Taxonomical and palaeogeographic considerations on the seedfern genus Ptilozamites

A detailed study of the original (Nathorst and Antevs) material of the genus Ptilozamites was undertaken, both using macromorphology and epidermal anatomy. The 9 species present in the original collection (Ptilozamites blasii (Brauns) Nathorst, P. carlsonii Nathorst, P. heeri Nathorst, P. falcatus Nathorst, P. fallax Nathorst, P. linearis Nathorst, P. nilssonii Nathorst, P. oldhamii Nathorst, P. triangularis Nathorst) have been reduced to three species (P. blasii (Brauns) Nathorst, P. heeri Nathorst, P. nilssonii Nathorst). Moreover, the new combination Ptilozamites sandbergeri (Schenk) nov. comb. was made together with an emended diagnosis. Various other species are now omitted from the genus Ptilozamites; P. acuminatus Nathorst and P. acutangulatus Nathorst are conspecific and belong unequivocally, due to the cuticular pattern, to the genus Anomozamites. Ptilozamites chinensis Hsu has been transferred to Pseudoctenis chinensis (HSU) n. comb. Also some other species, sometimes attributed to Ptilozamites, are discussed and their attributions to other genera such as Dicroidium and Ctenozamites. The genus Ptilozamites, once considered restricted to the Rhaeto-Liassic is now reported also from the Middle Triassic, but the largest distribution of the genus remains in the Rhaeto-Liassic and is restricted to the Northern Hemisphere. Finally, the relationships with the macromorphologically related genera Anomozamites, Dicroidium, Pseudoctenis and Ctenozamites are discussed.