'' (skull, seen from below, with left posterolateral palatal pits indicated by a red circle) has the pits recessed into a fossa. Many members of the mainly South American cricetid subfamily
Sigmodontinae have posterolateral palatal pits. In
Oryzomyini (rice rats), the largest
tribe of the Sigmodontinae, all but some species—
Mindomys hammondi and
Sigmodontomys aphrastus usually have only one small pit on each side of the palate—have prominent posterolateral palatal pits, often more than one on each side of the palate. In many oryzomyines, the pits are located in a deep depression or
fossa. This depression has been termed the "palatal fossa" in the genus
Cerradomys; its varying depth serves as a diagnostic character separating some of the species. The presence of complex posterolateral palatal pits is a
synapomorphy either of Oryzomyini or of Oryzomyini minus
Mindomys. Members of the genus
Nephelomys usually have complex posterolateral palatal pits, recessed into deep fossae, but
N. caracolus and
N. nimbosus have simpler pits. One of the putative subdivisions within Oryzomyini,
Clade D, has posterolateral palatal pits recessed into a fossa as one of its synapomorphies, although the feature is reversed in several subgroups. The extinct island endemic
Noronhomys vespuccii also had smaller pits, perhaps because of its short palate. Among members of the tribe
Thomasomyini, posterolateral palatal pits are small or absent.
Aepeomys lacks them, but
Rhagomys longilingua does have posterolateral palatal pits. The possible thomasomyine
Abrawayaomys chebezi has small posterolateral palatal pits. Members of the
Phyllotini tribe always have posterolateral palatal pits. In some species, they are displaced to the back from their usual position just before the
mesopterygoid fossa into the fossa. The condition of the pits has been used to separate species of
Phyllotis. The tribe
Ichthyomyini is characterized by inconspicuous posterolateral palatal pits. ==Arvicolinae==