The taxonomy, micromorphology, kaiyology and evolutionary relationships of Taraxacum bithynicuni were studied using the original material and new samples from the summit area of Mt. Uludag, Bursa Province, Turkey. It is sexual with 2n=16, considerably isolated in outer phyllary and achenc characters. The nrDNA ITS Neighbor Net analysis shows relationships of T. bithynicum with members of T. sect. Scariosa. Taraxacum bithynicum is considered as a taxon endemic to the summit area of Uludag. The exploration of the latter area also revealed another, probably related but agamospennous and triploid (2n=24) species that is decribed here as T pseudobithynicum, also confined to Uludag. The endemism in the Mt. Uludag flora is briefly characterized, and the two species studied are expected to be related to other similar plants restricted to mountain areas of SW and S Anatolia. The history of the original gathering of T bithynicum (Aucher-Eloy, no. 3540) and various concepts of this name in the literature are briefly discussed.