OSTEOLOGY OF THE CARNIVOROUS DINOSAURIA IN THE UNITED 

 STATES NATIONAL MUSEUM, WITH SPECIAL REFERENCE TO THE 

 GENERA ANTRODEMUS (ALLOSAURUS) AND CERATOSAURUS. 



By Charles Whitney Gilmore, 



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



INTRODUCTION. 



In the present paper it is proposed to discuss all of the Theropodous dinosaur 

 specimens contained in the collections of the United States National Museum. 

 The material at hand includes the remains of many individuals, several of which 

 are represented by a considerable part of the skeleton; there are also quite a large 

 number of separate bones. Of the associated skeletons the type of Oeratosaurus 

 nasicornis Marsh is worthy of special mention, for it comprises parts of almost the 

 entire skeleton, and was to a considerable extent found articulated. Although 

 this specimen was found more than 30 years ago it is still the most perfect example 

 of the genus yet discovered. A specimen of Antrodemus Leidy originally described 

 and figured as Allosaurus fragilis consisting of the skull and lower jaws, presacral 

 vertebrae, complete sacrum, and 30 or more caudal vertebrae, pelvis, ribs, and all 

 four limbs and feet, is of interest as being the individual of which Marsh published 

 illustrations of the articulated hind limb and pelvis (as fig. 2, pi. 11), in Dinosaurs 

 of North America. A second specimen, No. 8367, U.S.N.M., may also be mentioned 

 not only on account of there being a considerable part of the skeleton but also 

 because of the remarkably fine state of preservation of the bones. 



The considerable number of type specimens, even though many are fragmentary, 

 add much to the importance of this collection of carnivorous dinosaur remains in 

 the United States National Museum. These are: Oeratosaurus nasicornis Marsh, 

 Allosaurus medius Marsh, Laorosaurus ferox Marsh, Antrodemus valens Leidy, 

 Creosaurus potens Lull, Coelurus gracilis Marsh, Ornithomimus sedens Marsh, and 

 0. tenuis Marsh. The type specimens of Ornithomimus minutus Marsh and 0. 

 grandis Marsh should be in these collections, but I have been unable to positively 

 identify them. Several of these types have been only too briefly described, and a 

 number of them have never been figured. All of these are here illustrated, rede- 

 scribed, and the information concerning them brought up to date. This procedure 

 it is hoped will make them more fully available to future students of the Theropoda. 



One of the interesting discoveries resulting from this work was the recognition 

 of an Ornithomimid dinosaur among the materials from the Arundel formation of 

 Maryland, here made the type of the new species Ornithomimus affinis. It records 

 the first occurrence of a member of this family east of the Mississippi River, and also 

 its first occurrence in a formation older than Upper Cretaceous. 



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