208 TEN years' progress in vertebrate paleontology 



CRETACEOUS DINOSAURS 



BY RICHARD SWANN LULL 



CONTENTS 



Page 



Introductory 208 



Theropoda 208 



Sauropoda - 209 



Orthopoda (Predentata) 210 



Ornithopoda, Iguanodontia 210 



Stegosauria 211 



Ceratopsia 211 



Conclusion 212 



Introductory 



As an anterior time limit I have taken the close of Morrison-Potomac 

 time in the New World and the Wealden, or its equivalent, in the Old, 

 my discussion covering the remainder of the dinosaurian career, whether 

 its final termination . were Mesozoic or, as the botanical evidence ad- 

 vanced by Knowlton would seem to indicate, actually in the Tertiary 

 period. The problem can best be discussed by taking the dinosaurian 

 suborders in the following sequence : 



Theropoda 



Previous to 1901 there had been described from the American Cre- 

 taceous a number of genera more or less incompletely known and prin- 

 cipally from beds of Senonian age, Judith Eiver and Belly Eiver. Of the 

 forms from the Danian, variously known as Ceratops, Laramie, Hell 

 Creek, or Lance formation, aside from several species of the compsog- 

 nathoid Ornithomimus, little was known, though the existence of an 

 immense type of the line of Allosaurus was more than suspected. In 

 1905 Osborn announced the discovery in the Hell Creek beds of two 

 new genera, Tyrannosaurus and Dynamosaurus. In 1906, in a second 

 contribution, Tyrannosaurus Avas much more fully described, while the 

 name Dynamosaurus was dropped as being separated from the former 

 genus on insufficient grounds. Aside from Tyrannosaurus, the name 

 Albertosaurus was given by Osborn to another "Cretaceous genus of 

 somewhat more primitive character . . . represented in the British 

 Columbia skulls hitherto described as Dryptosaurus." These skulls are 

 from the Edmonton series, which is considered by Barnum Brown to be 

 nearer an equivalent of the Belly River than of the Lance, possibly that 

 of the true Laramie. 



