In the skull, the rostrum (front part) is long and robust.
The nasal bones are short, not extending further back than the lacrimals, and the premaxillaries extend about as far back as the nasals.
The zygomatic notch, an extension at the front of the zygomatic plate, is present.
The plate's back margin is level with the front of the first upper molar.
A strong jugal bone is present in the zygomatic arch (cheekbone), so that the maxillary and squamosal bones, which form the front and back parts of the arch, respectively, do not overlap when seen from the side.
The narrowest part of the interorbital region (located between the eyes) is to the front and the region's margins exhibit strong beading.
Various crests develop on the rounded braincase, especially in old animals.
The parietal bones form part of the roof of the braincase and, unlike in some other rice rats, also extend to the sides of the braincase.
The interparietal bone at the back of the braincase is narrow and wedge-shaped, so that the parietal and occipital bones meet extensively.

The incisive foramina are very long, extending well between the molars.
The posterolateral palatal pits are well-developed and recessed into a fossa (depression).
The bony palate is relatively short, with the mesopterygoid fossa extending forward to the end of the molar row or even between the third molars.
The roof of the fossa is perforated by large sphenopalatine vacuities.
Usually, an alisphenoid strut is present; this extension of the alisphenoid bone separates two foramina (openings) in the skull, the masticatory–buccinator foramen and the foramen ovale accessorium.
The condition of various grooves and foramina of the skull indicates that the pattern of the arterial circulation of the head is derived.
The subsquamosal fenestra, an opening at the back of the skull determined by the shape of the squamosal bone, is large and the mastoid bone is perforated by a fenestra (opening).
The squamosal lacks a suspensory process that contacts the tegmen tympani, the roof of the tympanic cavity, a defining character of oryzomyines.

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.
In the skull, the rostrum (front part) is long and robust. The nasal bones are short, not extending further back than the lacrimals, and the premaxillaries extend about as far back as the nasals. The zygomatic notch, an extension at the front of the zygomatic plate, is present. The plate's back margin is level with the front of the first upper molar. A strong jugal bone is present in the zygomatic arch (cheekbone), so that the maxillary and squamosal bones, which form the front and back parts of the arch, respectively, do not overlap when seen from the side. The narrowest part of the interorbital region (located between the eyes) is to the front and the region's margins exhibit strong beading. Various crests develop on the rounded braincase, especially in old animals. The parietal bones form part of the roof of the braincase and, unlike in some other rice rats, also extend to the sides of the braincase. The interparietal bone at the back of the braincase is narrow and wedge-shaped, so that the parietal and occipital bones meet extensively.
The incisive foramina are very long, extending well between the molars. The posterolateral palatal pits are well-developed and recessed into a fossa (depression). The bony palate is relatively short, with the mesopterygoid fossa extending forward to the end of the molar row or even between the third molars. The roof of the fossa is perforated by large sphenopalatine vacuities. Usually, an alisphenoid strut is present; this extension of the alisphenoid bone separates two foramina (openings) in the skull, the masticatory–buccinator foramen and the foramen ovale accessorium. The condition of various grooves and foramina of the skull indicates that the pattern of the arterial circulation of the head is derived. The subsquamosal fenestra, an opening at the back of the skull determined by the shape of the squamosal bone, is large and the mastoid bone is perforated by a fenestra (opening). The squamosal lacks a suspensory process that contacts the tegmen tympani, the roof of the tympanic cavity, a defining character of oryzomyines.
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.
Eremoryzomys