Morphometric analysis of Skiagia-plexus acritarchs from the early Cambrian of North Greenland

The Cambrian evolutionary radiations are marked by spectacular biotic turnovers and the establishment of increasingly tiered food chains. At their base are primary producers, which in the Cambrian fossil record are chiefly represented among organic-walled microfossils. The majority of these microfossil remains have traditionally been attributed to an informal category of incertae sedis called “acritarchs”, based entirely on form taxonomy. Acritarch form-taxa have been intensely used for biostratigraphy, and in large-scale studies of phytoplankton diversity. However, both prospects have been challenged by cases of taxonomic inconsistencies and over-splitting arising from the large phenotypic plasticity seen among these microfossils. The acritarch form-genus Skiagia stands as an ideal case-study to explore these taxonomic challenges, since it encompasses a number of form-species widely used in lower Cambrian biostratigraphy. Moreover, subtle morphological differences among Skiagia species...

寒武纪演化辐射事件以显著的生物更替及层级愈发复杂的食物链构建为核心特征。该事件的基底为初级生产者，在寒武纪化石记录中，这类生产者主要以有机壁微化石的形式得以保存。长期以来，这类微化石残骸的绝大多数被归入非正式的分类未定（incertae sedis）类群——疑源类（acritarchs），其分类完全基于形态分类学方法。疑源类的形态分类单元长期被广泛应用于生物地层学（biostratigraphy）研究以及浮游植物多样性的大规模宏观分析中。然而，由于这类微化石存在显著的表型可塑性（phenotypic plasticity），由此引发的分类不一致与过度划分现象，对上述两类应用场景均提出了挑战。疑源类形态属（form-genus）Skiagia是探究此类分类学难题的理想案例研究对象，该属包含多种广泛应用于下寒武统生物地层学的形态种（form-species）。此外，Skiagia各物种间存在细微的形态差异……