Posterolateral palatal pits

In anatomy, posterolateral palatal pits are gaps at the sides of the back of the bony palate, near the last molars. Posterolateral palatal pits are present, in various degrees of development, in several members of the rodent family Cricetidae. Many members of the family lack them or have only simple pits, but Arvicolinae (voles, lemmings, and relatives) and Oryzomyini (rice rats and relatives) have more highly developed posterolateral palatal pits. Posterolateral palatal pits are also present in some other rodents, including Glis, Jaculus, Hystrix, Abrocoma, Ctenomys, Chinchilla, and Lagidium.

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.

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