Various fossil primates have been found in South America and adjacent regions such as Panama and the Caribbean. Presently, 78 species of New World monkeys have been registered in South America. Around the middle of the Cenozoic, approximately 34 million years ago, two types of mammals appeared for the first time in South America: rodents and primates. Both of these groups had already been inhabiting other continents for millions of years and they simply arrived in South America rather than originated there. Analyses of evolutionary relationships have shown that their closest relatives were living in Africa at the time. Therefore, the most likely explanation is that they somehow crossed the Atlantic Ocean, which was less wide than today, landed in South America, and founded new populations
