Abstract The Barremian–Aptian Paja Formation, as exposed in Villa de Leyva and nearby areas (Boyaca, Colombia), is one of the most fossiliferous Cretaceous units in northern South America, yet no fossil crabs had ever been recorded from this formation in the region. Here we report the first occurrence of crabs from the upper Aptian “Arcillolitas con nodulos huecos” Member of the Paja Formation in Boyaca, belonging to two species of orithopsid crabs: Bellcarcinus aptiensis Luque, 2014 and Planocarcinus olssoni ( Rathbun, 1937 ). The newly collected material — represented by dozens of samples in small nodules — includes individuals preserving key rostral, orbital and pereonal traits previously unknown from the type material. Furthermore, a few specimens of B. aptiensis have swellings in their branchial regions, consistent with the deformation produced by parasitic isopods infesting the crab's gill chambers. To our knowledge, this is the first record of parasitic isopod traces in the family Orithopsidae, and the oldest evidence of isopod parasitism in raninoidan crabs. The new material here reported increases the number or marine arthropods known from the fossiliferous Paja Formation in Boyaca and provides valuable information for further palaeoecological reconstructions of these shallow-marine settings in northern South America during the Early Cretaceous.

中文翻译：

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来自博亚卡（哥伦比亚）下​​白垩统 Paja 组的 Orithopsid 螃蟹，以及 Raninida 中最早的寄生等足类动物痕迹记录

摘要 Barremian-Aptian Paja 地层出露在 Villa de Leyva 和附近地区（哥伦比亚博亚卡），是南美洲北部白垩纪化石含量最高的单元之一，但该地区从未记录到此地层中的螃蟹化石. 在这里，我们报告了博亚卡 Paja 组上部 Aptian“Arcillolitas con nodulos huecos”成员的首次出现，属于两种原石蟹：Bellcarcinus aptiensis Luque, 2014 和 Planocarcinus olssoni (Rathbun, 1937)。新收集的材料 - 由数十个小结节样本代表 - 包括保留以前从类型材料中未知的关键喙、眼眶和腓骨特征的个体。此外，一些 B. aptiensis 的标本在鳃区有肿胀，与寄生等足类动物侵扰螃蟹鳃室所产生的变形一致。据我们所知，这是 Orithopsidae 科中寄生等足类动物踪迹的第一个记录，也是雷尼伊丹蟹中等足类动物寄生的最古老证据。此处报道的新材料增加了从博亚卡的含化石 Paja 组中已知的海洋节肢动物的数量，并为早白垩世期间南美洲北部这些浅海环境的进一步古生态重建提供了有价值的信息。