Article: A new permineralized marattialean fern from the Pennsylvanian of Illinois
Ironstone nodules from a Middle Pennsylvanian locality near Carterville (Illinois) have yielded both fertile and sterile foliage of a new species of Scolecopteris. Permineralized specimens were studied utilizing polished surfaces and a modified liquid peel technique. Scolecopteris macrospora sp. nov. has ovate-elongate pinnules measuring 2-9 mm long and 2-5 mm wide, with a strong midvein that produces seldom-branched laterals that meet the margin at a 60° angle. Synangia are borne abaxially in a single row on each side of the midrib on pinnules with dissected margins. Synangia are composed of four to five radially arranged, closely appressed sporangia with acute apices. The outer-facing sporangial walls are one to two cells in thickness basally and become progressively thicker distally, spores range from 42 to 66 p.m in diameter and possess a prominent trilete suture and papillate sculpturing. The new species appears similar to S. elegans and S. minor, but differs in the greater amount of sterile tissue present centrally in the synangium, in foliage type, and in spore morphology.