Link between reptiles and mammals.
Diarthrognathus possesses a jaw structure that is similar to both mammals and more basal synapsids. Its primitive jaw joint is located between the quadrate and articular bones, and its derived, mammalian jaw joint is located between the squamosal and dentary bones. It was the double jaw joint of Diarthrognathus that neatly bridges the reptiles and mammals, and thus rebuts a claim by creationists such as Duane Gish. The Synapsids, including Diarthrognathus, are Triassic and Jurassic ancestors of living mammals and had high metabolic rates. This meant consuming food (generally thought to be insects) in much greater quantity. To facilitate rapid digestion, these synapsids evolved mastication (chewing) and specialized teeth that aided chewing. Limbs also evolved to move under the body instead of to the side, allowing them to breathe more efficiently during locomotion. This helped make it possible to support their higher metabolic demands.