36 J2. S. Lull — Dinosaurian Distribution. 



conditions and necessarily went where food was abundant and 

 were checked where it failed. The opportunity for migration 

 to Gondwana Land from Enrope by a dry land route may 

 readily have ceased before the Orthopoda reached the Old 

 World. The Sauropoda, on the other hand, being amphibious 

 could cross broken land connections provided the water were 

 not of too great an extent. It is a significant feature that only 

 Theropods, Sauropods and the late Cretaceous Orthopods, 

 Olaosaurus and Trachodon, have been found in marine 

 deposits, indicating a semi-aquatic life on the part of the latter 

 two and at least a fearlessness of water when necessity arose upon 

 that of the carnivores. By the time the Trachodont dinosaurs 

 reached the Old World the opportunity for southern migration 

 even for an amphibious animal had apparently ceased. . 



A comparison may well be made with living mammals, the 

 deer on the one hand, the hippopotamus on the other. The 

 former are world-wide in their distribution except for 

 Australasia, the Arabian peninsula and Africa, save for a sin- 

 gle species, Cervus ha?>harus, which inhabits the Mediterranean 

 coast from Tunis to the slopes of the Atlas range. Schillings 

 (1906, p. 261) says : "In 1896 hippopotamuses were still plentiful 

 in the Nzoia River and the Athi River in British East Africa; 

 they were to be found, too, along the coast between Dar-es- 

 Salaam and Fangani. I saw them on several occasions in the 

 surf, and I shall never forget my astonishment once, on get- 

 ting out of a chimp of cocoanut palms, to see what I had 

 imagined to be an uprooted tree trunk on the sands suddenly 

 change into a hippopotamus and make its way into the sea. 



"Hippopotamuses travel by sea to get from one estuary to 

 another, no doubt ridding themselves at the same time of 

 certain parasites in the salt water." 



Hippopotamuses show no more aquatic adaptation than the 

 sauropod dinosaur, Diplodocus, if as much. Hippopotamuses 

 are confined in their present range to Africa south of the 

 Sahara, being found in the Nile only above Khartum. In 

 former times they extended to Madagascar, northwest 

 India and practically the whole of western Europe including 

 southwest England (Murray 1866, map XXIX). This shows 

 that certain barriers exist which prove effective against such 

 extremely mobile creatures as the deer and which have 

 debarred them from the Ethiopian realm. These barriers, 

 however, were not prohibitive in the case of the less mobile 

 hippopotamus. A similar contrast of conditions might readily 

 have limited the distribution of the Orthopod dinosaurs, while 

 the Sauropoda, as in the case of the hippopotamuses, could 

 easily migrate. 



