50 
DESCRIPTION OF THE SKELETON OF HYPACROSAURUS 
Hypacrosaurus altispinus Brown 
PLATES XI AND XII 
Brown, B., Bull. Am. Mus. Nat. Hist., vol. 32, art. 20, 1913, pp. 395-406. 
Referred Specimens: No. 8501, Geol. Surv., Can., consists of the skull, 
right ramus, an articulated series of dorsal, sacral, and caudal vertebrae, 
numerous thoracic ribs, right humerus, ulna, radius, pelvic arch, and 
complete right hind limb and foot. Collected by G. F. Sternberg, 1915. 
Locality: Sec. 6, tp. 33, range 21, W. 4th mer., 3 miles below Tolman 
ferry, left hand side of Red Deer river, Alberta. From 175 feet (aneroid) 
above the river. 
No. 8500, Geol. Surv., Can., consists of a skull lacking the crest, 
both dentaries. Collected by P. A. Bungart, 1915. 
Locality: Sec. 12, tp. 34, range 22, W. 4th mer., 5 miles north of Tolman 
ferry, east side of Red Deer river, Alberta. From 115 feet (aneroid) 
above the river. 
Horizon: Both specimens from the Edmonton formation, Upper 
Cretaceous. 
Generic and Specific Characters: Skull with high, helmet-like crest. 
Narial passages roofed over, external nares opening far forward. Pre- 
maxillaries entering extensively into formation of crest. Dentary deep, 
massive, and carrying 40 rows of vertical teeth. Cervical vertebrae strongly 
opisthocoelous, spines reduced or absent, ribs stout. Dorsal vertebrae 
with centra reduced in size, high massive spines, five to seven times the 
height of their respective centra. Sacrum with eight vertebrae. Scapula 
long and very broad. Radius much longer than humerus. Ischium long 
with closed foramen and large terminal foot-like expansion. Pubis with 
anterior blade short and broadly expanded. Ilium deep and strongly 
curved. Femur, tibia, and fibula of nearly equal length. Pes long and 
massive. 
Skull 
1 
The skull has been entirely freed of the matrix and although the bone 
is in a good state of preservation, below the crest it has suffered consider- 
ably from lateral compression, but more especially from the loss of import- 
ant elements and dislocation of the right maxillary and jugal. The latter 
bones, as the skull is now assembled for exhibition, could not be properly 
articulated, and being pushed forward out of position give the cranium 
an unwarranted depth when viewed from the right side. This is clearly 
indicated in Plate XI, reproduced here from a photograph of the specimen. 
The principal bones missing from the head are the quadrate, jugal, quadra- 
tojugal, and ramus of the left side; the predentary and all the palatal 
elements. 
Viewed in lateral aspect the high, helmet-like crest forms the most 
characteristic and conspicuous feature of the skull of Hypacrosaurus. 
In its great extent and general contour there is a striking resemblance to 
the crest of Corythosaurus from the earlier Belly River formation. The 
crest in this sub-family, as Lambe has clearly and convincingly demon- 
