58 



BULLETIN 89, UNITJBD STATES NATIONAL MUSEUM. 



Caudal vertebrae. — Tn the palooiitological colloction of the National Museum 

 thero are no less tliaii 7 articulated scries 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 I'egion of Stegosaurus. 



With specimen No. 4934 there are 22 cau- 

 dals preserved, 17 being articulated with the 

 sacrum. The romaiiiing 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 



Fig. 25.— SECON])? CAUIIAI, VERTlCliUA ui' Steuo- 1 ' "' 



sAUEus VNOiiLATUS Marsh. Jnat.size. Fkont an equal 

 VIEW. ;), Tkansveese PBOCEss; .s', NEUKAL spine; ,1 ,, ,yi ], f, •,. 



2, ANTERIOR ZYOAPOPHYSIS. APTER MAKSIL H UOX 



from the 

 distal end of the series. Tlie oth(>r specimens 

 have from 22 to 27 vert(*brae preserved, all 

 representing the distal half of tlie tail, ai\d in 

 most instances coutiivuing to the tip. After a 

 careful study of sdl tliese specimens, it app(>ars 

 that there are at least 45 vertebrae in the com- 

 plete caudal series of Stegosaurus, and in some 

 indi'vaduals as many as 48 or 49 may bo 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 o1' the anterior half of the tail are 

 broader than long, but these proportions are v 

 revelled in the posterior half, wliere the verte- 

 brae are more compressed transversely. .i\ll of 

 the caudals are constricted medially. 



The caudal centra of Stegosaurus may be 

 distinguished from those of other American Jurassic dinosaui'S by their hexagonal 

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



la. 2(5.— .\NTEKIOR CAUDAL VERTEBRA, PROBABLY 

 THE POURTIl, 07 STEGOSAURUS UNGULATUS MARSH. 



Cat. no. Ol)40, U.S.N.M. About \ nat. size. Side 

 viKW. c. Caudal kik or transverse process; s, 

 simne; j, anterior zygapophysis; z', posterior 



ZYG apophysis. 



