Abstract
It has been confirmated the existence of at least 25 localities with the rests of fossil megamammals. In Bajo Barrantes (San Ramón) an assocíation of Villafranchian (?) fauna of south american origen was found. It is represented of Toxodon aff. platensis, megatherium and nylodons. It was also verified during quaternary different species of proboscideans like Mammuthu aff. imperator, Cuvernius hyodon and other mammals among them, Equus sp., stroll in this part of Central America. Mammuthus aff. -imperator shows che major geographical distribution known in northern part of the continent. If the finding of bisons in Nicaragua ís taken in consideration ic is concluded that the region between Southern Nicaragua and Central Costa Rica, has the maximum extensior of some species of big mammals; diverse geographycal barriers could have retarded their migratioa. Coexistence with man at the beggining of Holoceno could be an aditional factor helping to extintion. The rest of verrebrates found stratigraphycally between or under ignimbrites, do have few possibilities to be associated rests or numan tools while finalr. in volcanic or Holoceno sediments presenr híg probabilities of coexistence with man.