A new monotypic genus, Oncaglossum Sutorý, endemic to central Mexico, is described based on Cynoglossum pringlei Greenm. from the state of Mexico and belongs within the tribe Cynoglosseae of the Boraginaceae. The new genus is related to Cynoglossum L. subg. Eleutherostylum (Brand) Riedl and can be distinguished from the North American species currently classified in Cynoglossum by its calyx with imbricate, colored, and broadly ovate sepals, the corolla lobes reduced to narrow strips, anthers on short filaments inserted on the corolla margin, the stigma in the form of a lenticular disc, and tricolporate pollen grains with an additional aperture in their polar region.