116 D. E. SAVAGE 



(1 family) ; Insectivora (2 families) ; Primates (1 family) ; Chiroptera 

 (3 families); Edentata (1 family); Carnivora (5 families); Lago- 

 morpha (2 families) ; Rodentia (8 families) ; Artiodactyla (4 families). 

 However, 14 additional orders were here during various intervals of 

 the Mesozoic and Cenozoic, but are now either extinct or survive on 

 other continents: Multituberculata (extinct); Triconodonta (ex- 

 tinct) ; Docodonta (extinct) ; Pantotheria (extinct) ; Symmetrodonta 

 (extinct); Dermoptera (now in the Paleotropics) ; Tillodontia (ex- 

 tinct); Taeniodonta (extinct); Condylarthra (extinct); Notoungu- 

 lata (extinct); Pantodonta (extinct); Dinocerata (extinct); 

 Proboscidea (now in the Paleotropics) ; Perissodactyla (now in the 

 Paleotropics, Palearctica, and Neogaea). Of the 23 orders of land 

 mammals recorded in Nearctica, 9 have earliest record here, and 6 

 have earliest record here and elsewhere. First let us consider the 

 possibility that Nearctica was the origin and dispersal center for 

 these 15 orders, following the criteria proposed in the first part of 

 this paper; then we may consider the possible Nearctic origin for 

 other orders. Center of origin or origin area, as here used, of course 

 means place where earliest and most primitive members appeared. 



Orders with Earliest Record in North America 



1. Multituberculata (extinct) 



a. Earliest record in upper Jurassic of England and United States 



b. A group of uncertain phylogenetic affinities 



c. Possibly originated somewhere in Holarctica 



2. Marsupialia 



a. Earliest record in upper Cretaceous 



b. Comparisons on the basis of jaws and characters of dentition 

 lead to conclusion that this group was derived ultimately from 

 the Jurassic mammalian radicle, the Pantotheria; but forms with 

 annectant morphologies are unknown 



c. Possibly originated in North America, but comparable Cre- 

 taceous biocenoses are poorly known in Asia and are not yet 

 known on the other continents 



3. Dermoptera ("flying lemurs") 



a. Earliest record in upper Paleocene 



b. Probably distinct since middle or early Paleocene derivation 

 from generalized unguiculate eutherian; intra-ordinal relation- 

 ships are uncertain 



c. Possibly originated in North America, but poorly known in the 

 North American fossil record and unknown as fossils elsewhere 



