From the Phascolomyidae, the two families, which may be collectively designated Phalangeroidea, differ by the circumstance that in the skull the tympanic process of the alisphenoid covers the tympanic cavity and reaches the paroccipital process.
The tympanic process of the alisphenoid bone of the skull is short, not covering the cavity of the tympanum, nor reaching the paroccipital process.
In the skull the lachrymal bone is large, the paroccipital process is directed vertically downwards and the tympanic bulla is hollow.
Behind this the exoccipital gives off a long paroccipital process.
The post-glenoid, post-tympanic and paroccipital processes of the skull are large, and there is an alisphenoid canal.