Fertile Pinnae of Biscalitheca (Zygopteridales) from the Upper Pennsylvanian of the Appalachian Basin

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Abstract
Fertile ultimate pinnae of the zygopterid fern Biscalitheca Mamay are described from the Upper Pennsylvanian of Ohio. Ultimate pinnae measure 1.0-2.5 mm in diameter and produce pinnules, aphlebiae, and soral stalks as lateral structures. Vascularized aphlebiae are borne alternately along the adaxial pinna surface and are bifurcate apically. Pinnules are up to 3.0 mm long, have a deeply incised margin and are borne alternately along the pinna. A dense covering of scales clothes the adaxial pinna surface and aphlebiae bases. Pinnae have a rounded rectangular xylem strand with sunken adaxial protoxylem that branches laterally in an alternate fashion. Each lateral xylem trace branches to vascularize the 3 lateral appendages. Cylindrical soral stalks originate from the pinna, distal to the pinnule midvein. Distally, soral stalks become rectangular and branch to produce laterals that terminate in clusters of 7-60 sporangia each. Sporangia are musaform, 2.0-3.0 mm long, with 2 parallel lateral annuli extending from the base to near the tip. Dorsal sporangial walls have elongate branched patches of sclerenchyma. Dehiscence may occur through any non-annulus portion of the wall but usually occurs next to the annulus. Spores are spherical, trilete, 42-70 .mu.m in diameter, and have a verrucate ornamentation. Previously undescribed features of B. musata fertile pinnae are pinnules, adaxial aphlebiae and branching of the soral stalks. The specific diagnosis of B. musata is emended to incorporate these features. Affinities of the Ohio Biscalitheca are suggested to be with a zygopterid petiole (Etapteris) of a new type.