A sciuromorphous zygomasseteric system is characterized by attachment of the lateral masseter muscle along the side of the rostrum.

Unlike hystricomorphous and myomorphous rodents, the medial masseter muscle does not pass through the infraorbital canal.

Some authorities would exclude the Geomyidae and Heteromyidae from that list due to the attachment of the medial masseter directly behind the zygomatic arch.

It has long been suggested that dormice (Gliridae) are not particularly related to the Myomorpha, and their zygomasseteric structure has been termed "pseudomyomorphy".

The connection between squirrels and dormice has been almost exclusively suggested through genetic studies, and to a lesser degree via the fossil rodent Reithroparamys.