obsolete zygomasseteric system true obsoleted as it did not represent a structure The zygomasseteric system (or zygomasseteric structure) in rodents is the anatomical arrangement of the masseter muscle of the jaw and the zygomatic arch of the skull. The anteroposterior or propalinal (front-to-back) motion of the rodent jaw is enabled by an extension of the zygomatic arch and the division of the masseter into three distinct parts. The main types are described as protrogomorphous, sciuromorphous, hystricomorphous, and myomorphous. UBERON:0013466