Ossicles
Studies have shown that ear bones in mammal embryos are attached to the dentary, which is part of the lower jaw. These are ossified (turned into bone) portions of cartilage -- called Meckel's cartilage -- that are attached to the jaw. As the embryo develops, the cartilage hardens to form bone.  Later in development, the bone structure breaks loose from the jaw and migrates to the inner ear area.  The structure is known as the middle ear, and is made up of the incus, stapes, malleus, and tympanic membrane.  These correspond to the quadrate, prearticular, articular, and angular structures in earlier land vertebrates.