Possible Early Pennsylvanian Ancestor of the Cycadales

Abstract

A specimen of Lesleya, previously known only as isolated sterile foliage, has been found with two rows of ovule-bearing receptacles on opposite sides of the petiole. This specimen is from the Lower Pennsylvanian (Namurian B or C) of western Illinois. The fertile portion of this specimen is similar to Phasmatocycas kansana Mamay from the Lower Permian or Kansas and Texas, which Mamay interpreted as an ancestral form to cycads. Phasmatocycas was found attached to the base of Taeniopteris by Gillespie and Pfefferkorn. The foliar portions, Lesleya and Taeniopteris have many features in common; the major morphologic difference is curvature of the veins. Lesleya and its attached fertile petiole are proposed as ancestors of Taeniopteris and Phasmatocycas, and ultimately, the ancestors of modern cycads. This extends the age of known precursors of cycads back from the Early Permian to early Pennsylvanian (about 320 million years ago), approximately 35 million years earlier.