Quadrate and articular bones are much smaller and form part of the middle ear.
2.
In the Jurassic, their quadrate and articular bones evolved into the incus and malleus bones in the middle ear.
3.
On the dorsal surface of this region on the articular bone is a prominent ridge that is not seen in other archosauriforms.
4.
In addition, the lower jaw of the teleost is reduced to just three bones; the dentary, the angular bone and the articular bone.
5.
One theory is that in mammals, the articular bone has migrated to the middle ear to become the malleus, while the quadrate bone becomes the incus.
6.
The inner surface of the jaw is lined by a " prearticular " bone, while the articular bone forms the articulation with the skull proper.
7.
The malleus, or " hammer ", evolved from the articular bone of the lower jaw, and the incus, or " anvil ", from the quadrate.
8.
In forms transitional to mammals, the jaw joint is composed of a large, lower jaw bone ( similar to the dentary found in mammals ) that does not connect to the squamosal, but connects to the quadrate with a receding articular bone.
मोबाइल