Bipinnate Ptilozamites nilssonii from Jameson Land and new considerations on the genera Ptilozamites Nathorst 1878 and Ctenozamites Nathorst 1886

Newly collected Rhaetian plant compressions of the seed fern Ptilozamites nilssonii Nathorst 1878 from Jameson Land, Eastern Greenland, revealed both simple and forked, unipinnate and bipinnate morphologies, indicating a closer relationship between the genera Ptilozamites Nathorst 1878 and Ctenozamites Nathorst 1886 than previously documented. Cuticle analysis revealed micromorphological traits typical of simply pinnate P. nilssonii on bipinnate leaf forms, yet up until the discovery of this material Ptilozamites has never been considered bipinnate. In 1886, the genus Ctenozamites was erected for species similar in epidermal characters to Ptilozamites, but presenting a typical bipinnate character, rarely or never unipinnate. As the new Greenland material collected from South Tancrediakløft and Astartekløft have shown, both genera are now very strongly related anatomically, and therefore identical from a systematic point of view. We therefore propose the use of the genus Ptilozamites as Ctenozamites Nathorst 1886 is a synonym of Ptilozamites Nathorst 1878.