OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



103 



FORE LIMB AND FOOT. 



The fore limb of Ceratosaurus is relatively of small size, with a very short foot 

 as compared with the greatly lengthened hand in Anirodemus. There were four 

 digits in the manus, of which the two median ones are the more robust. The 

 phalangial formula is unknown, though it has been restored (largely following 

 Marsh) on the mounted skeleton (pi. 30), as 2, 3, 3 1. From the evidence of 

 known Theropod fore feet it would appear more in accord 

 if given 2, 3, 4, 2 or 3. 'The humerus and ossified carpus 

 of Ceratosaurus are unknown. 



Ulna (u.)'. — The ulna and radius were found in place as 

 shown in figure 60, nearly in articulated position as related 

 to one another and also in reference to the accompanying 

 metacarpals. 



The ulna lacks a considerable section of the shaft but 

 the total length may be considered correctly determined since 

 the proximal and distal ends were found retained in rock. 



The proximal end is widely expanded and roughly trian- 

 gular in cross section. The anterior face is hollowed out 

 for the close approximation of the head of the radius. 

 There is a prominent olecranon process (fig. 59), which in- 

 creases the length of the bone posteriorly. It is also robust 

 and shorter than in Antrodemus. The distal end is only 

 slightly expanded, the articulating surface being convex, 

 while the whole end lacks the great obliquity of the Antro- 

 demus ulna. 



Comparative measurements of ulnae of Ceratosaurus and Antrodemus. 



Fig. 59.— Left ulna of Cera- 

 tosaurus nasicornis Marsh. 

 Type— No. 4735, U.S.N.M. i 

 nat. size. Viewed from the 

 back. 0, olecranon. 



Greatest length of ulna 



Greatest transverse diameter of proximal end 

 Greatest transverse diameter of distal end 



Antrodemus 



valens, 



No. 4734, 



U.S.N.M. 



263 

 90 

 55 



Radius (r.). — The shaft of the radius of Ceratosaurus has been so flattened bv 

 crushing that its transverse diameters are greatly exaggerated. The proximal end 

 is elongated transversely (fig. 61), the articular surface shallow^ concave in the 

 same direction. The less expanded distal end is subcircular in outline and shallowly 

 cupped. On the ulna side of this end is a flattened area that in life was probably 

 closely opposed by the ulna. The distal end in relation to the longer axis of the 

 bone is squarely truncated, there being no indication of the obliquity found in the 

 radius of Antrodemus. 



The radius of Antrodemus is nearly half again as long as that of Ceratosaurus, 

 the proportion being as 1 :: 1.48, but the relative proportions of length of radius to 

 length of ulna is exactly the same in both genera. 



