The narrowly endemic endemic of Dagestan [6] ( Russia ), widespread in the Agul and Khiva regions [2] [7] . It grows in six natural areas, on wet shale rocks [2] .
Grassy [1] small fern with short rhizome. The length of the wai (leaves) is 6–12 cm. Spore-bearing in June – August [2] . Sporangia are located on the veins on the lower surface of the vaya [1] .
The Red Book of Russia
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Climate change in the areas where the species grows poses a threat to its existence. Kostenets of Dagestan is on the verge of extinction (“critically endangered”) according to the data of the International Union for Conservation of Nature . The area of growth sites is estimated at approximately 60 km²; the total number of copies is 1500–2500 (more than 250 copies in each subpopulation) [7] .
It is included in the Red Book of Russia [2] and the Republic of Dagestan (even earlier it was included in the Red Book of the RSFSR) [1] .
