Department of Geology and Geophysics, Yale University, New Haven, CT, USA.
Department of Geology, Colorado College, Colorado Springs, CO, USA.
Geobiology. 2020 Jul;18(4):486-496. doi: 10.1111/gbi.12387. Epub 2020 Apr 3.
Morphologically complex trace fossils, recording the infaunal activities of bilaterian animals, are common in Phanerozoic successions but rare in the Ediacaran fossil record. Here, we describe a trace fossil assemblage from the lower Dunfee Member of the Deep Spring Formation at Mount Dunfee (Nevada, USA), over 500 m below the Ediacaran-Cambrian boundary. Although millimetric in scale and largely not fabric-disruptive, the Dunfee assemblage includes complex and sediment-penetrative trace fossil morphologies that are characteristic of Cambrian deposits. The Dunfee assemblage records one of the oldest documented instances of sediment-penetrative infaunalization, corroborating previous molecular, ichnologic, and paleoecological data suggesting that crown-group bilaterians and bilaterian-style ecologies were present in late Ediacaran shallow marine ecosystems. Moreover, Dunfee trace fossils co-occur with classic upper Ediacaran tubular body fossils in multiple horizons, indicating that Ediacaran infauna and epifauna coexisted and likely formed stable ecosystems.
形态复杂的痕迹化石记录了两侧对称动物的底栖活动，在显生宙的地层中很常见，但在埃迪卡拉纪的化石记录中却很少见。在这里，我们描述了位于美国内华达州登菲山（Mount Dunfee）下深泉组下部登菲段（Dunfee Member）的一个遗迹化石组合，其位于埃迪卡拉纪-寒武纪界线以下 500 多米处。尽管规模在毫米级，且在很大程度上不破坏结构，但登菲组合包括复杂的、穿透沉积物的痕迹化石形态，这些形态是寒武纪沉积物的特征。登菲组合记录了有记载的最早的穿透沉积物的底栖动物化石实例之一，这与之前的分子、遗迹学和古生态学数据一致，表明冠群两侧对称动物和两侧对称动物样的生态系统存在于晚埃迪卡拉纪浅海生态系统中。此外，登菲遗迹化石与经典的上埃迪卡拉纪管状身体化石在多个层位中共同出现，表明埃迪卡拉纪的底栖动物和浮游动物共存，并可能形成了稳定的生态系统。
