THE PHYLOGENY AND CLASSIFICATION OF 

 REPTILES 



S. W. WILLISTON 



University of Chicago 



Not many years ago it was the fashion to construct phylogenetic 

 trees, often of wonderful design, for almost every group of animal 

 and vegetable life. Because of the failure of so many of them, the 

 practice has somewhat fallen into desuetude in recent years, and 

 it is only hesitatingly that I have ventured, for the first time, to 

 express in tabular form my own views of the phylogeny and classi- 

 fication of the reptiles. I do so the more readily, however, as I 

 have no startling novelties to offer. 



Phylogenetic schemes are always useful when constructed with 

 proper discrimination and with due regard to the known and the 

 unknown. They often furnish some residue of permanent knowl- 

 edge, some real contribution to taxonomy and the doctrine of 

 evolution; or, if not, by their failure they limit the field of legiti- 

 mate speculation. 



Especially has our greatly increased knowledge of the early 

 land vertebrates, both at home and abroad, rendered it possible, 

 I believe, to approximate more closely the real origin of many 

 forms of vertebrate life than it was a dozen years ago. It was not 

 long ago that we were seeking the beginning, or at least the early 

 stages, of all reptile life in the order Rhynchocephalia. Because 

 we found, or thought that we found, in Sphenodon, or Hatteria, as 

 the genus was long called, the most generalized or primitive char- 

 acters among living reptiles, it was not unnaturally assumed that 

 its immediate ancestral stock was the most primitive reptilian 

 type of the past. And when Credner discovered a quarter of a 

 century ago, far back in the Permian rocks, another very primitive 

 reptile, it was also assumed, too readily, that it was of the same 

 stock. Upon that error, and it was an error, was built an elaborate 

 edifice with the Rhynchocephalia as its cornerstone, until, as so 



411 



