2 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. ']2 



ALAMOSAURUS SANJUANENSIS, new species 



Plates I, 2 



Type. — Cat. No. 10,486, U. S. N. M., consists of the nearly com- 

 plete left scapula. 



Paratypc. — Cat. No. 10,487, U. S. N. M., consists of the nearly 

 complete right ischium. 



Type locality. — Barrel Spring Arroyo, one mile south of Ojo 

 Alamo, San Juan County, New Mexico. 



Horizon. — Ojo Alamo formation, Upper Cretaceous. 



Collector. — J. B. Reeside, Jr., June, 1921. 



The scapula and ischium designated as the type and paratype, 

 respectively, were found in the same geological horizon, but some 

 200 feet distant from one another. While it is quite possible that 

 both may pertain to the same individual, it is thought best to regard 

 them as distinct until their closer relationship can be more positively 

 established. 



Scapula. — The scapula is in a good state of preservation except for 

 the loss of a portion of the proximal or articular end (see pi. i) 

 where it projected above the ground and was weathered away. The 

 suprascapular end is also incomplete, though apparently only the 

 border is missing. In size this bone rivals the largest of the Camara- 

 saurus scapulae described by Messrs. Osborn and Mook,^ since as 

 preserved its greatest length is 155 cm. (60 inches), and it is con- 

 servatively estimated that the total length of the complete bone would 

 have been at least 170 cm. (68 inches). 



In outline, as shown in plate i, the blade of the scapula dififers from 

 any described form in that there is a gradual widening of the shaft 

 from below upward to the superior end, there being no especial expan- 

 sion of the anterior border as found in Camarasaurus, nor rapid 

 superior expansion of both borders as found in Diplodocus and 

 Haplocanthosauriis. While this portion of the bone is heavy it is not 

 so massive as in Camarasaurus, being much thinner. The superior 

 end is flattened out, though the external surface becomes convex trans- 

 versely as the middle of the bone is approached. From end to end 

 the bone is curved as in other members of the Sauropoda. Both 

 anterior and posterior borders thin out to sharp edges, this condition 

 continuing downward half its total length. Immediately above the 

 point where the anterior border begins to turn upward to form the 

 prescapular expansion of the lower end the border becomes thick- 



* Memoirs Amer. Mus. Nat. Hist., new sen, vol. 3, pt. 3, 1921, p. 3^1, fig. 74. 



