4)AUTOSTYLIC This condition occurs when hyomandibular does not participate but becomes modified into columella or stapes of middle ear for transmitting sound waves.the upper jaw is completely fused by its processes to the bony skull and the lower jaw is suspended from the upper jaw.thus support from the hyomandibular is not needed,so it enters the middle ear as columella or stapes. Eg:bony fishes,tetrapoda.
12. Autostylic jaw suspension is divided into 3 subtypes a)HOLOSTYLIC In this upper jaw is firmly fused with skull and lower jaw suspended from it.hyoid arch is complete ,independent and not attached to skull; Eg:chimaeras b)MONIMOSTYLIC In many tetrapods , hyomandibular forms columella and articular articulates with quadrate. However ,the quadrate remains immovably attached with skull. c)STREPTOSTYLIC Quadrate is loosely attached and is movable at both ends a condition known as streptostylic.Eg:reptiles (lizzard,snakes)and birds