OSTEOLOGY OF CARNIVOROUS DINOSAURS. 

 Comparative measurements oj Antrodemus and Ceratosaurus skulls. 



25 



No. 4734, 



U.S.N. M., 

 Antro- 

 demus 

 vaUns. 



Greatest length of skull, taken at center 



Greatest expanse of paraoccipital processes 



Greatest expanse above center of orbits 



Greatest expanse above center of nares 



Distance from posterior border of orbit to posterior extremity of squamosal. 

 Distance from anterior border of orbit to anterior extremity of premaxillae. 



Distance from extremity of premaxillae to distal extremity of quadrate 



Distance from distal end of quadrate to top of skull '. 



Height of skull over center of maxillary 



Height of muzzle at anterior border of nares 



Height of skull with lower jaw. measurements taken at center of orbit 



Same measurement taken below posterior border of nares 



Transverse diameter of occipital condyle 



Antero-posterior diameter of orbit 



Antero-posterior diameter of narial opening 



Greatest length of quadrate 



mm. 

 605 

 233 

 175 

 40 

 142 

 395 

 C40 

 353 

 215 

 118 



No."4735, 



U.S.N.M., 



Ccrato- 



' sauTus ' 

 naiscornis. 



mm. 

 566 



170 e 



45 « 

 130 

 390 

 640 

 277 

 1.55 

 llOe 

 300 

 135 



40 



73 e 



82 

 212 



e = Estimated. 



LOWER JAW. 



Plates 3-4. 



With the skull of No. 4734, U.S.N.M., only the posterior half of the right ramus 

 is present. In this portion the articular, surangular, and prearticular are clearly 

 determinable as shown in figure 15. A dentary from the same side belonging to 

 specimen No. 8335, U.S.N.M., a slightly larger individual, has been introduced in 

 the restoration of the lower mandible of No. 4734, U.S.N.M. The above-mentioned 

 bones constitute all of the Antrodemus jaw material in the collections of the United 

 States National Museum. As now restored the right ramus has a greatest length 

 of 6S0 mm. 



Dentary {d.). — The dentary of specimen No. 8335, U.S.N.M., on which the 

 present description is based, contains alveoli for 15 teeth, whereas Osborn' has 

 observed 16 alveoli in a dentary' studied by him. These teeth occupy a space 297 

 mm. long. On the internal side the alveolar septa expand into interdental " rugo- 

 sae," similar to those found in Tyrannosaurus and other carnivorous dinosaurs. 

 Transversely the dentary is much compressed, with a slightly thickened and rounded 

 inferior border. Vertically this bone remains about the same depth (65 mm.) 

 until toward the posterior end of the dental series it gradually increases in this 

 diameter. The union with the opposite jaw was probably membraneous, there 

 bemg no indication of a symphysial surface. The anterior end of the ilentary is 

 more angularly truncated than in Ceratosaurus, which presents a more rounded 

 end. The posterior end of this dentary is missing, so that its exact manner of 

 articulation with the surangular, angular, and splenial can not be determined. 

 The principal features of this bone are well shown in figure 15. 



1 Bull. Amer. Mus. .Nat. Hist., vol. 19, 1903, p. 701. 



