58 



BULLETIN 89, UNITED STATES NATIONAL MUSEUM. 



Caudal vertebrae. — In the paleoutological collection of the National Museum 



there are no less than 7 articulated series of caudal vertebrae, in addition to a great 



number of detached elements. Although none 

 of these series represent a complete tail, they at 

 least supplement one another to such an extent 

 that a very correct idea can be obtained of the 

 entire caudal region of Stegosaurus. 



With specimen No. 4934 there are 22 cau- 

 dals preserved, 17 being articulated with the 

 sacrum. The remaining 5 are disarranged, but 

 doubtless represent the next of the series. 

 Specimen No. 4714 has 44 vertebrae in series 

 beginning with the fourth and continuing to the 

 very tip (see fig. 58). A smaller individual, No. 

 6531, has 40 caudals present, and it appears that 

 4 or more 

 are miss- 

 ing from 

 the prox- 

 imal and 

 perhaps 

 an equal 

 number 

 from the 



distal end of the series. The other specimens 



have from 22 to 27 vertebrae preserved, all 



representing the distal half of the tail, and in 



most instances continuing to the tip. After a 



careful study of all these specimens, it appears 



that there are at least 45 vertebrae in the com- 

 plete caudal series of Stegosaurus, and in some 



individuals as many as 48 or 49 may be found. 



Marsh, in his restoration of Stegosaurus, shows 



the series as consisting of 46 vertebrae. 



The centra throughout the tail are short 



and remarkably uniform in length (see table of 



measurements, pp. 60 and 61) when compared 



with the caudal series of most other dinosaurs. 



The centra of the anterior half of the tail are 



broader than long, but these proportions are FlG . 26,-anteeioe caudal vertebra, probably 



reversed in the posterior half, where the verte- THE foubth, of stegosaurus ungulatus marsh. 



* . . , Cat. no. 0843, U.S.N.M. About J Nat. size. Side 



brae are more compressed transversely. All ol view, c, caudal rib or transverse process; s, 

 the caudals are constricted medially. S7mE < z - interior zygapophysis; z>, posterior 



J ZYGAPOPHYSIS. 



ihe caudal centra ol Stegosaurus may be 

 distinguished from those of other American Jurassic dinosaurs by their hexagonal 

 shape when viewed from the ends, as plainly indicated in figure 28. 



Fig. 25.— Second? caudal vertebra of Stego- 

 saurus UNGULATUS MABSH. £ NAT. SIZE. FRONT 



view", p, Transverse process; s, neural spine; 



2, ANTERIOR ZYGAPOPHYSIS. AFTER MARSH. 



