A hidden record of early animal evolution? Exploring the Cambrian diversity of acritarchs and small carbonaceous fossils.

概述：微化石提供了早期动物进化和随之而来的生态系统重构的丰富记录。这个项目将专注于保存异常完好的原始化石和小型碳质化石(SCF)，以达到对动物如何在大约5亿年前寒武纪进化爆炸期间戏剧性地改变生物圈的新理解。该项目旨在区分动物和非动物微化石，并限制它们的生物亲缘关系、生命模式以及在空间和时间上的分布。这一结果将为地球历史上一个关键时期的多样性和生态变化带来关键的洞察。原始体是亲和力未知的有机壁微化石，使用标准的孢粉实验室技术提取。相比之下，更温和的程序产生更大、更精细的SCF，代表一系列生物体，包括各种动物。尽管有这种分类，但这两个数据集是重叠的。最近，我们已经开始探索一种联合的方法，它有望阐明Acritstras和SCF的亲缘关系和意义，加强它们在古生物学、地层学和古代生态系统中的关键问题上的应用。该项目最初将专注于加拿大纽芬兰Forteau组(寒武纪第四阶段，约5.1亿年前)保存极为完好的尖晶石和SCF。数以百计的超临界流体和数以千计的原料药已经准备好放在玻片上进行分析。根据SCF，一些孢子形体明显来自动物，包括节肢动物、无头类蠕虫和鼻涕状的威瓦夏。其他的仍然是个谜，比如被称为Ceratophyton和Corollasphaeridium的圆锥形原生动物，它们可能代表动物，也可能代表原生生物。同时，超临界流体处理会产生团块、关节排列，甚至是充满细菌原基的粪便颗粒，限制了它们的生物学解释。因此，Forteau的材料提供了一个无与伦比的机会来解决原本神秘的寒武纪微化石的亲缘关系和生态问题。然后，任何见解都可以被更广泛地应用，以帮助限制寒武纪“爆炸”的最大规模的模式和过程。例如，动物来源的微型化石是否可以追溯到埃迪卡拉纪？浮游生物能告诉我们浮游生物的结构吗？生态系统如何应对进化中的重大事件？图1：下寒武统微体化石精选，每个微化石大小约为20至40微米；它们包括两个带刺的原基，以及圆锥形和尖端刺状化石，可能代表单细胞原生生物或动物身体部位。

Overview: Microfossils offer a rich record of early animal evolution and the attendant reconfiguring of ecosystems. This project will focus on exceptionally well-preserved acritarchs and small carbonaceous fossils (SCFs) to reach a new understanding of how animals dramatically changed the biosphere around half a billion years ago, in the Cambrian evolutionary 'explosion'. The project aims to discriminate between animal- and non-animal microfossils, and constrain their biological affinities, modes of life, and distributions in space and time. The results will bring key insights into changes in diversity and ecology through a pivotal interval in Earth history.Acritarchs are organic-walled microfossils of unknown affinity, extracted using standard palynological laboratory techniques. In contrast, more gentle procedures yield larger, more delicate SCFs that represent a range of organisms, including a diversity of animals. Despite this categorization, the two datasets overlap. Recently, we have begun to explore a combined approach, which promises to shed light on the affinities and significance of both acritarchs and SCFs, enhancing their application to key questions in palaeobiology, stratigraphy, and ancient ecosystems. The project will focus initially on exceptionally well-preserved acritarchs and SCFs from the Forteau Formation of Newfoundland, Canada (Cambrian Stage 4, c. 510 million years ago). Hundreds of SCFs and thousands of acritarchs have already been prepared onto glass slides for analysis. In light of the SCFs, some palynomorphs are clearly derived from animals including arthropods, priapulid worms, and the slug-like Wiwaxia. Others remain enigmatic, such as the conical acritarchs known as Ceratophyton and Corollasphaeridium, which could represent animals or perhaps protists. At the same time, SCF-processing yields clumps, articulated arrays, and even faecal-pellets full of acritarchs, constraining their biological interpretation. Therefore, the Forteau material offers an unrivalled opportunity to resolve the affinities and ecologies of otherwise mysterious Cambrian microfossils. Any insights can then be applied more widely to help constrain the largest-scale patterns and processes of the Cambrian 'explosion'. For example, do animal-derived microfossils extend back into the Ediacaran? Can acritarchs tell us about the structure of the plankton? And how did ecosystems respond to major events in evolution? Figure 1: Selection of lower Cambrian microfossils, each measuring around 20 to 40 microns in size; they include two spiny acritarchs alongside conical and spine-tipped forms that could represent unicellular protists or animal body parts.