316 It. S. Lull — Stegosmirus nngulatus 3larsh. 



savannas * "^" * conditions donbtless similar to those now 

 found about the mouth of tlie Amazon and over some of the 

 more elevated plains of western Brazil." In spite of the 

 numerous rennxins of plant-feedini>' animals, the actual relics of 

 fossil plants are relatively few, nor does the sediment in which 

 these remains are found give other evidence of abundant vege- 

 tation. Hatcher's inference of "luxuriant forests" is, there- 

 fore, as yet unproved by direct evidence. 



The water areas, as lias been shown,* were doubtless the 

 dwelling places of the huge contemjjoraneous Sauropods, while 

 Stegosaurus was terresti-ial and possibly frequented the forests 

 in search of the tender bnt luxuriant vegetation upon which it 

 browsed. It may well be that the extreme relative narrowness 

 was an adaptation to forest conditions and afforded ease of 

 ])assage between the trunks of the tree ferns, conifers, an'd 

 other vegetation of that day. Stcgosmin/s is rarely found 

 entombed with sauropod dinosaurs, but, on the contrary, is often 

 found isolated or in company with the bipedal unarmored her- 

 bivorous Ccunjytosanrus, the nearest equivalent of the European 

 Jguanodon, and with the iieet Dfijoscmrus ; and of carnivores, 

 the agile Coelui'us and the blood-thirsty Allosaurus^ which was 

 probably its greatest enemy. 



I imagine much of the bizarre character of the armor of 

 Stegosaurus was due to the over-specialization accompanying 

 racial old age, but it was nevertheless in many respects admir- 

 ably adapted to meet on a more or less equal footing the huge 

 well-armed carnivore last mentioned. It would seem as though 

 Stegosaurus, instead of presenting his front to the enemy, turned 

 the rear, possibly crouching low in front as the crocodile does, 

 and, with vigorous sweeps of the terrific tail, impaled the exposed 

 ventral portion of the bipedal carnivore upon the caudal spines 

 and sharp-edged plates. 



The long hind limbs imply a rather rapid pi'ogression, while 

 the powerful fore limbs Avere not only for locomotor purposes 

 but for rapidly pivoting the body to prevent either a frontal 

 or flank attack. 



Of the evolutionary history of Stegosaurus, we know but 

 little. It seems, however, to have been a migrant from Eu- 

 rope, having its nearest relative in Omosaurus {Dacentrurus), 

 remains of which are known as far back as the Dogger (Bath- 

 onian) of England. 



In Omosaurus durohrivensis i\'o\n the Oxfordian of England, 

 which I studied this summer in Cambridge and in the British 

 Museum of ]!^atural History, I find what may readily be a 

 direct ancestor of the American types. The plates and spines 



*Lull, Dinosaurian Distribution, this Journal, xxix, p. 10, 1910. 



