34 



tTNITED STATES NATIONAL MUSEUM BULLETIN 294 



An incipient development of the median longitudinal 

 keel is observable on the ventral surface of the centrum 

 of the first lumbar and on the eleventh and twelfth this 

 keel is low, rounded, and not prominent. The neural 

 spines decrease in height from first to last and presum- 

 ably were as wide on those missing between the first and 

 eleventh as on the latter. Large elongated and laterally 

 compressed metapophyses were developed on the lum- 

 bars. The neural canal diminished in height from the 

 first to the last lumbar. The configuration of the trans- 

 \-erse process w;is altered from the elongated and rela- 

 tive narrow process of the first lumbar to the broad 

 subspatulate form on the last lumbar and the length 

 reduced about one third. See table 21 for measurements 

 of the lumbar vertebrae. 



First lumbar. — This vertebra was found in normal 

 sequential contact with the hindermost vertebra in the 

 consecutive series of twelve dorsal vertebrae. Thus there 

 can be no doubt as to its position in the vertebral series. 

 It was damaged when found and a narrow gap exists 

 between the upper portions of the pedicles of the neural 

 arcli and tlieir bases. The right metapophysis was de- 

 tuclied and the left transverse process was missing. The 

 ]nost obvious alteration in this first lumbar is the back- 

 ward inclination of the neural spine (pi. 1!), fig. 8) which 

 rises 212 mm. above the roof of the neural canal and 

 is horizontally tnmcated distally. The anterior border 

 of the neural spine is, however, eroded; its extremity 

 may possibly have been slightly expanded. The back- 



Table 21. — Measurements {in mm.) of the lumbar vertebrae, 

 USNM 83636 



Anteroposterior diameter of centrum 



Transverse diameter of centrum, ante- 

 riorlj- 



Vertical diameter of centrum, anteriorly 



Minimum anteroposterior lengtli of 

 ])ediclo of neural arch 



Transverse diameter of neural canal, 

 anteriorlj- 



\'ertical diameter of neural canal, 

 anteriorly 



Distance between ends of transverse 

 processes 



Dorsal edge of metapophysis to ventral 

 face of centrum, anteriorly 



Tip of neural spine to ventral face of 

 centrum, posteriorly 



Transverse diameter of centrum, pos- 

 teriorly 



Vertical diameter of centrum, poste- 

 riorly 



ward projecting portion of the neural arch extended 

 beyond the level of the posterior face of the centrum. 



The centrum is approximately the same length (110 

 mm.) as that of the twelfth dorsal and the contour of the 

 anterior end (pi. 21, fig. 5) is quite similar. The lateral 

 and ventral surfaces of the centrum are deeply concave. 

 No distinct median longitudinal ventral keel is devel- 

 oped on the centrum and no visible longitudinal ridge 

 is discernible on tlie depressed floor of the neural canal. 



The dorsoventrally compressed transverse process, 

 which projects outward from the external face of the 

 centrum at essentially the same level as that of the 

 twelfth dorsal, is constricted near the base, widened be- 

 yond the middle of its length, and then the anterior 

 border is obliquely truncated toward its narrowed ex- 

 tremity. It exhibits a tongue-like enlargement on its 

 anterior border. Tlie left transverse process is essentially 

 complet excejjt for the outer edge. 



The base of each thin (compressed from side to side) 

 pedicle of the neural arch occupies approximately two- 

 thirds of the length of the dorsal face of the centrum. 

 They support the large metapophyses which rise at least 

 60 mm. above the dorsal rim of the anterior epiphysis 

 and are separated anteriorly by a gap of 37 mm. ; they 

 also extend well beyond the level of the anterior face of 

 the centrum. The metapophyses are compressed from 

 side to side and project upward and forward from the 

 neural arch beyond the level of the anterior face of the 

 centrum. Neither pre- nor post-zygapophysial facets are 

 present. Tlie transverse diameter (35 mm.) of the neural 

 canal anteriorly is approximately equivalent to that of 

 the twelfth dorsal. 



Eleventh lumbar. — This lumbar was found immedi- 

 ately preceding the twelfth lumbar which was itself in 

 contact with the first caudal, when this portion of the 

 skeleton was excavated. The outer half of the right 

 dorsoventrally compressed transverse process was miss- 

 ing, but the left process (pi. 22, fig. 3) is sufficiently com- 

 plete to indicate the original shape. This process projects 

 outward almost horizontally and is inclined slightly 

 forward; its distal half is widened anteroposteriorly. 

 The broad (minimum width, 96 mm.) neural spine (pi. 

 22, fig. 1) rises 170 nun. above the roof of the neural 

 canal and is tnmcated distally. The backward projecting 

 dorsal portion of the neural arch extends beyond the 

 level of the i)osterior face of the centnun. 



Tlie base of each pedicle of the neural arch occupies 

 about four-sevenths of the length of the dorsal face of 

 the centnun. These thin pedicles support the large side- 

 to-side compressed metapophyses which rise 63 mm. 

 above the dorsal rim of the anterior epiphyses, and 

 barely project forward beyond the level of the anterior 



