Mazus unguiculatus (Mazaceae), a distinct new species from Anhui Province, eastern China.

Mazus unguiculatus Bo Li, a new species of Mazaceae from Anhui Province in eastern China, is described and illustrated. Phylogenetic analyses based on combined chloroplast DNA regions (matK, rbcL, rps16, and trnL-F) and the nuclear ribosomal internal transcribed spacer (nrITS), together with morphological evidence, confirm that the new species is sister to M. spicatus Vaniot. It is distinguished from the latter and all other congeners by its unique corolla morphology, viz., the upper lip is bilobed, each lobe has an emarginate to bilobed apex, whereas the lower lip is deeply trilobed with subequal lobes; each lobe possesses a short claw at the base and shallow teeth at the middle of the apex, and the palate is absent. A detailed description is provided, along with information on its distribution, habitat, and conservation status.