PARjISUCUIA 187 



The Aetosauria, which have long been known from a marvelous 

 specimen found in Wiirtembcrg many years ago and described by 

 the elder Fraas, need not detain us long. They were relatively 

 small reptiles about two feet long, almost completely incased in a 

 bony armor, and purely terrestrial in habit. The skull even yet 

 is not perfectly known, and it is possible that when it is the group 

 may have to be dissociated from the phytosaurs. The nostrils 

 were not posterior, and the skull is short. Other specimens of the 

 same group have been described from the Upper Triassic rocks of 

 Massachusetts. 



The Pelycosimia of Huene are very interesting as showing 

 apparently primitive forms with which the true phytosaurs may 

 have been intimately related ancestrally. They, too, have a rather 

 short skull with the nostrils in front, and were not at all aquatic in 

 habit. Not much is known about the single genus that is located 

 in the group, aside from the skull and a few limb bones. 



PHYTOSAURIA 



The Phytosauria, so far as known, were all reptiles of consid- 

 erable size, greatly resembling the crocodiles, and especially the 

 gavials in form and habit, but differing very greatly in having the 

 external nostrils situated far back near the eyes; in having no 

 false palate so characteristic of the Crocodilia; in having a more 

 primitive shoulder-girdle, consisting of a short coracoid, inter- 

 clavicle, and clavicles; and in having the ordinary t\-pe of pelvis, 

 that is, with the pubis entering into the acetabular articulation 

 for the femur. They were all, like the crocodiles, covered more or 

 less by a bony armor; there are two openings on each side of the 

 temporal region; there is no pineal Opening; the vertebrae are 

 gently biconcave, precisely like those of the early or mesosuchian 

 crocodiles; there is always an opening of considerable size, called 

 the preorbital foramen, in front of the eyes, as in some crocodiles, 

 many dinosaurs, and most pterodactyls; there is also an opening 

 through the back part of the mandibles as in crocodiles; and the 

 double-headed ribs are attached exclusively to the transverse 

 process of the arch, precisely as in the crocodiles, dinosaurs, and 

 pterodactyls. From all these it is evident that the phytosaurs are 



