厚脉栉羊齿(Pecopteris lativenosa Halle emend. Li et al.)自1927年建立以来, 在华北晚古生代陆相地层中多有报道, 但皆为不完整的营养羽片, 且形态差异较大, 导致其鉴定较为混乱。本文依据内蒙古乌达煤田太原组火山凝灰岩植物群(即二叠纪“植物庞贝”)中大量较为完整的厚脉栉羊齿标本, 探讨其羽状复叶的完整形态; 在前人研究的基础上将该种末次羽片形态分为UP₃、UP₇、UP₂和UP₁共4种类型, 末二次羽片分为PP₁、PP₂、PP₃、PP₄、PP₅和PP₆共6种类型。对厚脉栉羊齿的三次羽状复叶进行了复原, 修订了各级羽片的鉴定依据, 并补充了变态叶和茎干等相关信息。与该种的模式标本进行对比, 推测模式标本中各羽片类型可能代表了复叶末三级轴顶部的PP₂型和PP₃型末二次羽片, 为厚脉栉羊齿的鉴定提供了依据。

Pecopteris lativenosa Halle emend. Li et al. has been widely reported from the upper Paleozoic of North China. However, all previously reported specimens are incomplete with great morphological variation, leading to frustration in their identifications. In recent years, an autochthonous early Permian swamp forest, the Wuda Tuff flora, has been discovered from the volcanic tuff layer between coal No. 6 and coal No. 7 in Wuda Coalfield, Inner Mongolia. This flora has yielded large, relatively complete specimens with fine anatomical details, enabling an in-depth evaluation of intraspecific morphological variation of Pecopteris lativenosa. In this report, the ultimate pinnae of Pecopteris lativenosa are divided into four types: UP₃, UP₇, UP₂, and UP₁; penultimate pinnae are divided into six types: PP₁, PP₂, PP₃, PP₄, PP₅, and PP₆. On a penultimate rachis, ultimate pinnae vary from apex to base in a sequence of undivided, pinnatifid, pinnatipartite and pinnatisect types, with UP₃, UP₇, and UP₂ all located on the apical part of the penultimate pinna. Penultimate pinnae on an antepenultimate rachis also vary from apex to base in a sequence of undivided, pinnatifid, pinnatipartite and pinnatisect types, with PP₆, PP₅, PP₄, PP₃, and PP₂ all located on the apical part of the antepenultimate pinna. On an antepenultimate pinna, the basal penultimate pinnae are about 20 cm long, shorter than those penultimate pinnae in the middle, which are about 47 cm long. A pair of aphlebiae are attached at the base of the antepenultimate rachis. Based upon these observations, an entire tripinnate frond of Pecopteris lativenosa is reconstructed. In addition, the leaf scars are arranged in two longitudinal rows, showing the Caulopteris obovatus type. The type specimens described by Halle in 1927 likely represent penultimate pinna types PP₂ and PP₃ from the distal parts of antepenultimate pinnae.

国家自然科学基金委重点项目(42230210)和中国科学院南京地质古生物研究所古生物学与油气地层应用重点实验室开放基金 (213127)联合资助