Acantholimon riyatguelii (Plumbaginaceae), a threatened new unarmed species from Central Anatolia, Turkey

Acantholimon riyatguelii is described as a new species. Diagnostic morphological characters, a full description and detailed illustrations are provided on the basis of the type specimen and wild exemplars. This outstanding new species is a strict gypsophyte, which is characterized by the dwarf caespitose perennial habit, not forming dense thorny cushions; leaves are homomorphic, hairy, short and quite soft, not pungent but mucronate, swollen-fleshy and calcareous-punctate; spikes are unbranched, very compact, distichous, longer than leaves; spikelets are numerous and quite regularly imbricate; and the calyx is 5-lobed, with whitish limb. These combination of morphological characters in not known in any other Turkish Acantholimon species, and allows easy identification. The main morphological traits of A. riyatguelii suggest inclusion in A. sect. Staticopsis, though in an isolated position for which a new subsection, A. subsect. Exacantha, is described. Morphological affinities and divergences to other members of that section are dicussed. Furthermore, data are reported on the conservation status of A. riyatguelii, which is suggested to be labelled as CR according to the IUCN categories.