156 MAURICE G. MEHL 



phytosaurs. The seemingly common goal in the modifications 

 of all the phytosaurs suggests similar habits. Of the probable 

 habits of Machaeroprosopus the writer has stated in another 

 place •} 



All of the phytosaurs were supposedly more or less amphibious in habit. 

 StUl, the heavy dermal armor of several of the forms would indicate that a 

 very considerable part of their time was spent on the land. The posterior 

 position of the nares is usually not considered a distinct aquatic adaptation 

 in the case of the phytosaurs. It is rather explained, along with the long 

 snout and large terminal teeth, by attributing to the slender rostrum the 

 function of a prod or rake with which the possessor searched out worms and 

 other soft bodied invertebrates, etc., in the mud of shallow waters while the 

 nares, by virture of their position, were above the surface of the water. 



There is a marked tendency in most of the phytosaurs, a tendency in 

 which M. validus surpasses all other known forms, for the nares to rise on a 

 considerable prominence. This would seem to be a modification entirely 

 uncalled for were the position of the nares due solely to the use of the rostrum 

 as a prod. So situated are the nares in M. validus that it could submerge the 

 body save for the narial hump and lie in wait admirably concealed from its 

 enemies, or more likely, from its prey. Certainly the teeth of this form are 

 more fitted for tearing large vertebrates than for small, mud-burrowing crea- 

 tures. Then too, Machaeroprosopus could scarcely pick small objects from 

 the ground because of the difference in length between the upper and lower 

 jaws. When the jaws were closed the terminal teeth of the lower jaw were 

 functionless and the upper terminal teeth were but little better. It was not 

 until the jaws were wide open that the terminal teeth could be used effectively 

 either as a rake or for seizing any sort of prey. With the jaws separated, 

 however, the upper and lower terminal teeth were directly opposed and admi- 

 rably fitted for seizing and tearing large animals. It seems likely that M. validus 

 was wont to lie in wait concealed close up to the shore in shallow waters ready 

 to seize its prey when the latter came down to drink. Once the prey was 

 dragged into the water it was at the mercy of its captor, for the dentition of 

 the latter probably matched that of any carnivorous land form of the time and 

 the phytosaur had the distinct advantage of being entirely at ease in the water. 



If these were the habits of the more highly specialized phyto- 

 saurs, and the assumption seems logical, the group was remarkably 

 well adapted to the conditions of the times. The adaptation was, 

 moreover, of a very peculiar nature. In most cases adaptations 

 seem to do Httle more than tend to counteract adverse conditions. 

 For instance, the development of speed in ambulatory forms of 



^ Mehl, Bull. Univ. of Oklahoma, op. cit., pp. 23-24. 



