DINOSAUR QUESTION 1 7 



In regard to the discussion as to whether Dinosaurs 

 were contemporaneous in South America with the fauna 

 of the Deseado, I can only say. we found no trace of a din- 

 osaur or any other Cretaceous animal in the Deseado beds 

 which we worked. As the Cretaceous beds lie as high as 

 the Deseado and are also practically horizontally striated, 

 dinosaur remains might be found on the same level. I 

 think the assigning of any such material to these beds was 

 due to failing to recognize the unconformity under the 

 Deseado beds. As to the Xotostylops fauna and dinosaurs 

 being contemporaneous, I only worked the Xotostylops 

 beds at Mazaredo. but there I found nothing to indicate 

 the contemporaneousness of these two groups. As I have 

 shown above, Ameghino's idea of the extent of the Xoto- 

 stylops or Casamayor beds was mostly at fault, and very 

 much of that which he has designated as of Xotostylops 

 age is Upper Cretaceous. It is in these Upper Cretaceous 

 beds that dinosaurs do occur and this seems to me to be the 

 basis of the confusion. 



This Upper Cretaceous series is a field where consider- 

 able work may profitably be done, in straightening out 

 the relationships of the various layers to each other, their 

 extent, and their relationship to the Salamanca and other 

 Upper Cretaceous formations in other parts of Argentine. 



As to the age of the Deseado deposit which we worked. 

 It is under the Patagonian, and therefore must be as old as 

 the Oligocene. On the other hand it must be as young 

 as the Eocene, lying as it does above the Upper Cretaceous. 

 Of the three general faunas described it is clearly more ad- 

 vanced than either the Casamayor, or the Astraponotus; 

 so should be put as the youngest of these three. The 

 Colpodon, the Astrapothericulus and the Xotohippus, 

 faunas are said to be interstratified with the Patagonian 

 and therefore of the same age. The amount of advance- 

 ment from the Casamayor to the Deseado is considerable 

 and the relationships of the Deseado are fairly close with 



