This study presents a paleobiological investigation and systematic taxonomy of early Cambrian calcified cyanobacteria in 10 shallow marine carbonate sections – both reefal and non-reefal – from South China. Our findings provide robust support for the view that cyanobacterial calcification was widespread in shallow marine environments and associated facies during the early Cambrian, defining a major cyanobacterial calcification episode (CCE). 

By combining incubation experiments, microscopy, biomolecular analyses, and spectroscopy to assess the biomacromolecular composition of cyst walls, we show that Selenopemphix and Multispinula represent two distinct cyst-based genera, with different preservation potentials. We emend their diagnoses and describe two new Multispinula species, M. varispinosa sp. nov. and M. robusta sp. nov., in addition to M. quanta. 

In the Marmolance succession (SE Spain), in limestones intercalating marls with planktonic foraminifera, we documented Langhian Nummulites species as well as Serravallian lepidocyclinids and Risananeiza. Papazzoni et al. questioned our results, arguing that the larger benthic foraminifera (LBF) must be reworked. However, the quantitatively defined LBF assemblages are spatially and temporally segregated, which can only be due to in situ accumulation across different facies belts of the carbonate ramp.

Today’s sea-ice-covered Arctic Ocean hosts only one species of calcifying planktonic foraminifera, unlike warmer oceans with diverse communities. Fossils show that other species once inhabited the Arctic, but their identities and environmental significance remain uncertain. Using detailed microscopy and hundreds of shell measurements, we resolve these fossil species and establish a new taxonomic framework providing the foundation for improved reconstructions of Quaternary Arctic climate history.