A NEW SPECIES OF TROODONT DINOSAUR FROM THE 

 LANCE FORMATION OF WYOMING 



By Charles W. Gilmore 



Curator of Vertebrate Paleontology, United States National Museum 



INTRODUCTION 



The intensive search to which the Lance formation of Niobrara 

 County, Wyo., has been subjected by fossil-hunting expeditions 

 should seemingly have exhausted that jBeld so far as new dinosaurian 

 reptiles are concerned, especially the larger forms. It appears, 

 however, that the possibilities of a field are never fully exhausted, 

 as is attested by the recent discovery of an incomplete skull which 

 rivals Ankylosaurus in size and has the massive bony, domelike 

 enlargement of the skull, which is one of the striking characteristics 

 of the genus Troodon. The large size of the specimen as well as cer- 

 tain differences in skull structure at once distinguishes it from the 

 described species of this genus, all of which are from the geologically 

 more ancient Judith River and Belly River formations. The dis- 

 covery of more perfect material in the Lance may disclose characters 

 that will necessitate the -founding of a new genus, but for the present 

 I shall refer the specimen to the genus Troodon^ and propose the 

 name wyoTtiingensis to designate the species. 



The occurrence of Troodon in the Lance fauna was reported by 

 the late J. B. Hatcher ^ in 1905. In the article cited, under the 

 heading Troodon validtts, he says : " Teeth of a very similar size and 

 pattern are not uncommon in the Laramie [Lance] of Converse [now 

 Niobrara] County, Wyo." The discovery of the present specimen is 

 therefore in a way corroborative of Hatcher's observations of 25 

 years ago. 



Family TROODONTIDAE, 1924 

 Genus TROODON, 1856 



TROODON WYOMINGENSIS. new species 



Plates 1, 2, and 3 



Type. — U.S.N.M. No. 12031; consists of the upper posterior half 

 of the skiill, including the occipital region downward nearly to the 

 foramen magnum. 



^ Hatcher, J. B., U. S. Geol. Survey Bull. 257, p. 82, 1905. 



No. 2875.— Proceedings U. S. National Museum, Vol. 79, Art. 9. 



49238—31 I 



