220 Lull — Development of Vertebrate Paleontology. 



and the mosasaurs and plesiosaurs of the Kansas chalk. 

 The last formation has also produced toothed birds, 

 Hesperornis and Ichtliyornis, which again are absolutely 

 unique. 



But it is in the mammalian class that the phylogenies 

 become so highly complete and of such great importance 

 as evolutionary evidences, for nowhere else than in our 

 own West have such series been found as the Dinocerata 

 and creodonts among archaic forms, the primitive 

 primates from the Eocene, the carnivores such as the 

 dogs and cats and mustellids, but especially the hoofed 

 orders such as the horses. Of these hoofed orders, the 

 classic American series of horses is complete, that of 

 the camels probably no less so, while much is known of 

 the .deer and oreodonts, the last showing several parallel 

 phyla, and of the proboscideans, which while having their 

 pristine home in the Old World nevertheless soon sought 

 the new where their remains are found from the Miocene 

 until their final and apparently very recent extinction. 

 These creatures show increase of bulk, perfection of feet 

 and teeth, development of various weapons, horns and 

 antlers, which may be studied in their relationship with 

 the other organs to make the evolving whole, or their 

 evolution may be traced as individual structures which 

 have their rise, culmination, and sometimes their senile 

 atrophy in a way comparable to that of the representa- 

 tives of the order as a whole. Thus, for example, 

 Osborn has traced the evolution of the molar teeth, and 

 Cope of the feet, while Marsh has shown that brain devel- 

 opment runs a similar course and that its degree of per- 

 fection within a group is a potent factor for survival. 



As a student of evolution, the paleontologist sees 

 things in a very different light from the zoologist. The 

 latter is concerned largely with matters of detail — with 

 the inheritance of color or of the minor and more super- 

 ficial characteristics of animals — and the period of 

 observation of such phenomena is of necessity brief 

 because of the mortality of the observer. Whereas the 

 paleontologist has a perspective which the other lacks, 

 since for him time means little in the terms of his own 

 life, and he can look into the past and see the great and 

 fundamental changes which evolution has wrought, the 

 rise of phyla, of classes, of orders, and he alone can see 

 the orderliness of the process and sense the majesty of 

 the laws which govern it. 



