Abstract Echitriporites trianguliformis and E. suescae comb. nov. are two species of proteaceous-like triaperturate pollen that have been widely reported in several sedimentary sequences from northern South America, especially in Colombia and Venezuela. Despite their biostratigraphic significance and because of their morphological similarity, distinction between the two species has been difficult, leading to a biased understanding of their chronostratigraphic ranges. In this study, we compare 75 pollen grains spanning the Maastrichtian–Danian time interval through traditional and geometric morphometrics, and a newly proposed Procrustes-based method (index of pollen curvature). Traditional assessments show subtle variation between specimens; however, geometric morphometrics and the curvature index allow quantifying morphological differences in the degree of concavity-convexity through time. Therefore, geometric morphometrics and curvature index results enable us to constrain the stratigraphic ranges of both taxa. We suggest a coetaneous range for E. trianguliformis and E. suescae comb. nov. during the Late Cretaceous, but the presence of only E. trianguliformis after the Cretaceous–Paleogene boundary event. In addition, we propose a threshold value of 1.5 µm for the curvature index as a tool for distinguishing between these two taxa. We conclude that the combination of geometric morphometrics and the curvature index provides a powerful tool to distinguish between morphological closely-related pollen taxa that are difficult to distinguish through both light microscope visual comparisons and statistical analysis of morphometric measurements.

中文翻译：

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南美洲北部白垩纪-古近纪边界的两个关键生物地层类蛋白质类花粉类群的形态变异

摘要 Echitriporites trianguliformis 和 E. suescae 梳。十一月 是两种类似蛋白质的三孔花粉，已在南美洲北部的几个沉积序列中得到广泛报道，特别是在哥伦比亚和委内瑞拉。尽管它们具有生物地层学意义并且由于它们的形态相似性，但很难区分这两个物种，导致对其年代地层范围的理解有偏见。在这项研究中，我们通过传统和几何形态测量学以及新提出的基于 Procrustes 的方法（花粉曲率指数）比较了跨越马斯特里赫特-大年时期的 75 粒花粉粒。传统评估显示样本之间存在细微差异；然而，几何形态计量学和曲率指数允许量化凹凸程度随时间的形态差异。因此，几何形态测量学和曲率指数结果使我们能够限制两个类群的地层范围。我们建议 E. trianguliformis 和 E. suescae 梳的同生范围。十一月 在晚白垩世期间，但在白垩纪-古近纪边界事件之后仅存在 E. trianguliformis。此外，我们建议曲率指数的阈值为 1.5 µm，作为区分这两种分类群的工具。