Abstract The former family Taxodiaceae is currently treated as nine genera in five subfamilies of the family Cupressaceae. Pollen of the ‘taxodiaceous’ Cupressaceae typically has a papilla in the leptoma area and is common in Cenozoic strata because some of its genera were key elements in lignite forming swamp forests. Dispersed fossil pollen of this group are often assigned to particular genera and, based on the modern ecologies of these taxa, to particular palaeoenvironments. In this study, we investigated pollen of all nine genera of the former Taxodiaceae using light and scanning electron microscopy to evaluate whether pollen morphology can be used to discriminate modern genera of this paraphyletic group. We found few genus- or subfamily-diagnostic characters among members of taxodiaceous Cupressaceae. Features such as orbiculae and pollen and leptoma size cannot be used to discriminate subfamilies. However, three basal subfamilies share short papillae, whereas in two more derived clades (Sequoioideae and Taxodioideae) papillae are markedly longer. In the generally non-papillate core Cupressaceae, the leptoma (aperture) area may or may not possess a distinct circular thinning as also found in the basal grade of taxodiaceous Cupressaceae. Our results show that it is difficult if not impossible to distinguish genera of the ecologically distinct Taxodioideae and Sequoioideae based on pollen morphology. In view of a much wider ecological amplitude of many taxodiaceous Cupressaceae during large parts of the Cenozoic, we conclude that it is not recommendable to infer particular palaeoenvironments on the basis of dispersed taxodiaceous pollen grains alone.

中文翻译：

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乳头状柏科花粉（原紫杉科）的低分类分辨率损害了它们在古生境重建中的适用性

摘要 原紫杉科目前被归为柏科5个亚科的9个属。“紫杉科”柏科的花粉通常在 Leptoma 区域有一个乳头，在新生代地层中很常见，因为它的一些属是形成沼泽森林的褐煤的关键元素。该组散布的花粉化石通常属于特定属，并且根据这些分类群的现代生态，属于特定的古环境。在这项研究中，我们使用光学和扫描电子显微镜研究了前杉科所有九个属的花粉，以评估花粉形态是否可用于区分该并系群的现代属。我们在分类柏科的成员中发现了很少的属或亚科诊断特征。不能使用轮状花粉和花粉以及瘦肉瘤大小等特征来区分亚科。然而，三个基部亚科共享短乳头，而在两个更衍生的进化枝（红杉亚科和杉木亚科）中，乳头明显更长。在通常无乳头状的核心柏科中，如在紫杉科的基部级中也发现的那样，细瘤（孔）区域可能具有也可能不具有明显的圆形变薄。我们的结果表明，根据花粉形态区分生态上不同的杉科和红杉科的属是很困难的。鉴于在新生代的大部分地区，许多分类科柏科的生态范围要广得多，