Origin of the mammalian ear
Eventually the tooth-bearing dentary formed a new joint with the squamous portion of the temporal bone of the skull
One cynodont, Diarthrognathus, actually has a double jaw joint, with both articular-quadrojugal and dentary-squamosal joints
The articular and quadrojugal, now very small, were incorporated in the middle ear as sound-conducting bones, the malleus and incus. (They may have had this function all along; see pages 566-569)