Global trends and biases in new mammal species discoveries.

Contrary to common perception, the number of living mammal species and the relationship of those species with one another are incompletely understood. Taxonomic revisions within mammals are frequent and are often motivated by the discovery of new species. In fact, an analysis of patterns of discovery suggests that complete alpha-taxonomic characterization of living mammals remains a far-off goal. Examination of chronological, geographical, and taxonomic trends in new species discoveries reveals interesting trends, telling biases, and priorities for further study. An average of 223 new valid species have been described per decade since the birth of modern taxonomic nomenclature in 1758, and this rate is increasing. Over 300 new mammal species are expected to be described this decade and some estimates suggest that 7,000+ living species of mammals will eventually be recognized. An analysis of 341 recently described species indicates that the great majority of them are restricted to threatened areas of high endemism—reiterating the biotic richness of these regions, but also indicating that most new species and the regions in which they occur require urgent conservation attention. That the global mammal fauna remains so incompletely characterized reflects the woeful state of knowledge of global biodiversity.