Some burrowing mammals have been considered ecosystem engineers since they build potential microhabitats for vertebrates and invertebrates. Thus, these species may function as keystone species in their communities, because they may be beneficial to several other species. In this study we tested the possible influence of the burrow density of Clyomys bishopi and armadillos (Cabassous unicinctus and Euphractus sexcinctus) on the diversity (richness) of terrestrial vertebrates (frogs, lizards and small mammals) in a savanna (Cerrado) area in southeastern Brazil. Ten areas of grassland with scattered shrubs (“campo sujo”) were sampled from August 2007 to January 2008 at Itirapina Ecological Station. In general, the burrow density seems to have a positive effect on the richness of terrestrial vertebrates (frogs, lizards and small mammals). However, armadillos are apparently the most important burrowers in this ecosystem, because they, unlike Clyomys bishopi, dig burrows not only for sheltering, but also for feeding, thereby increasing the probability of their use by other species. These results support the hypothesis that these burrowing mammals may function as possible ecosystem engineers or keystone species in this community.