The term "Sarmatians" is believed to refer to various horse-riding peoples from the territory of present-day Iran. From the 3rd century BC, they settled in present-day southern Russia and Ukraine, where they displaced the Scythians. From the 3rd century onward, Sarmatian tribes also settled in the Roman Empire, often adopted Roman citizenship and served in Roman legions, having been hired as auxiliary troops. In Britain, for example, the Sarmatians defended Hadrian's Wall against the attacks of the Scottish Picts. The photograph shows the gravestone of a Sarmatian horseman from the Roman settlement of Deva Victrix (in present-day Chester in northern England).
Gravestone of a Sarmatian horseman who fought for the Romans in Britain, Grosvenor Museum, Chester, England, colour photograph, 2011, photographer: Wolfgang Sauber; image source: Wikimedia Commons, Creative Commons Attribution-Share Alike 3.0 Unported.