Comparisons of species composition in prehistoric (8.0 x 10(3) to 1.2
x 10(3) years ago) and contemporary assemblages of caviomorphs from ce
ntral Chile reveal that species richness has decreased through the Hol
ocene. The local extinction of two species, Aconaemys fuscus and Octod
on bridgesi, suggests that current assemblages are impoverished and ne
sted subsets of prehistoric caviomorph assemblages.