FOSSIL I-OOTPRINTS IN Till-: GRAND CANYON 

 OF TI-IF COLORADO, ARIZONA 



By CHARLES W. GILMORF.. 



(.'itralor. Piz'ision of I'crtehratc I'lilcoiitdloi/y. U. S. Ahtliaiui! iMiisciiiii 



Ihc fossil tracks of extinct four-footed animals were first dis- 

 covered in the Grand Canyon of the Colorado in 191 5, Init the al)un- 

 dance of their occurrence and their great diversity of kind remained 

 unknown until 1924. In that year and again in 1926 collections of 

 them were made for the U. S. National Museum, and my studies 

 of these materials have disclosed the ])resence of no less than 26 

 genera and t,2 s])ecies of fossil footprints. In numl)er of species, 

 and in excellence of preservation of the tracks, this area easily out- 

 ranks all other known American localities for Permian and Penn- 

 sylvanian footprints. 



The great antiquity of these fossilized tracks of extinct creatures 

 of a hy-gone age is clearly shown hy the fact that they occur from 

 900 to 3,800 feet below the t()]i of the canyon wall. This means that 

 since the first of these animals left their footprints in what was then 

 moist sand, nearly 4,000 feet of rock-making materials were deposited 

 in successive layers altove them, not to mention the hundreds of 

 feet more that no doubt were eroded from the present rim of the 

 canyon. Add to this ]:)eriod of ui)-l)uilding. the length of time required 

 for the cutting of the canyon through 4,000 feet of solid rock, and 

 we have an idea of the tremendous age of these fossil footprints. 



A third visit to the (irand Canyon under the ausi)ices of the Grand 

 Canyon Fxhibit Committee of the National Academy of Sciences, 

 was made in the late spring of 1927 for the dual purpose of locating 

 and ])reparing exhibits of tracks /;; situ, and making further col- 

 lections of fossil footjirints for the C S. National Museum. Ijoth 

 of these projects were successfully carried out. 



Two small field exhibits, one in the Coconino, the other in the 

 Supai formation were pre])ared, the ])ur])ose being to show the tracks 

 precisely as they occur in nature in order that they may be viewed 

 by visitors, through fixed telescopes which the committee plans to 

 place in front of the new observation station now being erected on 

 Yavajiai Point. In orrler to find suitable locations for these exhibits 



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