64 



BULLETIN 110, UNITED STATES NATIONAL MUSEUM. 

 Phalangial formulae of various Theropod dinosaurs. 







Digits 











Name. 













Formation. 



Remarks. 















I 



2 

 2 



2 

 2 



2 

 2 



2 



2 



2 



2 



II 



3 

 3 



3 

 3 

 3 

 3 



3 

 3 



3 

 3 



III 





 3 



4 



4 

 4 

 4 



3 



4 



4 

 4 



IV 





 1 





 

 

 3 





 2 



3 

 



V 







Gorgosaurus libratus Lambe 



Ceratosaurus nasicornis Marsh . . 



Ornitholestes hermanni Osborn. . 

 Antrodemus valens Leidy 





 





 

 

 







1 



1 

 



Belly River 



Morrison 



do 



do 



Skeleton in Museum Geol. 



Surv. of Canada, No. 2120. 

 Mounted skeleton in U.S.N. 



M. Cat. No. 4735 Marsh's 



fig. PI. XI, D. of N. A. 



(Allosaurus fragilis). 

 Mounted skeleton in A.M.N. 



H. No. 587. 

 Mounted skeleton in A.M. 



Antrodemus valens Leidy 



Hallo-pus victor Marsh 



do 



Jurassic 



.....do 



N.H. 

 Skeleton in U.S.N.M. No. 



4734. 

 Evidence for formula un- 



Compsognathus longipes Wag- 

 ner. 

 Anchisaurus polyzeius Marsh 



Anchisaurus colurus Marsh 



known. Specimen in' Yale 

 University. 

 From Marsh's restoration of 



Triassic 



do 



the skeleton. 

 Formula that of restoration 



by Marsh. D. N. of Amer. 



Skeleton in Yale Museum. 

 Skeleton in Yale Museum. 



Ornithomimus (Struthiomimus) 

 altus Lambe. 



Belly River 



Mounted skeleton in A.M. 

 N.M. No. 5339. 



The more important progressive changes that have taken place in the 

 specialization of the fore limb and foot in the carnivorous dinosauria during 

 successive geological periods appears to be: (1) Reduction in the number of digits, 

 (2) elongation of the penultimate phalanges, (3) lengthening of the scapula, 

 (4) shortening of the forearm, (5) relative reduction in size of the entire fore limb. 



With the exception of Ceratosaurus which has both inner and outer fingers 

 reduced, all of the other known carnivores show that the reduction in the number 

 of digits takes place on the outside of the foot. Beginning with the oldest known 

 Theropods from the Triassic all are found to possess the full complement of five digits, 

 though the fifth is often rudimentary. In the Jurassic we find in Ornitholestes that 

 the fifth digit has entirely disappeared, and the fourth is only represented by a 

 vestigal metacarpal. Antrodemus appears to have gone still farther, and apparently 

 the fourth has been lost and the third is somewhat reduced, and approximately 

 the same condition obtains in the hand of Compsognathus from the Upper Jurassic 

 of Bavaria. 



Our knowledge of the manus in the Cretaceous Theropodous dinosaurs is rather 

 meager at this time, but a specimen recently described by Lambe 1 (Gorgosaurus 

 libratus) from Upper Cretaceous (Belly River) shows a still further reduction, there 

 being only two functional digits, the third being represented by the vestigal metacar- 

 pal only. 



i Ottawa Naturalist, vol. 28, 1914, pp. 13-17; Memoir 100, Geol. Surv. Canada. 1917, pp. 52-57, figs. 33-36. 



