The Amazon marmosets are poorly known and severely threatened – endemic to the arc of deforestation in southern Amazonia. Based on data from field expeditions across this global deforestation frontier, we provide new records and extend the range of Mico chrysoleucos, provide new records and refine the range of M. acariensis, report the first records of a species of Mico on permanently flooded forests, and hypothesize the existence of a hybrid zone of these two species and also M. melanurus.

The Djaffa Mountains guereza (Colobus guereza gallarum) is an endemic Ethiopian taxon. Information about its distribution and population size is missing. We collected data on population density and size in four forests in the Ahmar Mountains in a line-transect survey and estimated 109.6 individuals per square kilometer within the study area. This comparatively high density is thus not the main conservation concern, but the fragmentation of the guereza habitat and population is.