Where to draw the nonprimate-primate taxonomic boundary

The known Cretaceous and Paleocene primates, the Paromomyiformes, although lacking a fully developed postorbital bar, are nevertheless, both cladistically and phenetically, closest to the common ancestor of the living primates. Not only their undisputed phylogenetic ties but also their early experiments inthe arboreal milieu necessitate their balanced evolutionary classification within the order Primates.