OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



101 



The anterior chevrons of 'Ceratosaurus are especially long, slender, and with but 

 slight backward curve. They articulate intervertebrally with beveled articular 

 facets on the ends of jjthe!|] centra. 

 They begin between the first and 

 second vertebrae and continue 

 to the forty-first caudal. The 

 second, the longest one of the 

 series, measures 254 nam. in 

 length. The haemal opening 

 between the branches forming 

 the Y-shaped proximal ends are 

 very much constricted trans- 

 versely. The proximal end is 

 very slightly expanded, but it 

 forms a bridge across the upper 

 boundary of the haemal open- 

 ing. These chevron bones of 

 Ceratosaurus can be readily dis- 

 tinguished from the homolo- 

 gous elements of other American 

 Theropodous dinosaurs by 

 their greater relative length and 

 slenderness, and by the very 

 slight expansion of their proxi- 

 mal and distal ends. 



The distal series are short, 

 with expanded free ends that 

 curve decidedly backward. 

 Chevrons 29 to 34, viewed from 

 the side, show a spur-like pro- 

 longation that extends well up- 

 ward between the two centra. 

 In a lesser degree the anterior 

 chevrons of Tyrannosaurus 1 

 have a somewhat similar devel- 

 opment, as they do also in Gor- 

 gosaurus libratus Lambe. 2 



RIBS. 



Thoracic ribs. — The thoracic 

 ribs of Ceratosaurus are un- 

 known at this time, except the 

 right articulating with presacral No. 21, shown as found in position in plate 21, 

 figures 1 and 2. 



Fig. 58.— Left fore limb and foot of Ceratosaurus nasicornis Marsh. 

 Cat. No. 4735, U.S.N. M. Type. About | nat. size. Viewed 

 from the front. Greater part of the coracoid, distal end of 

 scapula, humerus, carpus, and terminal phalanges of Ceratosau- 

 rus unknown. These are restored here from allied forms. 

 This figure was first published by Marsh as the fore limb of 

 Allosaurus fragilis. (After Marsh.) 



i Osborn, H. F. Bull. Amer. Mus. Nat. Hist., vol. 35, 1917, pi. 27. 

 2 Lambe, L.M. Mem .100 Geol. Surv. Canada, 1917, fig. 49. 



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