Abstract

Fossil records for basal New World skunks (subfamily Mephitinae) have been slowly but steadily increasing in recent years. Fossils for both living and extinct genera are now dense enough that actual evolutionary steps leading to living clades are beginning to be resolvable. We document a new species of the extinct, transitional genera Buisnictis, B. metabatos sp. nov., from Early Pliocene San José del Cabo Basin, Baja California Sur, México. B. metabatos possesses a combination of primitive and derived features, including a broadened P4 protocone shelf, a notch anterior to the m1 entoconid, and relatively unexpanded M1 lingual cingulum. It thus fills in yet another morphological gap and it is at a basal position within or just outside of the living skunk clade. Although current records are still far too scattered to resolve detailed zoogeographical patterns, we are in a position to speculate that since the Early Pliocene, southern North America and Central America have acted as a refugium for skunks. As a basal skunk, Buisnictis metabatos probably gave rise to the modern crown clade. There is evidence to suggest that both spotted skunks (Spilogale) and hog-nosed skunks (Conepatus) had their centres of diversification in Mexico or Central America. The only exception may be the striped and hooded skunks (Mephitis), which have a more northerly distribution.