PROF. OSBORN ON THE ORIGIN OF MAMMALS. 



415 



THE ORIGIN OF MAMMALS. 



Since the Source of the Mammalian phylum was later than that 

 of the Reptilian phylum in the Permian and possibly Carboniferous, 

 we are sure that it extended at least very far back into the Triassic, 

 and the Triassic was apparently a time of great continental con- 

 nections and of consequent wide geographical distribution even of 

 land types. But in presenting a phylogenetic chart which traces 

 the origin of Mammals to the Upper Permian, I am quite as 

 conscious as the most conservative zoologist present that we are 

 not on sure ground, that this is a castle of cards liable to fall at 

 any moment. Yet such a chart, involving as it does numberless 

 hypotheses, is necessary to set forth certain ideas, 



HYPOTHETICAL PHYLOCENYof theMANIMAUA 



ASDCfilV£D FROM PALJCONTOLOCY/8B8 

 REC£NT INSECTIVOM . . * MONOTREMATA 



TERTIARY 



CRETAC. 



JURAS. 



TRIAS. 



Carb. 



:i«KPP 



RODENTIA 

 TILLODONTIA 

 CANODOiffA 

 EDENTATA 



TPRii^SJcoNDYLARTHRV 

 \ t /"[AMBLY PODA 



CREODONTA 



TRJCONODONTA 



Placentalia Marsupiaua 



ML 



THLAlODOli 



vltituberculata 



' (&ARNrvoRousJC"77/vsrcnw)fibi/SKj " '(H€RBivdkousj"' 



IDKYHODOHTIA Z,THEhlODOHTIA \HfKTH€RlA I .C0HPHODOKTA 



(PROCMnSAURIK- 



^ROMAmtHAUA 



KRM.^XRHfHCHOCEPHAUA C UfJOMODONTIA 



(MONOCONDYLIA) (MOHO.&^D/COAIDYLIfi) 



iJCOTYLOSAURIA= AMPHIBIAX 

 ^{PARIASAURlA IDICONDYLIA)] 



\ REPTIUA 



STtCOCEPHALA- LABYRIHTh] 

 (OICONDYLIA) 



Clearing the way for this discussion, this chart first sets aside 

 the general view defended by Huxley in 1880, of a genetic suc- 

 cession between three sub-classes of mammals, which has become 

 a matter of creed with many zoologists. In the last eighteen years 

 not a scintilla of evidence has arisen to show that Placentals are 

 descended from Marsupials, and of late, evidence has been coming in 



