THE SKULL. 



31 



THE CRANIAL ARMATURE. 



Several elements are present in the cranium of Triceratops which seem to have served 

 either wholly or in part as organs of offense and defense. The powerful frontal and nasal 

 horns were most formidable and efficient weapons and must have been of the greatest service 

 to these animals when engaged in resisting the attacks of their enemies, as were also the rostral 

 and predentary bones, which opposed each other and were firmly fixed to the upper and lower 

 jaws, and, like the nasal and frontal horn cores, were in life doubtless insheathed with some 

 horny material which in the latter elements probably resembled very closely the horns of the 

 recent Bovidse and other cavicom Mammalia. The rostral and predentary coverings were 

 perhaps not very unlike those enveloping the beaks of the modern turtles, and doubtless served 

 the animal both as organs for procuring food and as weapons. It is probable that the primary 

 function of the enormously expanded parietals and squamosals was to afford protection to 

 the cervical region, while at the same time counterbalancing the weight of the exceedingly 



apf 



Fig. 28.— A, Internal view of left premaxillary of type of Triceratops flabellatus Marsh, No. 102i ; Yale Museum; B, internal view of right 

 premaxillary of same; C, external view of right premaxillary. n, Surface for nasal; mx, surface for maxillary; pmx, surface for opposite 

 premaxillary; r and sr, surface for rostral; ipf, interpremaxillary fontanelle; /, foramen leading to interparietal fontanelle or fossa; apf, 

 anterior palatine foramina. One-eighth natural size. 



massive frontal region, including the horns, and giving greater surface for the attachment of 

 those muscles necessary for controlling the movements of the enormous head. In addition 

 there was a series of little, elongated, triangular pointed ossicles (epoccipitals) attached to the 

 free margin of the frill and giving to this border a peculiar undulating appearance, while a 

 similar ossicle, the epijugal, was attached to the external surface, of the distal end of each jugal. 

 In addition to the protective elements already mentioned, many of which, it is clear, 

 were developed primarily for protective purposes, all the elements of the skull are especially 

 heavy and are firmly united with one another by sutures, many of which become closed in 

 the old animal, thus giving a degree of rigidity and strength to the cranium quite unknown 

 in other dinosaurs and affording the greatest possible protection. From the texture of the 

 external surface of all the cranial elements it is evident that they were invested with an 

 integument similar to that which covers the skull in most recent turtles, instead of being deeply 

 embedded in flesh and poorly protected by a thin skin. Such a covering would serve as an 

 additional protection to the animal. 



