infrastapedial

from The Century Dictionary.

• Situated below the axis or main part of the stapes or columella auris: specifically applied to an element or part of that bone in some animals, as birds, supposed by Flower to represent the stylohyal bone of a mammal.
• noun An inferior element of the columella auris; an infrastapedial bone.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Anat.) Of or pertaining to a part of the columella of the ear, which in many animals projects below the connection with the stapes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective anatomy Of or pertaining to a part of the columella of the ear, which in many animals projects below the connection with the stapes.