Two new species and a new record for Onosma L. (Boraginaceae) from northwestern Iran

Onosma atrii and O. persica are described and illustrated as new species and O. caucasica Levin is recorded for the first time from northwestern Iran. The two new species are placed in subsect. Asterotricha (Boiss.) Gürke, because of the asterotrichous indumentum (stellate trichomes) of their basal leaves. An extensive review of the literature and comparison with specimens from various European and Asiatic herbaria led to the recognition of these novelties. Our argument for these innovations is based on observation of significant differences in taxonomically important morphological characters including trichome type, shape and size of basal and cauline leaves, shape and size of calyx and corolla, annulus hairs, anther length, connection type and degree of exsertion, and nutlet morphology. The diagnostic morphological characters of closely related species are discussed, and for each new species a detailed description and details of distribution and conservation status are provided. An updated synoptical key to the species known from the Flora Iranica region and Atropatene sub-province is provided.