first molar and do not extend forward beyond the molar . There is no distinct capsular process of the lower incisor , a trait Eremoryzomys shares with only a few other oryzomyines . 
