Was there a Cambrian explosion on land?

土地的殖民是生命历史上的一个关键转折。分子时钟分析表明，早古生代陆地上的节肢动物和植物发生了快速辐射，与寒武纪的海洋大爆炸重叠，但化石记录令人沮丧地有限。该项目将结合古生物学和计算方法来弥补化石记录中的这一差距，并为陆地生态系统的进化建立一个时间表。早古生代陆相沉积将使用低操纵性的酸提取程序来分离小型碳质化石(SCF)。SCF是很少化石化的小型生物的独特保存窗口。20世纪80年代和90年代，人们曾报道过来自外星沉积的节肢动物干细胞因子，但自那以后一直被忽视。对煤球的初步分析表明，特殊的SCF适合与现存和古生代的类群进行比较。将使用地球化学技术测试有问题的SCF的系统发育位置和非海洋来源，为识别最古老的陆地生态系统提供可靠的标准。SCF的记录将通过使用断层扫描修改博物馆藏品中Rhynie硅质岩和Mazon Creek生物群的节肢动物来补充。这些化石证据将为新的陆系化时间表提供一套可靠的校准，这反过来将成为检验有关陆地生物多样化驱动因素的假说的支柱。

The colonisation of land was a key transition in the history of life. Molecular clock analyses imply a rapid radiation ofarthropods and plants on land in the early Palaeozoic, overlapping with the Cambrian explosion in the sea, but the fossilrecord is frustratingly limited. The project will combine palaeontological and computational methods to bridge this gap inthe fossil record and establish a timescale for the evolution of terrestrial ecosystems. Early Palaeozoic terrestrial depositswill be investigated using a low-manipulation acid extraction procedure to isolate small carbonaceous fossils (SCFs).SCFs are a unique preservation window for small organisms that rarely fossilise. Arthropod SCFs from numerousterrestrial deposits have been reported in the 1980 and 1990s but have been overlooked since. Preliminary analyses ofcoal balls reveal exceptional SCFs suitable for comparison with extant and Palaeozoic taxa. The phylogenetic positionand non-marine origin of problematic SCFs will be tested using geochemical techniques, providing reliable criteria forrecognising the oldest terrestrial ecosystems. The SCF record will be complemented by revising arthropods from theRhynie chert and Mazon Creek biotas in museum collections using tomography. This fossil evidence will provide a set ofrobust calibrations for a new timescale of terrestrialisation, which will in turn serve as a backbone for testing hypothesesabout the drivers of the diversification of life on land.