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THE AMERICAN MUSEUM JOURNAL 



running habit has evolved independ- 

 ently. The habit has been observed 

 among large tree-living species as well 

 as among lizards of diminutive size, 

 several of the latter frequenting the 

 deserts. The lizard appears incapable 

 of rearing unless moving at a high rate 

 of speed. The bipedal trait may be in- 

 dicated immediately after the begin- 

 ning of the dash over the ground or the 

 lizard may rear upward after it has run 

 a considerable distance. As observed 

 also by the herpetologist, Raymond L. 

 Ditmars, during the reared, running 

 pose the front limbs appear to droop 

 voluntarily and not to be used as bal- 

 ancers, but the position of the tail in- 

 dicates the marked importance of this 

 organ in balancing and there is a 

 voluntary curving upward of the tip of 

 the tail in order to keep the body up- 

 right. From these studies of modern 

 lizards we may picture the running gait 

 of the "ostrich"' dinosaurs, in which the 

 rod-like tail balances the anterior half 

 of the body, the tail being somewhat 

 longer than the backbone in front of it. 

 The hind limbs are relatively longer 

 than in any of the running lizards but 

 relatively shorter than in the ostriches, 

 so that we are not justified in believing 

 that these animals quite attained the 

 remarkable speed of the modern os- 

 trich, which outruns the swiftest horse. 

 The toes of the hind feet of Strufhio- 

 mimiis are purely of the running type 

 and not adapted for scratching or dig- 

 ging. 



Influenced by the fact that the re- 

 mains of these "ostrich mimics" are in- 

 variably found in deposits which had 

 formed ancient seashores, in conjunc- 

 tion with the peculiar structure of the 

 neck and the fore limb, Barnum Brown 

 has suggested that the animal was 

 a wader which fed upon small crus- 

 taceans and mollusks, using its long 



anterior claws partly to scrape the sand 

 away and partly to seize the shore-fre- 

 quenting animals. There are three 

 objections to this theory : first, neither 

 the beak nor the ends of the fingers are 

 adapted for seizing an actively moving 

 crustacean prey of any kind, although 

 they may have been capable of securing 

 the sessile mollusks, which may have 

 been swallowed whole; also neither the 

 structure of the beak nor of the toes is 

 analogous to that of the shore-living 

 birds (Grallatores), which partly live 

 upon small invertebrates. 



Another theory is that suggested by 

 the ornithologist, C. William Beebe, 

 that the fore limbs of the "ostrich mim- 

 ics," feeble as they were, may have been 

 adequate for attacking sandy and grav- 

 elly anthills. The difficulty with this 

 theory is that the terminal bones in 

 both the fore and hind feet do not af- 

 ford evidence of powers for scratching 

 or digging, nor do the upper bones of 

 the fore limb give evidence of accom- 

 modating digging muscles. 



The theory which, on the whole, 

 seems the most probable one is that 

 the "ostrich" dinosaurs were adapted 

 chiefly for an herbivorous browsing 

 pose either among low shrubs or the 

 lower branches of trees. In balancing 

 the body by means of the smaller 

 branches of trees and in drawing down 

 the limbs of trees toward the mouth, 

 the long, sloth-like hands may have 

 been used as the tree sloths use theirs. 

 While the fore limb is quite powerful, 

 it was certainly not adapted to quick 

 movements such as are essential to the 

 capture of an active prey. It must be 

 admitted that no thoroughly satisfac- 

 tory explanation of this limb has yet 

 been suggested ; it is evident that it was 

 ideally adapted for some particular 

 function or habit which had already 

 been assumed in part in the remote an- 



