694 



COLLEGE ZOOLOGY 



^PLACENTALIA^ 



I MARSU PIALIA \ /MODERN BIRDS^ 



\MAMMALIA! / ; \ 



.\ MONOTREMATA/SERPENTES ,' TOOTHED BIRDS | 



' V ---V-" X \ I Avfes 



TESTUDINATA\ \ I 



s / ^ _ 



SALI ENTI^\! TESTU ~l N ATA 



THEROMORPHA 



FRdPTILIA 

 *HYNCHOCEPHALIA 



'ARCHAEOPTERYX/ 

 AMAT A 



CROCODILINI 



FIG. 551. Phylogenetic tree of vertebrates. Double underscoring in- 

 dicates an extinct group; single underscoring, those that have but a few 

 living representatives. The boundaries of the classes are represented by 

 dotted lines. (Modified after Wilder.) 



