The jaw musculature of the phytosaur, machaeroprosopus

The phytosaur of the Triassic exhibits many interesting adaptive modifications of the diapsid skull. The modifications of the muscle attachment areas for the jaw muscles have been examined in comparison with the musculature of the recent forms Sphenodon and Alligator. It has been determined that the development of the fleshy anterior pterygoid and of the intramandibular muscles is an adaptation concomitant with the elongation of the snout. The modification of the temporal region in the phytosaur with the posterior extension of the squamosal is also seen to be an adaptation to gain speed in closing the great mouth. The forward position of the head‐neck joint would appear to gain advantage in the support of the heavy head. Such similarities as are seen between the phytosaur and the crocodilian may be accounted for as parallel adaptation.