 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 . 
