39 
MUSCULATURE AND FUNCTION IN THE CERATOPSIA 
By Loris S. Russell 
Illustrations 
Page 
Figure 1. Protoceratops andrewsi Gregory and Granger 40 
2. Chasmosaurus belli (Lambe) 40 
3. Styracosaurus albertenm Lambe 41 
4. Centrosaurus fiexus (Brown) . . . . 41 
5. Anchiceratops longirostris Sternberg 42 
6. Triceratops sp 42 
7. Chasmosaurus belli (Lambe) 43 
8. Chasmosaurus belli (Lambe) 45 
9. Chasmosaurus belli (Lambe) 46 
The present paper is the outcome of an attempt to construct a life 
model of the homed dinosaur Chasmosaurus belli (Lambe) . It was decided 
to prepare this model by a detailed reconstruction of the muscular system, 
a method that has been used in dinosaur restorations by Lull, Osborn, 
Gregory, and Romer, In addition to studying the methods and results of 
these workers, the writer made a complete muscular dissection of Sphenodon , 
using the monograph of Osawa (5). A partial dissection of the alligator 
was also made, to supplement the excellent account of the pelvic region 
given by Romer (6). The muscular anatomy of the bird was studied in 
Shufeldt’s text (8) on the raven, which is very complete but lacks the com- 
parative viewpoint. With this information obtained, a scale model of the 
Chasmosaurus skeleton was prepared, and upon this the principal muscles 
were reconstructed. The finished restoration, with its clothing of integu- 
ment, was figured recently by Lull (3, Plate 17) . 
Some students think that such restoration methods are unnecessarily 
elaborate and probably no more accurate in results than the simpler pro- 
cess of modelling the animal directly from the skeleton. The writer admits 
that muscular reconstructions are more or less controlled hypotheses, hav- 
ing a debatable degree of accuracy, but it is contended that the restora- 
tions made by this method are at least plausible and life-like. More im- 
portant, however, than the finished model are the ideas regarding move- 
ment and function that emerge during the reconstruction. It is the purpose 
of this paper to describe the probable form and function of the more im- 
portant muscles in Chasmosaurus and other ceratopsians, and to deduce 
therefrom certain conclusions regarding the palseobiology of the homed 
dinosaurs. 
The writer is indebted to Professor R. 8. Lull for helpful criticisms. 
THE HEAD 
Lull (2) has given a very good account of the probable cranial muscu- 
lature in Triceratops. This genus is the end member of the series, with 
certain specializations carried to the extreme. Chasmosaurus offers a sort 
of intermediate stage in the evolution of the ceratopsian skull. 
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