Figure 16.21   Transition to the mammals: (a) the Early Triassic cynodont Thrinaxodon; (b) the Early Jurassic mammal Megazostrodon; and (c, d) skulls of an early synapsid (c) and a mammal (d) to show the reduction in elements in the lower jaw and switch of the jaw joint. (a, based on Jenkins 1971; b, based on Jenkins & Parrington 1976; c, d, based on Gregory 1951/1957.)

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