Eostrix tsaganica was named by Kurochkin and Dyke (2011). Its type specimen is PIN 3104/129, a limb element (distal end of a left tarsometatarsus with portion of shaft), and it is a 3D body fossil. Its type locality is Tsagaan Khushuu (PIN collection 3104), which is in an Eocene terrestrial horizon in the Naran Bulak Formation of Mongolia.