52 



GIJIDEBOOK OF THE WESTEEX UNITED STATES, 



United States National Museum.* The largest animals that haA^e 

 ever been found lived at a time when reptiles were the ruling types 

 of animals in the sea^ on the land, and in the air. Flying reptiles 



* Como Bluff is classic ground to those 

 interested in the fossil remains of animals 

 that inhabited this region long ages ago^ 

 for it "Was here that the first dinosaur hones 

 were discovered in the Rockv Mountain 

 region. In 1876 Mr, W. IT. Reed, now a 

 professor in the University of Wyoming 

 but then in the employ of the Union Pa- 

 cific Co. , found in the bluff above the now 

 abandoned station of Aurora a large petri- 

 fied limb bone, which he sent to Prof. 

 O. C. Jlar^h, of Yale University. Prof. 

 Marsh at once recognized the fossil as be- 

 longing to some unknown extinct animal 

 and immediately enlisted the services of 

 Mr. Reed. Collecting was actively car- 

 ried on here for a period of ten years or 

 more, and as a result of this work Prof. 

 Marsh was able to publish the remarkable 

 series of restorations of dinosaurs which 

 appeared from time to time in several 

 pubUcations. 



So famous did these fossils become that 

 in 1S99 the officials of the Union Pacific 

 Railroad invited the geologists of the 

 country to visit the places where the 

 bones were found. An expedition con- 

 sisting of geologists from universities and 

 museums in many parts of the United 

 States visited Como Bluff, the Freeze- 

 out Hills, and other famous ios^il locali- 

 ties. So well known are the bone beds at 

 Como Bluff that some have called the beds 

 the Como formation. However, in the 

 same formation at Morrison. Colo., simi- 



7 



lar bones were found, and the formation 

 was named Morrison — a name which is 

 now generally accepted. Some of the 

 dinosaurs were the largest land animals 

 that ever walked the earth, and some 

 were very diminutive. They differed 

 greatly in size, shape, structure, and 

 habits. Some were plant eaters; others 

 fed on fledli. Some walked on four feet; 

 others with small, weak fore limbs walked 

 entirely upon the strongly developed hind 

 1^. Some had reptUe-like feet; others 

 wero bird footed. Some had toes pro- 

 vided with long, sharp claws; others had 

 flattened hoof-like nails. There were di- 



nosaurs with small heads and others with 

 large heads. Some were large and cum- 

 bersome; others were small, light, and 

 graceful and so much resembled birds in 

 their structure that onlv the skilled 

 anatomist can distinguish their remains. 

 Some of enormotis size were clad in coats 

 of bony armor, which gave them a most 

 bizarre appearance. 



The largest herbivorous or plant-eating 

 dinosaur whose fossil remains have been 

 found in Como Bluff was the huge Bron- 

 tosaurus, or thunder lizard, as it was 

 called by Prof. Marsh. It was 70 feet 

 long, stood 16 feet high at the hips, and 

 had a long tail, an equally long neck, and 

 a head that was only a little larger than 

 that of a horse. The weight of such a crea- 

 ture has been variously estimated at IS to 

 20 tons. This animal doubtless lived on 

 the luxuriant tropical vegetation, but how 

 its enormous bulk could be sustained by 

 such food as could pass tlirough its ridic- 

 ulously small mouth has caused much 

 wonder. It is not certain whether the 

 name thunder lizard was given to it be- 

 causa of its size or because of the large 

 sum— over $10,000— which Prof. Marsh 

 spent in excavating and preparing It. 



Some dinosaurs that iire even larger 

 than the brontosaur have been found 

 more recently. A Diplodocus now in the 

 Carnegie Museum in Pittsburgh had the 

 enormous length of 8 IJ feet. The size of 

 the fosHI bones is indicated in the accom- 

 panjdng figure 9. 



At the time these animals flourished the 

 Rocky Mountain region was a low, nearly 

 level country-, covered with tropical vege- 

 tation, with many wide, shallow streams 

 and swampy areas, thus- f urm^hing a con- 

 genial place for these sluggish swamp- 

 inhabiting creatares to wade lazilv about 

 or float in the water, for it has. been 

 deemed improbable that the enormous 

 bulk of some of them could be sustained 

 without lateral support such.as would be 

 obtained in water. 



^ One of the most striking of the vegeta- 

 rians of this period was the Stegosaurus, 



