Data from: Linguliform brachiopods across a Cambrian–Ordovician (Furongian–Early Ordovician) biomere boundary: the Sunwaptan/Skullrockian North American stage boundary in the Wilberns and Tanyard Formations of central Texas

The Cambrian-Ordovician Diversity Plateau, between the Cambrian Explosion and the Ordovician Radiation, is punctuated by a series of well-documented Laurentian trilobite extinction events. These events define the bounding surfaces of trilobite “biomeres” that correspond to North American stages, including those of the Sunwaptan and Skullrockian. Trilobites show a consistent pattern of recovery across these boundaries, and commonly each extinction and replacement of taxa is interpreted as a single event as changing environmental conditions spurred shoreward migration of shelf or oceanic faunas that displaced established cratonic faunas. Linguliform brachiopods are also abundant in strata of this interval, and we investigate their stratigraphic distribution across the Sunwaptan–Skullrockian Stage boundary in Texas through high-resolution stratigraphic sampling of subtidal sediments. We document complete genus- and species-level turnover of the linguliform brachiopod fauna coincident with trilobite extinction events, suggesting that these brachiopods were affected by the same factors that affected trilobites. The Skullrockian replacement fauna was cosmopolitan, with ties to Gondwana and Kazakhstan and to the Laurentian shelf environment. The timing of appearances of taxa suggests that the faunal migration onto the Laurentian shelf came from elsewhere during a transgression. The disappearance of the Sunwaptan fauna and the arrival of the Skullrockian fauna are distinct events. We suggest that “biomere” events may be complex, and the cause of the extinction is not necessarily the same event that facilitates the appearance of a replacement fauna. We describe one new species, Schizambon langei.

寒武-奥陶纪生物多样性停滞期（Cambrian-Ordovician Diversity Plateau）处于寒武纪大爆发与奥陶纪生物大辐射之间，被一系列有充分实证记录的劳伦大陆（Laurentian）三叶虫灭绝事件所间断。这些事件界定了对应北美地层阶（包括桑瓦普坦阶（Sunwaptan）与斯卡尔罗基安阶（Skullrockian））的三叶虫“生物域（biomeres）”的边界。三叶虫在这些界线处展现出一致的复苏模式，学界通常将分类群的每次灭绝与更替视作单一事件：环境变化推动陆棚或海洋群落向岸迁移，取代了原有的克拉通群落（cratonic faunas）。舌形贝型腕足动物（Linguliform brachiopods）在该时段地层中同样富集，本研究通过对德克萨斯州潮下沉积物的高分辨率地层采样，探究了其在桑瓦普坦阶-斯卡尔罗基安阶界线处的地层分布特征，记录到与三叶虫灭绝事件同步的腕足动物群完整属种级更替现象，暗示这类腕足动物受到了与三叶虫相同的环境因素影响。斯卡尔罗基安阶的更替动物群具有广布性，与冈瓦纳大陆（Gondwana）、哈萨克斯坦及劳伦大陆陆棚环境存在演化关联；类群出现时序表明，海侵期间这批动物群从其他区域迁入劳伦大陆陆棚。桑瓦普坦动物群的消失与斯卡尔罗基安动物群的出现是两个独立的地质事件。本研究提出，“生物域（biomeres）”事件可能具有复杂性，灭绝事件的成因未必与促进更替类群出现的过程为同一事件。本文还记述了一个新种：朗氏裂瓣贝（Schizambon langei）。