Peaks of the Organ Mountains above the Centra de Primatologia; coastal plain in background. 



shape of the crowns of their molar teeth, are known 

 from fossils no more than about three million years old 

 but the actual time of their arrival in South America is 

 controversial. Some biogeographers say the mice came 

 from Central America when the connection with 

 South America was formed less than 3,000,000 years 

 ago. Others claim that the sigmodontine mice came 

 from Africa with the monkeys on the drifting con- 

 tinent. In any case, they are now the dominant mam- 

 mals of tropical America in numbers and kinds. Few of 

 them are well known, many others are believed to be 



Water rat (Nectomys squamipes) captured near the Centre. 



unknown to science. The Atlantic forest has a large 

 number of species peculiar to the region. More are be- 

 ing discovered as fruits of our work. 



Importance 



These small living descendants of the mammals of the 

 geologically oldest parts of South America must be stu- 

 died to learn where the Atlantic forest mammalian 

 fauna originated. Scientists also want to know how and 

 where they diversified and dispersed and their relation- 

 ship to living and extinct animals of other parts of the 

 world. They are also concerned with their present sta- 

 tus for survival; their interaction with man in some 

 ways known to be benign, in others harmful, but in 

 most ways still conjectured. 



The Experience 



About 150 small mammals represented by rodents, 

 marsupials, bats, and rabbits were collected in the 

 three-week period. Our field work terminated 15 

 November 1987. After 18 years of assisting Phil with 

 his research in the Museum, and typing his scientific 

 papers, field notes and diaries, 1 learned first hand what 

 field work was all about. None of this would have been 

 realized without the hospitality and cooperation of Dr 

 Coimbra-Filho, director of the Centro de Primatologia 

 do Rio de Janeiro, and his supporting staff. FM 21 



