April, 1921. 



Thk Canadian Fielo-Xatikalist. 



65 



case floated al)Ont before reachinjr its 

 final refiting-plaee. 



The third family of herbivorous dino- 

 isaurs found in the deposits along the 

 Red Deer river is the armored or plated 

 dinosaurs. They were low, heavy-boned, 

 quadrupedal, laud animals witli very 

 short massive limbs. The feet were short 

 and stubby and somewhat resembled the 

 feet of a rhinoceros. The ribs were so 

 constructed and articulated as to throw 

 them well out and give a broad back and 

 a large body cavity much the shape of a 

 huge barrel. The hips were as much as 

 five feet broad though the animal Avas not 

 more than six feet high. 



These dinosaurs were completely incased 

 in dermal armor or bony scutes in the skin. 

 I n some genera the scut-es were high-keeled, 

 thick and as much as a foot and a half in 

 length, while in other genera they were 

 more plate-like with only slightly elevated 

 keels. The larger scutes were arranged in 

 rows along the back and sides while on the 

 under parts were ossicles of irregular shape 

 which protected the animal much as the 

 (rhain armor protected the warrior of the 

 middle ages. Between the large scutes 

 were smaller ones and in the smaller in- 

 tervening spaces were tiny ossicles similar 

 to those on the under parts. It is ({uite 

 evident that these creatures were so ef- 

 fectively armored that they need have no 

 fear of their enemies. The tail terminated 

 in a bony club, about the size of a water 

 pail, which was made up of a number of 

 modified dermal scutes thoroughly fused 

 together. The eyes were protected by a 

 bony lid, and in at least one genus iPano- 

 plosaurus) even the mouth was protected 

 by a plate of bone in the cheek, which Mr. 

 fjambe has called the dental plate. The 

 members of this family also possessed a 

 horny beak. These animals were so -well 

 protected that tliey did not need speed as 

 a means of escape and so became a heavy 

 sluggish animal in wliieli the main dinelo])- 

 ment was strength to carry the heavy load. 



The armored dino.saurs had an excep- 

 tionally small l)i'ain, -the cavity being 

 smaller than a man's fist. The neural 

 canal was greatly expanded within the 

 sacrum, and Prof. Marsh thought that this 

 was the seat of that part of the brain which 

 controlled the action of the animal. 



There are at leat four genera of car- 

 nivorous dinosaurs represented in these 

 rocks, the largest of which is Gorfjosaunis. 

 While Gorgosaurus attained a lengtii of 

 thirty feet there was a contemporaneous 

 carnivore which was probably not more 

 than eight or ten feet long. Only frag- 

 ments of the latter have been found and 

 it has not been described. 



Gorgosaurua had a much lighter frame 

 than the herbivorous forms and the limb 

 bones were hollow. The bones show many 

 well-developed areas for the attachment of 

 muscles. No doubt Gorgosaurus was much 

 more active than the herbivorous forms, 

 but of course was too heavj- to be agile. 

 The smaller forms were probably much 

 more active. 



The carnivorous forms walked on their 

 hind feet only, and used their huge tails 

 as balancing organs. The front limbs were 

 very small, specially in Gorgosaurus, and 

 could have been of little use. This limb 

 was becoming vestigial as shown by the 

 study of earlier carnivorous dinosaurs. 

 The fore-limb possessed only two func- 

 tional digits and one metacarpal which 

 was vestigial, while the hind foot had 

 three well developed and powerful toes 

 and a smaller one at the back .similar to 

 the back toe of a turkey. The fifth toe 

 was represented by the proximal part of 

 the metatarsal. The terminal phalanges 

 each bore a powerful claw. Gorgosaurus 

 had four powerful jaws in which were more - 

 than sixty sliarp, double-edged, recurved 

 teetli, some of which were ffinr indies long. 

 It must have been a fieiv-e looking lizard 

 as the name implies. 



Mr. L. M. Larabe suggested that Gorgo- 

 saurus may have been a .scavenger, since 

 the teeth of the type s])ecinien showed no 

 sign of wear. 



Another fairly well-known genus is Or- 

 nifliomiiius which was much smaller and of 

 more slender construction than Gorgosau- 

 rus. 



The carnivorous dino.«;aurs were not 

 fitted for life in the water. 



Ertiuctiou. — It is impossible to say what 

 eansed the etxerminatiou of the dinosaurs. 

 Changing conditions with the cutting off 

 cf their food snnply and their inability to 

 migrate great distances may have been one 

 cause. The rise of the mammals with their 



