AN OLIGOCENE EAGLE FROM WYOMING 



By ALEXANDER WETMORE 

 Assistaiil Secretary, Siiiillisoiiian Iiistititlion 



Among the collections obtained by the paleontologic expedition con- 

 ducted in 1932 by C. W. Gilniore, curator of vertebrate paleontology, 

 United States National Museum, one of the most important s])ecimens 

 is a fossil eagle from Oligocene deposits in Niobrara County, Wyo. 

 This bird was discovered, in beds practically barren of other fossils, 

 by George F. Sternberg, who assisted Mr. Gilmore on the expedition. 

 Great care was used to secure all available fragments, and broken 

 bits have been skillfully fitted together in the laboratory by N. H. Boss, 

 so that the final specimen comprises most of the important elements of 

 the skeleton. The remains form the most complete representation 

 known of an individual bird from the Oligocene deposits of America, 

 and are of great importance in providing information on the early 

 development of the accipitrine group in North America. Description 

 of the specimen follows. 



Drawings illustrating the specimen are by Sydney Prentice. 



PALAEOPLANCUS STERNBERGI gen. et sp. nov. 



Characters. — Somewhat similar to Aquila and the larger species of 

 Biiteo, but metatarsus with projecting wing of second trochlea re- 

 duced, difl^ering in this respect from any of the related genera; skull 

 small ; premaxilla relatively slender with a pronounced festoon on 

 lower margin ; humerus and ulna relatively short and slender ; sternum 

 somewhat reduced ; f urcula with outer, free end greatly narrowed ; 

 liumerus with ectepicondylar process somewhat reduced ; pelvis rela- 

 tively large ; lower limb relatively strong ; trochanteric ridge of femur 

 considerably reduced ; feet with toes unusually large and strong. 



Type. — A partial skeleton, U.S.N.M. no. 12479, collected in the 

 Upper Oreodon beds of the Oligocene on the east side of Plum Creek, 

 Niobrara County, Wyo., on August 9, 1932. 



Description. — Skull (fig. i) with elongated, decurved, pointed tip, 

 premaxilla relatively slender ; narial aperture broadly open, somewhat 

 elongated ; ascending process of nasal fairly heavy ; quadrate heavy ; 

 mandible rather slender, with external articular process well developed 



Smithsonian Miscellaneous Collections. Vol. 87, No. 19 



