Leary R L
Science. 1990 Sep 7;249(4973):1152-4. doi: 10.1126/science.249.4973.1152.
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.
莱斯利蕨属（Lesleya）的一个标本，此前仅作为孤立的不育叶被知晓，现已发现其在叶柄相对两侧有两排着生胚珠的花托。该标本来自伊利诺伊州西部的宾夕法尼亚纪下部（纳缪尔阶B或C）。这个标本的可育部分类似于来自堪萨斯州和得克萨斯州二叠纪下部的堪萨斯拟苏铁（Phasmatocycas kansana Mamay），马迈将其解释为苏铁类的祖先形态。吉莱斯皮和费弗科恩发现拟苏铁附着在带羊齿（Taeniopteris）的基部。叶部，即莱斯利蕨属和带羊齿，有许多共同特征；主要形态差异在于叶脉的弯曲度。莱斯利蕨属及其附着的可育叶柄被认为是带羊齿和拟苏铁的祖先，最终也是现代苏铁的祖先。这将已知苏铁类前身的年代从二叠纪早期追溯到宾夕法尼亚纪早期（约3.2亿年前），大约早了3500万年。
