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 of 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.

LesleyaLesquereux from the Pennsylvanian of the Iberian Massif: part of a dryland megaflora from the Variscan orogen, northwestern Portugal

“…Its familial and ordinal affinities are unknown (e.g., Taylor et al 2009), whereas at the class level Lesleya variously has been assigned to, or allied with, both the Cycadopsida and Pteridospermopsida Remy 1977, 1978;Leary 1990). A relationship between Lesleya and Permian-Mesozoic cycads has been suggested on the basis of their similar foliage (e.g., Florin 1933; Remy and Remy 1978;Leary 1990Leary , 1993Leary , 1998Wagner 2004;Taylor et al 2009). Lesleya also has been suggested as a probable ancestor to cycads (Remy and Remy 1978;Leary 1990;Taylor et al 2009).…”

“…A relationship between Lesleya and Permian-Mesozoic cycads has been suggested on the basis of their similar foliage (e.g., Florin 1933; Remy and Remy 1978;Leary 1990Leary , 1993Leary , 1998Wagner 2004;Taylor et al 2009). Lesleya also has been suggested as a probable ancestor to cycads (Remy and Remy 1978;Leary 1990;Taylor et al 2009). Florin (1933) regarded Lesleya as a primitive gymnosperm, however, it is not closely related to Permian seed ferns or Mesozoic gymnosperms based on morphological and epidermal features.…”

“…Florin (1933) regarded Lesleya as a primitive gymnosperm, however, it is not closely related to Permian seed ferns or Mesozoic gymnosperms based on morphological and epidermal features. In addition, D r a f t differences between the two groups in their venation patterns (anastomosed/reticulated venation in Glossopteris versus pinnatifid/pinnate venation in Lesleya) and reproductive organs (e.g., Leary 1990Leary , 1993Leary , 1998. margins strongly arched towards the leaf base; base long and narrow (cuneate); margin entire; midvein broad, 1.0 to 3.0 mm wide; lateral veins fork once or twice; lateral veins oblique, slightly curved (arched) with a 7° to 15° angle at the midvein and 5º to 35º angle on margin; 10-13 veins per cm on margin.…”

Cyclic changes in Pennsylvanian paleoclimate and effects on floristic dynamics in tropical Pangaea

“…Compositionally the diagnostic elements of these floras are the foliage types Megalopteris and Lesleya, thought to be seed plants (Leary and Pfefferkorn, 1977;Leary, 1990). From published illustrations, some of the plants initially identified as Megalopteris appear, in fact, to be Lesleya, based on leaf-venation patterns.…”

The Enigmatic Paleozoic plants Spermopteris and Phasmatocycas reconsidered

“…However, S. jonkeri is known only from one poorly preserved specimen, and the interpretations of this fossil are therefore tentative. Leary (1990) described what he interpreted as fertile specimens of Lesleya from the Lower Pennsylvanian (Namurian B or C) of Illinois. Structures termed ovulate receptacles occur laterally along the petiole.…”