The oldest known anthropoid postcranial fossils and the early evolution of higher primates

The middle Eocene primate family Eosimiidae, which is known from sites in central and eastern China and Myanmar, is central to efforts to reconstruct the origin and early evolution of anthropoid or 'higher' primates (monkeys, apes and humans). Previous knowledge of eosimiid anatomy has been restricted to the dentition and an isolated petrosal bone, and this limited anatomical information has led to conflicting interpretations of early anthropoid phylogeny. Here we describe foot bones of Eosimias from the same middle Eocene sites in China that yield abundant dental remains of this primate. Tarsals of Eosimias show derived anatomical traits that are otherwise restricted to living and fossil anthropoids. These new fossils substantiate the anthropoid status of Eosimias and clarify the phylogenetic position of anthropoids with respect to other major primate clades. Early anthropoids possessed a mosaic of primitive and derived traits in their postcranial skeletons, reflecting their derivation from haplorhine ancestors that retained many prosimian-like features.