49 
ON THE SKULL AND SKELETON OF HYPACROSAURUS, 
A HELMET-CRESTED DINOSAUR FROM THE 
EDMONTON CRETACEOUS OF ALBERTA 
In 1913 in establishing 1 the genus Hypacrosaurus on a fragmentary 
skeleton lacking the head, Brown predicted that when the skull was known 
it would prove to be one of the crested forms. His prediction was well 
founded, as is now shown by a specimen in the palaeontological collections 
of the Geological Survey, Canada, which consists of a fairly complete 
skull associated with the greater part of the skeleton. This skull has a 
high, helmet-shaped crest, which in its enormous development closely rivals 
that of the Belly River Corythosaurus , and is the first crested skull of this 
particular type to be discovered in the Edmonton formation. 
The preparation of the specimen has not been completed, but the 
bones most needed for comparison with the type of Hypacrosaurus altis- 
pinus Brown are available and these show such close resemblances in form and 
size as to leave no uncertainty as to their generic identity. The presence 
of a closed foramen in the ischium, coupled with proportionately shorter 
spinous processes on the posterior dorsal vertebrae, appeared at first to 
indicate specific distinctness from Hypacrosaurus altispinus Brown, but 
on my request Dr. W. D. Matthew very kindly re-examined the ischium 
of the type of the above species and under date of February 28, 1923, 
wrote me as follows: “I examined the type of Hypacrosaurus (No. 5204) 
and the ischium is clearly incomplete on the border, as you suggest, so 
there might be an enclosed foramen instead of a notch. The inner half of 
the foramen border is perfect, but proximally and distally it is a broken 
edge and the lines to me look quite conformable to either interpretation — 
a deep notch or an enclosed foramen.” From this it seems quite probable 
that if the foramen in the ischium of the type were perfectly preserved it 
would be closed as in the specimen now before me. Although the spinous 
processes are relatively shorter than those of the paratype discussed by 
Brown, none are completely preserved in the type of H. altispinus, and 
since the specimen now before me closely resembles the type in nearly 
all other particulars, as far as they can be compared, it is identified as 
belonging to that species. 
I wish here to express my appreciation to E. M. Kindle, chief of the 
Division of Palaeontology, and to the other officials of the Geological 
Survey, for the privilege of describing this important and highly interesting 
dinosaurian specimen. The drawings illustrating this paper were made by 
Arthur Miles of the Survey staff. 
*Bull. Am. Mus. of Nat. Hist., vol. 32, Aug. 19, 1913, pp. 395-406. 
