April, 1921. 



The Canadian Field-Naturalist. 



63 



similar habitat iiidicaties that the climate 

 was semi-tropical. 



This must have beeu a muc)i favoured 

 Ihaunt of dinosaui-s and other reptiles, 

 for there are thousands of individuals 

 represented and. of course we see only a 

 very small percentaj^e of the bones that 

 were entombed in tlie rocks. 



As the animals died on the banks of 

 a river or lake or on a delta, the flesh 

 was torn off by some hungry carnivore 

 and tjhe bones scattered. In times of 

 flood these bones wei^e picked up and 

 caiTied to some lake or washed upon a 

 mud-flat or isiand^bar. There are a great 

 many extensive "bone beds" or layers 

 in wlhich thousands of bones have been 

 deposited, as driftwood would be thrown 

 up on a beach by the waves, or carried 

 on to a mud-flat b.y back water. These 

 bone beds are usually aJt the junction of 

 the clay and sand rather than wholly 

 within either type of deposit. The bone's 

 in these deposits are usually disarticula- 

 ted and sihow signs of having been tossed 

 about by the waves. 



Besides these bone beds many skulls 

 and skeletons were deposited more or less 

 complete. Some of these seem to have 

 been washed upon a beach or mud-flat 

 and after the lower jtialf was covered 

 with sediment the exposed portion was 

 torn away by some carnivore leaving 

 only half of the skeletion to be preserved. 

 In other cases the animals were mired 

 or the carcases were washed into quick- 

 sand or on to mud-flats where the car- 

 nivora could not reach them. One skel- 

 eton collected shows tjtie remains of rushes 

 which grew among the undisturbed bones 

 and even the skin impression is preserved. 

 It is very common to find skeletons 

 mingled with the remains of vegetation 

 such asi ruslhes, moss, leaves and branches 

 of trees. The animals wlhich spent most 

 of their time in t^e water are better 

 known than those which habitually lived 

 on land, because after death tilieir bodies 

 often floaited into some lake or bayou 

 beyond the reaelh of the eamivora and 

 were buried intact. 



Kinds op Canadian Dinosaurs. — Of 

 the dinosaurs thati have left tjfieir bones 

 entombed in the Belly River and Edmon- 



ton formations along Red Deer river, 

 Alberta, the best known are divided into 

 four families. The most common is that 

 of the duckbilled dinosaurs or Hadro- 

 sauridae. Of this family nine genera 

 have been collected from Alberta, eight 

 of whiclh have not been foiind in ot^er 

 deposits. Next in number comes the fam- 

 ily of horned dinosaurs or Ceratopsia 

 of which two genera have been described 

 from the Edmonton and five from the 

 Belly River formations. None of these 

 are known from any other age. The 

 armored dinosaurs or Ankylosauridue are 

 not as well known as the above-mentioned 

 families, T/ie carnivorous dinosaurs be- 

 long to a different sub-order, Tlhey do 

 not possess a predentary (a bone situated 

 in front of the dentary or lower jaw) as 

 do the above-mentioned families. None 

 of the very large or very small dino- 

 saurs have been found in these deposits. 

 They have been found only in older 

 deposits than those represented on the 

 Red Deer river. 



The duck-billed dinosaurs were heavy- 

 boned creatures wjriieih ranged up to forty 

 feet in length. The legs were of unequal 

 size, the hind pair being the larger. The 

 fore-feet had four toes and the hind 

 ones three. The terminal phalanges of 

 tihe toes of t^e hind feet and part of 

 those of the front feet bore hoofs. All 

 four feet were webbed. The tail, which 

 comprised about half the length of the 

 animal, was high and narrow, making 

 a powerful swimming organ. The integ- 

 ument was made up of small scales, (non- 

 imbricating and polygonal) wthich were 

 little thicker than the scales of a snake. 

 At certain intervals tihere were areas of 

 larger scales or raised bosses whic^i varied 

 in shape and arrangement in different 

 species. It is probable that wit^i this var- 

 ied skin pattern there was a varied color 

 pattern whieji may have been quite orna- 

 mental. The thin skin and absence of any 

 means of defence, coupled with the web- 

 bed feet and swimming tail, seem to 

 prove beyond a doubt tliat these dino- 

 saui-s spent most of their time in the 

 water or at least took to tlie water for 

 protection from their enemies. The pre- 

 raaxillae and predentaries were expanded 

 and incased in a horny sheath similar 



