THE 



AMERICAN NATURALIST 



Vol. XLII June, 1908 No. 498 



THE ANCESTRY OF THE CAUDATE 

 AMPHIBIA 



DR. ROY L. MOODIE 



The phylogeny of the group of vertebrates commonly 

 called amphibians or batrachians has been, and still is to 

 some extent, among the most obscure of the problems con- 

 nected with the descent of animals. So far as I am aware 

 there have been but few statements as to the possible 

 ancestry of the Amphibia and no attempt has been made 

 to set forth in detail the series of structures through 

 which the animals have passed from the beginning of 

 their line to the present. During the course of an ex- 

 tensive investigation on the extinct Amphibia of North 

 America, the writer has reached some interesting con- 

 clusions in regard to the ancestry of at least one group of 

 the modern Amphibia and these conclusions are here set 

 forth in detail. Some of the facts offered in support of 

 these conclusions have been given in other connections. 



So far as at present known, the first trace of vertebrate 

 life on earth is that of fishes in Ordovician rocks in Colo- 

 rado and in two places in Wyoming, I e., the Black Hills 

 and the Big Horn Mountains. In the Devonian, if the 

 impressions from the Catskill are properly interpreted, 

 the fishes had given rise to a quadrupedal type of animals 

 which are usually known as the Amphibia. Only impres- 

 sions of footprints in the sandstone are known, but these 

 are cpiite instructive. There are no traces' of the bones 



