Premise of research. A two-phase fern spike occurred immediately after the Cretaceous-Paleogene (K/Pg) mass extinction event. Solely on the basis of palynological evidence, researchers have traditionally attributed the first phase of this spike to the proliferation of a single species of a Cyathea-like fern in the earliest Danian. This traditional perspective is challenged by recent investigations linking Anemia-like fern foliage with Cyathidites spores at K/Pg boundary localities in the Raton Basin, where the fern spore spike was first discovered by R. H. Tschudy. Although evidence emerging from neighboring basins appears to corroborate this new perspective, it remains to be seen whether this generalization applies to the northern Great Plains. Methodology. A comprehensive list of the most common fern megafossils collected from earliest Danian plant localities across western North America was compiled to determine the number and potential identity of Cyathidites-producing ferns. Pivotal results. Three K/Pg survivors commonly collected from basal Paleocene strata in western North America conceivably produced psilate, trilete (Cyathidites) fern spores essentially identical to those observed at the K/Pg boundary fern spore spike: Anemia elongata (Newberry) Knowlton, Dennastra sorimarginata McIver et Basinger, and the Coniopteris-like fern “Dennstaedtia” americana Knowlton. Conclusions. Arborescent ferns were not among the first plants in western North America to thrive in the immediate wake of ecological collapse at the K/Pg boundary. Basal polypod ferns can be linked to Cyathidites spores in the northern Great Plains, perhaps because of a latitudinal climatic gradient. These results could explain taxonomic inversion in the dual-phase fern spore spike between western North America and New Zealand.

中文翻译：

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白垩纪-古近纪大灭绝事件后第一批重新殖民北美西部的植物

研究的前提。白垩纪-古近纪 (K/Pg) 大灭绝事件后立即发生了两相蕨类植物尖峰。仅根据孢粉学证据，研究人员传统上将这一峰值的第一阶段归因于最早的大年时期一种类似 Cyathea 的蕨类植物的增殖。这种传统观点受到最近将贫血样蕨类植物叶子与拉顿盆地 K/Pg 边界位置的 Cyathidites 孢子联系起来的调查的挑战，其中蕨类孢子尖峰是由 RH Tschudy 首次发现的。尽管来自邻近盆地的证据似乎证实了这一新观点，但这种概括是否适用于大平原北部仍有待观察。方法。编制了从北美西部最早的大年植物产地收集的最常见蕨类植物巨型化石的综合清单，以确定产生 Cyathidites 的蕨类植物的数量和潜在身份。关键结果。通常从北美西部古新世地层收集的三个 K/Pg 幸存者可以想象产生的 psilate、trilete (Cyathidites) 蕨类孢子与在 K/Pg 边界蕨类孢子穗观察到的基本相同：Anemia elongata (Newberry) Knowlton, Dennastra sorimarginata McIver et Basinger 和 Coniopteris-like 蕨类植物“Dennstaedtia”美国诺尔顿。结论。在 K/Pg 边界的生态崩溃之后，树状蕨类植物并不是北美西部最早繁盛的植物之一。基底多足蕨可能与大平原北部的 Cyathidites 孢子有关，这可能是因为纬度气候梯度。这些结果可以解释北美西部和新西兰之间双相蕨类孢子穗的分类倒置。