PROCEEDINGS OF THE UNITED STATES NATIONAL MUSEUM 



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SMITHSONIAN INSTITUTION 



\J. S. NATIONAL MUSEUM 



Vol. 84 V/ashingtcn : 1937 No. 3023 



ON THE DETAILED SKULL STRUCTURE OF A CRESTED 



HADROSAURIAN DINOSAUR 



By Ceaeles W. Gilmore 



Curator, Division of Verieh'raie Po'leordology, United Stales N^ational Museum 



A PARTIAL skeleton of a crested hadrosaurian dinosaur, collected 

 by the Smithsonian PaiecLtological Expedition of 1928, is unique in 

 having the occipital region of the skuU disarticulated, thus displaying 

 structural features not before observed in the Hadrosauridae. The 

 specimen (U.S.N.M. no. 11893) comes from the Two Medicine 

 formation of the Upper Cretaceoas and was found by G. F. Sternberg 

 on the north side of the Two Medicine River, Blackfeet Indian 

 Reservation, Teton County, Mont. Although a considerable part 

 of the skeleton was recovered, it is only the skull parts with which 

 we are now concerned. 



That this specimen pertains to the subfamily Lambeosaurinae is 

 clearly indicated by the red-uced number of vertical rows of teeth in 

 the dentaries, the deep and nearly vertical suture between the frontal 

 and nasal bones for the better anchorage of the crest, and the short, 

 broad nature of the cerebral expansion of the brain as indicated by the 

 frontal contribution to the brain case. 



The lack of the crest portion of the skull and the juvenile character 

 of the present individual make it very difficult if not impossible to 

 identify tliis specimen generically at this time. 



The detailed osteological structure of the occipital segment is the 

 least-known part of the hadrosaurian skull, for in most crania the 

 sutures are coalesced, thus obscuring or hiding entirely the precise 

 extent of the individual elements. 



8838—37 481 



