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| A side view of
skulls of early reptiles, mammal-like reptiles, and mammals
illustrating the differences in jaw and ear-bone structure. A) In
reptiles the jaw articulates between the quadrate and the articular.
In mammals the joint is formed between the squamosal and the dentary,
which is the only bone in the lower jaw. Note the transitional stage in mammal-like reptiles. B) Middle ear bones
of mammals developed from homologous bones in the reptilian jaw
joint. Image from Vaughan, et al. 2000; Copyright © 2000, Saunders College Publishing |
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