New fossil woods from the Keuper of Poland and France are assigned to Agathoxylon keuperianum (Unger) nov. comb. A complete nomenclatural treatment of this taxon is given, with up-dated nomenclatural synonymy and some taxonomical notes. It is shown that Zimmermann's choice of a lectotype (1953) for this species is superseded by material in the Unger collection at the Paris Muséum National d'Histoire Naturelle (France). Taxomical reappraisal of Unger collection also evidenced that Simplioxylon hungaricum Andreanzsky correct name is Simplicioxylon wurtembergicum (Unger) nov. comb. and that Peuce brauneana Unger can be excluded from Agathoxylon keuperianum synonymy. Literature data for Agathoxylon keuperianum are reviewed and some are invalidated. Our new data are the first safe reports for this species outside from Germany. The systematic position of Agathoxylon keuperianum is discussed, as well as its stratigraphical and geographical range. In the present state of knowledge it seems to be restricted to the area where German Keuper is deposited. Anatomical features suggest that Agathoxylon keuperianum thrived under warm and wet conditions, whereas German Keuper sediments globally suggest hot and dry climate.