THE SMALLEST KNOWN HORNED DINOSAUR, 

 BRACHYCERATOPS. 



By Charles W. Gilmore, 

 Associate Curator, Division of Paleontology, United States National Museum,. 



The mounted skeleton of Brachyceratops montanensis recently 

 placed on exhibition (pis. 1 and 2) in the United States National 

 Museum is the smallest horned dinosaur that has yet been dis- 

 covered. It was found by the writer during the summer of 1913 

 in the Two Medicine formation of the Upper Cretaceous, while 

 working under the auspices of the United States Geological Survey 

 on the Blackfeet Indian Reservation, in northwestern Montana. 



Since the osteological details ^ of the skeletal structure have been 

 fully described, it is proposed here to give only a brief account of 

 the specimen as it is now prepared for exhibition. 



The mounted skeleton is 1625 mm. (5 feet, four inches) long 

 from the end of the beak to the tip of the tail, and stands about 

 762 mm. (30 inches) high at the hips, with a skull that measures 

 558 mm. (22 inches) in length. The skeleton is mounted standing on 

 a base of artificial matrix calculated to represent the color and texture 

 of the layer in which the bones were originally found. The animal 

 is posed in a quadrupedal walking position, the forelimbs strongly 

 flexed at the elbow, as indicated by the strong olecranon process 

 of the ulna. The tail drops rapidly from the sacrum and its distal 

 portion drags upon the ground. The scapula has been given a 

 horizontal position well down on the sides of the ribs, in accord- 

 ance with the evidence of the position of this bone in an articulated 

 skeleton of Monoclonius in the American Museum of Natural His- 

 tory, New York City. 



The painstaking care entailed in cleaning the bones of this skele- 

 ton from the adhering matrix, fitting together of the broken pieces, 

 the restoring of the missing parts, and the articulation and mounting 

 of the specimen can be more fully appreciated when it is explained 



1 Gilmore, Charles W., Smiths. Miscell. Coll.. vol. 63, No. 3, 1914,. pp. 1-10; Prof. 

 Paper 103, U. S. Geol. Survey, 1917, pp. 1-38, pis. 1-4, 47 text figures. 



No. 2424— Proceedings U. S. National Museum. Vol. 61, Art. 3. 



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