100 



BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 

 Measurements of dermal plates of Stegosaurus stenops No. 4934- Type. 



Plate 

 No. 



(counting 

 back- 

 ward 



Irom the 

 skull). 



Greatest 

 height. 



Greatest 

 diameter 

 antero- 

 posteri- 

 orly. 



Greatest 

 length 

 antero- 

 posterior 

 of rough- 

 ened 

 base. 



Greatest 

 trans- 

 width 

 or rough- 

 ened 

 base. 



Plate 

 No. 

 (counting 

 back- 

 ward 

 from the 

 skull). 



Greatest 

 height. 



Greatest 

 diameter 

 antero- 

 posteri- 

 orl}'. 



Greatest 

 length 

 antero- 

 posterior 

 of rough- 

 ened, 

 base. 



Greatest 

 trans- 

 verse 

 width 

 of rough- 

 ened 

 base. 



'1 

 2 

 3 

 4 

 5 

 6 

 7 

 8 

 9 



inm. 

 97 

 119 

 134 



172 

 185 



mm. 

 60 

 45 

 82 

 76 

 76 

 191 

 2 323 

 430 



mm. 



mm. 



10 

 11 

 12 

 13 

 14 



3 15 

 3 16 



= 17 

 <18 



2 610+ 



535 

 560 

 610 

 695 

 785 

 630 

 410 

 290 



mm. 

 423 



mm. 

 40 

 55 



36 



17 





590 

 590 

 720 

 450 

 300 

 220 

 U5 



55 

 60 

 96 

 205 

 ISO 











760 

 627 

 335 

 225 

 537 



87 

 105 







105 





60 

 65 



2 610+ 













• Plates with, odd numbers pertain to left row. even to the right row. 

 2 Estimated. 



8 Dermal elements not in sequence. 



* Dermal spine. 



Position of -plate centers in relation to underlying vertebrae. 



Plate 

 No. 



(counting 

 back- 

 ward 



from the 

 skull). 



Vertebrae in vertebral 

 column. 



Plate 

 No. 



(counting 

 back- 

 ward 



from the 

 skull). 



Vertebrae in vertebral 

 column. 



Plate 

 No. 



(counting 

 back- 

 ward 



from the 

 skull). 



Vertebrae in vertebral 

 column. 



1 



2 

 3 



4 

 5 



Atlas. 



Axis. 



Third and fourth (between) . 



Fourth and fifth (between). 



Fifth and sixth (between) . 



6 



7 

 8 

 9 



Sixth and seventh (between) . 

 Eighth. 

 Tenth. 



Thirteenth and fourteenth 

 (between) . 



10 

 11 

 12 

 13 

 14 



Seventeenth. 

 Twentieth. 

 Twenty-fourth. 

 Second caudal. 

 Eighth caudal. 



Morphology of Plates. 



Lull ' has given the following interesting explanation of the development of 

 the dermal plates : 



Upon comparing a given plate with a scute of a crocodile or that of such a dinosaur as Ankylosaurus 

 or Stegopelta it at once becomes apparent that the great expanse of the first represents merely an enor- 

 mous hypertrophy of the median ridge or carina of the latter. This expanse is practically alike on both 

 sides, with blood-vessel impressions and no indication that either one side or the other was in contact 

 with the creature's flesh. On the other hand, the base, the morphological equivalent of the body of 

 the scute in crocodile or Anhylosaur, is always somewhat asymmetrical, even when divided into two 

 portions by the longitudinal cleft of those of the cervical region . This base in the great dermal plates 

 particularly is extremely rugose, implying either a heavy pad of cartilage or a very thick connective 

 tissue between the plate and its underlying skeletal support. There is in no instance any indication 

 of a true articulation with the subadjacent bones. 



1 Amer. Joura. Sci., vol. 29, 1910, pp. 204-205. 



