Abstract Microcoprolites of Palaxius salataensis are non-skeletal carbonate grains produced by callianassid shrimps. This ichnospecies is recognized by four longitudinal canals arranged around a bilateral plane of symmetry, with crescent outline in cross-section. Palaxius salataensis has been previously reported from other countries and in strata from the late Paleozoic to the Mesozoic. In this study, we describe the first Aptian record of the ichnospecies, the first Cretaceous occurrence in North America, and the fifth occurrence worldwide. Palaxius salataensis was found in a packstone-grainstone with abundant pellets and common gastropod shell fragments and subangular, poorly sorted intraclasts. The paleoenvironment was characterized by shallow-waters with high energy conditions, occurring between fair-weather wave base and storm wave base, close to the platform margin, where well-oxygenated and nutrient-rich conditions predominated. The microcoprolite-rich bed of the La Huasteca Canyon occurs on top of an oolitic grainstone interval in the upper levels of the Cupido Formation, interpreted as the termination of the early Aptian Oceanic Anoxic Event 1a (OAE 1a). The presence of P. salataensis in the upper levels of the Cupido Formation is directly related to the availability of organic matter rather than to oxygen recovery.

中文翻译：

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墨西哥东北部阿普蒂安（下白垩纪）微粪化石 Palaxius salataensis 的首次出现及其古生态意义

摘要 Palaxius salataensis 的微粪粒是由对虾产生的非骨骼碳酸盐颗粒。这种鱼种的特征是四个纵向运河围绕一个双边对称平面排列，横截面呈新月形轮廓。Palaxius salataensis 以前在其他国家和晚古生代到中生代的地层中都有报道。在这项研究中，我们描述了鱼类物种的第一个 Aptian 记录、北美的第一个白垩纪事件和世界范围内的第五个事件。Palaxius salataensis 被发现在具有丰富颗粒和常见腹足动物壳碎片和亚角、分类不良的碎屑的灰岩-粒岩中。古环境以浅水、高能条件为特征，发生在晴天波基和风暴波基之间，靠近平台边缘，那里充氧良好和营养丰富的条件占主导地位。La Huasteca 峡谷富含微粪化石的床位在 Cupido 组上层的鲕粒岩层之上，被解释为早期 Aptian 海洋缺氧事件 1a (OAE 1a) 的结束。在 Cupido 组上层的 P. salataensis 的存在与有机物质的可用性直接相关，而不是与氧气回收率相关。