Here we describe mandibular, dental, and postcranial remains referable to Rhinocerotidae and Chalicotheriidae (Perissodactyla) originating from the vertebrate localities of Küçükçekmece East and Küçükçekmece West, in Thrace (European Turkey). The four rhinocerotids recognized comprise the early diverging Ronzotherium sp. (one lower molar, reworked from Oligocene deposits; Küçükçekmece West), the two-horned rhinocerotine Ceratotherium neumayri (Osborn, 1900), and two small chilothere aceratheriines: Chilotherium schlosseri (Weber, 1905) and Persiatherium sp. A chalicotheriine chalicotheriid, Kalimantsia sp., is documented by two tooth fragments and an unfused second phalanx of undoubtful affinities in Küçükçekmece West. This occurrence substantiates the record of Kalimantsia, previously restricted to the type locality Kalimantsi-Pehsata, in SW Bulgaria, and allows notably for the first recognition of postcranial remains for this taxon. Although distinct in terms of taxonomic composition and relative abundance, the rhinocerotid assemblages of Küçükçekmece East and Küçükçekmece West are in total agreement with a single biostratigraphical age, estimated to be correlated with the late Vallesian MN10 zone.
Rhinocerotidae, Chalicotheriidae, reworked Ronzotherium, late Vallesian, Istanbul region, paleobiogeography.