122 



D. E. SAVAGE 



of the origin of these genera is shown in Table I. We may say that 

 the interval from Miocene into Pleistocene was the time when most 

 modern genera of land mammals arose. 



Most species in the living Nearctic land mammal fauna are evi- 

 dently autochthonous. Probable exceptions are the transboreal 



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PALEOCENE 



CRETACEOUS 



TIME OF ORIGIN OF LIVING 

 NEARCTIC MAMMALIAN FAMILIES 



Fig. 9. 



forms, such as the moose, muskox, caribou, and polar bear; certain 

 "pan -American" forms, such as Eptesicus juscus (big brown bat), 

 Lasiurus borealis (red bat), Tadarida macrotis (big freetail bat), and 

 Eumops perotis (Western mastiff bat); and probable Neotropical 

 autochthons — Dasypus novemcinctus (armadillo) and Tayassu angu- 

 latus (peccary). A species list of land mammals from the Pleistocene 

 [including the Holocene of some workers] is given by Hibbard 

 (1956; in Flint, 1957, pp. 458-467). No taxonomist will recognize 

 exactly the same number of species as appear on the compilation by 



