When validated in 1968, the fossil-species included several formerly validly published species in synonymy (and therefore nomenclaturally illegitimate and superfluous), viz. Populus latior A. Braun (in Neues Jahrb. Mineral. Geognosie 1845(2): 169. 1845), Populus transversa A. Braun in Stizenb. Uebers. Verstein. Baden: 80. 7-10 May 1851, Populus aeoli Unger, Gen. Sp. Pl. Foss. 416. 18 Apr 1850, Populus heliadum Unger, Gen. Sp. Pl. Foss. 416. 18 Apr 1850, Populus attenuata A. Braun in Unger, Gen. Sp. Pl. Foss. 417. 18 Apr 1850.