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PALAEONTOLOGY: W. K. GREGORY Proc. N. A. S. 
RESTORATION OF CAMARASAURUS AND LIFE MODEL 
By Wiluam K. Gregory 
American Museum of Naturai. History, New York City 
Communicated by H. F. Osborn. Read before the Academy, November 11, 1919 
The muscular restoration of Camarasaurus was preceded by careful 
studies of the consecutive poses of the skeleton of Apatosaurus {Bronto- 
saurus) in three phases of the stride. These poses were worked out in 
a minature model of the complete skeleton, with flexible joints. The con- 
clusion reached is that Apatosaurus was a walking and not a crawling 
quadruped. As compared with living crocodiles the body was well raised 
off the ground in the stride. This is contrary to the ideas of Tornier, 
Hay and others, who advocated a crawling stride. The limbs, however, 
had not the fore-and-aft pendulum action of the perfected mammalian 
quadrupeds; the stride had a wide, lateral swing. 
Subsequently a complete restoration of the musculature of Camarasaurus 
was made in comparison with living reptiles. The prominence of the muscle 
lines is justified by studies of recent alligators, in which certain muscle 
groups stand out as low humps in action. The pose selected was based 
directly on a photograph of a rapidly walking alligator, the right fore foot 
having just descended without the natural continuation of the stride by 
the hind feet. 
The special points noted in the position of the bones of the skeleton are 
the following: Scapula gently, not sharply, inclined backward; inferior 
position of the scapulocoracoid, which was brought relatively near its 
fellow on the opposite side ; spreading upper border of the scapula implying 
an essentially reptilian arrangement of the trapezius and other muscles; 
moderate bending and eversion of the elbow in the stride, the motions of 
the arm bones being essentially similar to those of the crocodiles but with 
the elbow joint less strongly flexed; digitigrade position of the bones of 
the fore limbs and manus. The fore limb as a whole contrasted widely 
with that of the mammal. Pelvic musculature and arch fundamentally 
similar to those of the Crocodilians. At no time did the head of the femur 
fill the acetabulum. The backbone is elevated above the shoulder blade 
in the walking pose. The tail of Camarasaurus is relatively smaller in 
transverse section than that of Crocodilians, with correspondingly weak 
muscles. 
Camarasaurus might well have been an efficient wader. It was positively 
devoid of special adaptations for swimming; the pectoral and pelvic arches, 
and the limbs and backbone were adapted to support the great weight of the 
body presumably on land, as well as in wading; the tail was relatively 
small and feeble. There was a high ratio of limb power to weight. 
The most decisive points in favor of the theory that Camarasaurus 
