A new marattialean fern Diplazites campbellii sp. nov. and its in situ spores from the Pennsylvanian of the Sydney Coalfield, Nova Scotia, Canada

The eusporangiate fern order Marattiales are represented in the living flora by the family Marattiaceae but have an extensive fossil record stretching back to the Carboniferous. The family Psaroniaceae included important wetland plants in the Carboniferous and Permian. In this work we present a new member of the Psaroniaceae from the Lloyd Cove Seam of the Brogan's Mine, Sydney Coalfield, Nova Scotia, Canada dated to the Kasimovian Stage (lower Stephanian, Pennsylvanian) of the Carboniferous. The new fern is represented by a small specimen with distinctive fertile pinnules and reproductive organs including large synangia that possess a well-developed synangial sheath with a central parenchymatous filling. Small monolete in situ spores are compared to the dispersed miospore species Punctatosporites pygmaeus. Based on well preserved reproductive organs, we are proposing a new species Diplazites campbellii sp. nov. A new evolutionary model combining species that produced the smallest monolete spores and significant characters of their reproductive organs is suggested. Four following subgroups are suggested: the Unita, Hemitelioides, Multisporangiate and Crenulopteris.