MATTHEW, CLIMATE AND EVOLUTION 



363 



The fragmentary and little known mammals from the Mesozoic for- 

 mations of Europe and North America were in large part marsupials, so 

 far as we can judge from what is known of them. 



The most distinctive group among them were Multituberculata or 

 Allotheria. Gidley^'* has recently (1909) brought forward strong evi- 

 dence for the view that these animals were an archaic, early specialized 

 branch of the marsupials paralleling the later diprotodonts.'^^ They 

 occur (doubtfully) in the Ehsetic of Germany, certainly in the Upper 



Tertiary 

 Opossums 

 BorhifOiniiis 

 Caenolestiais 



Opossums pro^ai/u 

 since Creta. 



ThylcLCi'nus 

 ustralca in 

 :^v Pleistocene) 



W/,0, 



ipos 



sums 



Cdenolestcs \S^\\\ X)asi/ures;Diprofodo?-ttia. 



Fig. 31. — Distribntiou of Marsupials 



This is probably to be regarded as due to a very ancient dispersal from the north, fol- 

 lowed by differentiation and dispersal during the Tertiary of specialized adaptations 

 parallel in the Neotropical (Borhysenids and Csenolestids) and Australian regions (Thy- 

 lacine-Dasyures and Diprotodonta). The Phalangers of the Austromalayan islands are 

 regarded as marginal types from an Australian dispersal center. 



'*J. W. Gidley: Proc. U. S. Nat. Mus., vol. xxxvi, pp. 611-626. 1909. 



''^ Recent discoveries, made since these lines were written, indicate that the relationship 

 was not as close as had appeared. Dr. Broom has even maintained that these animals 

 were nearer to monotremes than to marsupials, but in my judgment he has failed to 

 adduce any really valid evidence for this view. But while they are in the Metatherian 

 stage of evolution I do not think they can be included in the order Marsupialia on the 

 data now available. See forthcoming article by Walter Granger in Bulletin Am. Mus. 

 Nat. Hist. 



