Abstract
The genus Trogloderus LeConte, 1879, which is restricted to dunes and sandy habitats in the western United States, is revised using morphological and molecular information. Six new species are described from desert regions: Trogloderus arcanus New Species (Lahontan Trough); Trogloderus kandai New Species (Owens Valley); Trogloderus major New Species (Mohave Desert); Trogloderus skillmani New Species (eastern Great Basin and Mohave Desert); Trogloderus verpus New Species (eastern Colorado Plateau); and Trogloderus warneri New Species (western Colorado Plateau). A molecular phylogeny is presented for the genus and used to infer its historical biogeography. The most recent common ancestor of Trogloderus is dated to 5.2 mya and is inferred to have inhabited the Colorado Plateau. Current species most likely arose during the mid-Pleistocene where the geographic features of the Lahontan Trough, Bouse Embayment and Kaibab Plateau were significant factors driving speciation.