A new diatom (Bacillariophyta) species-<i>Fallacia cinariana</i><i> sp.</i><i> nov.</i>-from Kaklık Cave in the Western Anatolian Karst Region, Republic of Türkiye

A new Fallacia cinariana sp. nov. is described from a unique extreme microenvironment in the highly calcareous Kaklik Cave, Pamukkale Travertines in the Western Anatolian Karst Region, Turkiye with calcareous (pH 8.2) rich waters. Valves of F. cinariana are small (<15 um), linear to linear-elliptic with rounded ends. As with the type species for the genus (F. pygmaea (Kutzing) Stickle & D.G.Mann), the axial area is composed of a narrow raphe sternum and valve face slits/ occlusions on either side, 500-900 nm length. The striae are biseriate and form around a small round to elliptic central area. Falacia subhamulata Lange-Bertalot from Europe is considered the closest morphologically aligned species being larger, wider, broader central area, elliptic to round valve face slits/opening, and fewer biseriate striae. Other comparable taxa include Fallacia subhamulata (Grunow) D.G.Mann, F. angarae, Metzeltin, Kulikovskiy & Lange-Bertalot, F. helenensis (Schulz) D.G.Mann, F. lange-bertalotii Reichardt, F. lenzii Lange-Bertalot and F. pseudohelensis Kulikovskiy, Metzeltin & Lange-Bertalot. Among them, Fallacia lange-bertalotii (originally described from the Europe) co-occurs in Kaklik Cave and is similar, but F. cinariana has different morphological characters and distinct valve face slits/occlusions.