We agree with Frank Zachos and colleagues that splitting mammalian species taxonomically without scientific justification could impede their conservation (Nature 494, 35; 2013). But so does uncritically lumping them together.

Mammalogy is beleaguered by a dogmatic regard for mid-twentieth-century propositions, which were seldom based on critical study and lacked phylogenetic information. Species were lumped together and incorporated into influential classification checklists to simplify regional faunas and make them more manageable for non-taxonomists.

Modern integrative approaches have shown that this tactic has hidden an incommensurable number of distinctive species from conservation efforts (W. R. Morrison et al. Biol. Conserv. 142, 3201–3206; 2009), thereby increasing the risk of extinctions.

Scepticism should be accorded to any taxonomy that is not based on comprehensive revisionary work, phylogenetic studies or, ideally, both.