Complex sentence: The diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth; but it is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, or a combination of factors.
Split into simpler sentences: The diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, or a combination of factors.