Alxa League
In 1966 Rozhdestvensky also named a second species, "Probactrosaurus alashanicus", based on fragmentary material. Its specific name refers to the Alxa League. In 2002 David B. Norman published a revision of the genus, in which he reported the holotype specimen of "P. alshanicus", the back of a skull, had been lost after being dispatched from Moscow to Beijing. He concluded that the species was a synonym of "P. gobiensis".