Two new species of Scolecopteris (Marattiales), sources of Torispora securis Balme and Thymospora thiessenii (Kosanke) Wilson et Venkatachala

Abstract

Two biostratigraphically significant miospore species, Thymospora thiessenii and Torispora securis , were isolated from marattialean synangia preserved in coal-ball permineralizations from Pennsylvanian strata of the Illinois Basin and Western Interior coal region. Synangia containing Thymospora thiessenii were recovered from the Missourian Parker Coal Member (Patoka Formation) of Indiana and are described here as Scolecopteris parkerensis Lesnikowska et Willard, sp. nov. The uniformly thin outer sporangial walls and broadly enclosing, hirsute pinnule margins place the species in the Latifolia group sensu Millay (1979). It is distinguished from the other species of the group by the size of the synangia, by the size and shape of the pinnules, by features of the pedicel and by the spores. Coal balls from the Desmoinesian Cliffland Coal Member (Kalo Formation) of Iowa yielded synangia producing two different spore types: a peripheral layer of spores with a distinct apical crassitude ( Torispora securis ) and interior spores assignable to Laevigatosporites globosus . The crassitude of Torispora is shown to be a structure distinct from the main spore body but is enclosed with it by the exine. The fructifications are described as Scolecopteris dispora Lesnikowska et Willard, sp. nov. , which belongs to the Oliveri group sensu Millay (1979) on the basis of the uniformly thick outer sporangial wall and downturned, hairless pinnule margins. It is distinguished from the other members of the group by the large size of the synangia, the uniform histology of the outer sporangial walls, features of the pedicel, and by the spores. This is the first reported association of either of these spores with permineralized fructifications from coal.