Henri Rönkkö wrote:
I'm looking for detailed information on the structure of the theropod ear.According to a presentation at the !998 Paleontological Association meeting, the presence of the stapes, the same bone as the stirrup in our ears (though a completely different shape), goes at least as far back as _Ichthyostega_ in the Devonian. Its presence seems to indicate adaptation to hearing sound through the air as opposed to receiving sound under water.
Reptiles, including birds, have but this single bone, the stapes, connecting the eardrum to the inner ear, unlike we mammals, who have also incorporated two bones into our middle ears from the early amniote jaw. Consequently, dinosaurs have more bones in the jaw, but less bones in the ear when compared to mammals. In short, look at the ears of reptiles, including birds.
"Sue," the big _Tyrannosaurus rex_ specimen at the Field Museum in Chicago, has a preserved stapes. A cast of one of Sue's stapes is on view on the second floor of the museum, above Sue herself.
-- Ralph W. Miller III email@example.com