LIFE OF TERTIARY PERIOD 241 



As it has been found in various parts of the continent, it was 

 probably abundant. Another smaller animal of somewhat 

 similar form was the Nototherium, which was found in Queens- 

 land, together with the Diprotodon, about fifty years ago. 

 A large phalanger was also found, which Professor Owen 

 called the pouched lion {Thylacoleo carnifex), but it is doubtful 

 whether it was carnivorous (see Fig. 93). True carnivorous 

 marsupials allied to the " Tasmanian wolf" (Thylacinus) and 

 the Tasmanian devil {Sarcophilus) are also found. 



How and when the marsupials first entered Australia 

 has always been a puzzle to biologists, because the only non- 

 Australian family, the opossums, are not closely allied to 

 any of the Australian forms, and it is the opossums only 

 which have been found in the European Early Tertiaries. 

 But recent discoveries in South America have at length 

 thrown some light on the question, since the Santa Cruz beds 

 of Patagonia (Middle Tertiary) have produced several animals 

 whose teeth so closely resemble those of the Tasmanian 

 Thylacinus that Mr. Lydekker has no doubt about their being 

 true marsupials allied to the Dasyuridae. There is also, in the 

 same beds, another distinct family of small mammals — the 

 Microbiotheridae of Dr. Ameghino — which, from a careful 

 study of their dentition, are also considered by Mr. Lydekker 

 to be " polyprotodont marsupials of an Australian type." l 



But even more important is the discovery of living 

 marsupials of the Australian rather than the American 

 type in the very heart of the South American fauna. In 

 1863 a small mouse-like animal of doubtful affinities was 

 captured in Ecuador. But in 1895 a larger species of the 

 same genus was obtained from Bogota ; and it was then 

 seen that they belonged to a group of which large numbers 

 of fossil remains had been found in the Santa Cruz beds. 

 By a comparison of these remains of various allied forms 

 with the specimens of those now living, it seems no longer 

 possible to doubt that marsupials of Australian type have 

 existed in South America in Middle or Late Tertiary times, 

 and that some of them survive to-day in the equatorial 

 Andes, where their small size has probably saved them from 

 extinction. Of these latter, Mr. Lydekker says : " In the 



1 A Geographical History of Mammals, p. 109. 



R 



