The quadrate-articular jaw joint of reptiles also serve as reptilian auditory ossicles. Consequently, primitive amniotes like snakes hear by picking up vibrations from the ground with their jaw joints, that then transmit those signals to their middle ears. Mammals, instead of having the reptilian joint, possess a more robust dentary-squamosal jaw joint. In mammals, the articular-quadrate bones are bona fide components of the middle ear. We know this because these bones begin as cartilage in the lower jaw and skull during embryonic development and migrate to the middle ear to become the incus and stapes. Incidentally these bones are so reduced they are actually the smallest bones in mammals bodies Given that mammals and reptiles have completely separate jaw, and consequently, middle ear construction, what kind was probainognathus, given that its fossils show that it simultaneously possessed both types of jaw articulations?
Posted on: Wed, 24 Dec 2014 00:33:35 +0000
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