826 R. S. LULL 8AUR0P0DA AND STEGOSAURIA OF THE MORRISON 



The liribitat is also open to qiu'stioii, though, as I have sliowii. the 

 Saurojioda and Predentate dinosaurs seem to have oeeupied dilTerent 

 habitats — the one amphibious or aquatic, the other in the main terrestrial ; 

 fur in no other way can we account for the marked differences in distri- 

 bution of the two orders, which, reduced to a final anal3'sis, have gone so 

 far thnt the two groups are rarely found in the same quarry, even within 

 the same region and geological formation. This statement is, however, 

 in part refuted by Hennig, who remarks that at Tendaguru, German 

 East Africa, such limitation does not hold, as the occurrence of Sauro- 

 poda and Stegosaurs seems rather to be a uniform one throughout. 



In the genus Stegosaurus, which is perhaps the best known and least 

 understood of armored dinosaurs, the evidence of imperfect limb articu- 

 lation, which was given as partial evidence for aquatic life on the part 

 of the Sauropoda, is also seen, though to a less txtent. There is in 

 Stegosaurus a powerful, laterally compressed tail, with long neural spines 

 above and chevron bones below, which would serve as a very efficient 

 swimming organ were the burden of armor plates and the rigidity of the 

 body not too great a handicap to semi-aquatic life. 



Migratory Roads 



Both groups of dinosaurs were great travelers. I myself ha\ c followed 

 their migrations over thousands of miles of the earth's broad surface. 

 W'itli the Sauropoda the route may have been along the continental mar- 

 gins from home to home, miu-h as in the case of the hippopotami today, 

 which, though denizens of the African streams, nevertheless swim boldly 

 out to sea from river mouth to river mouth and thus pass by the inhos- 

 pitable regions which would otherwise effectually bar their progress. In 

 this way the occurrence of Sauropod remains in marine or brackish water 

 sediments in Madagascar and East Africa may perhaps be partially ex- 

 plained. The Predentates as a whole, however, seem to have chosen- the 

 lar^d route, and their lines of migration will be less surely traced even 

 with the increase of our knowledge. This route distinction, however, may 

 account for the peculiar faunal likenesses and unlikenesses between Eu- 

 rope, America, and Africa, which have yet to be told. 



Geographic and Geologic Disteibution 



savroi'oda 



Geographically the Sauropoda were a very wide-spread race, being 

 exceeded only by the carnivorous dinosaurs in the extent of their wander- 



