The Ediacaran–Cambrian (E-C) transition (∼542–517 Ma) witnessed the rapid evolution of Cambrian animals, which was accompanied by carbon cycling anomalies and a significant increase in the concentration of oxygen in Earth’s atmosphere. The mechanisms stimulating the evolution of complex eukaryotes, however, remain problematic, especially concerning the link between biological evolution and contemporaneous changes in the oceanic environment. In this study, integrated δ13Ccarb–δ13Corg–δ15N compositions were analysed from the YD-4 core samples to understand redox fluctuations and nitrogen cycling of the middle Yangtze Block across the E-C transition. Two negative δ13Ccarb excursions (N1 and N2) and a positive δ13Ccarb excursion (P1) are identified from the studied samples and are supposedly of primary origin. Constrained by of the U-Pb age, biolithology and pattern of isotopic variation, N1, P1 and N2 are comparable to the Basal Cambrian Carbon Isotope Excursion (BACE), Zhujiaqing Carbon Isotope Excursion (ZHUCE) and Shiyantou Carbon Isotope Excursion (SHICE). We interpreted the decreased δ15N values in this study as resulting from intensified atmospheric nitrogen fixation driven by enhanced denitrification associated with expanded marine anoxia, as well as partial ammonium assimilation, while increased δ15N values suggest weakened denitrification associated with an amplified oxic water mass. The temporal coincidence of N1 and N2, with two episodes of negative δ15N excursions, and of P1, with a positive δ15N excursion, suggests that variable oceanic redox conditions and nitrogen bioavailability may have influenced the evolution of the Cambrian eukaryote-dominated community.

The relative timing of extinctions and originations is a foundation for reconstructing evolutionary causes. However, there has been a tendency to dismiss reported Ediacaran holdovers in favour of effective extinction around the Cambrian boundary. Here, focusing on the classically Ediacaran frondose biota (Petalonamae), I suggest four main reasons why proposed Ediacaran survivors have previously been denied the acceptance they deserve: denials based on mistaken identity, doppelgängers, a last gasp or dead clades walking. I then point to the lower Cambrian species Stromatoveris psygmoglena as a key example which simultaneously meets these objections. Collectively, Cambrian survivors are a ‘smoking gun’ showing that extinction of the classically Ediacaran frondose biota did not occur until at least 30 Ma after the end of the Ediacaran period, registered by phylogenetic petalonamid Thaumaptilon from the Burgess Shale. Therefore, to paraphrase Mark Twain, reports of their earlier demise have been greatly exaggerated. Causes of their ultimate extinction should instead be sought in their total range and diversity dynamics. Overall, the Ediacaran–Cambrian transition shows extremely low numbers of recorded survivors, but diversity dynamics are dominated by the Cambrian explosion. In this context, recorded occurrences for the classically Ediacaran frondose biota are compatible with at least two extinction events, one within a possible mass extinction near the Cambrian boundary, and later, their ultimate extinction in, or after, the middle Cambrian (Miaolingian Series, Wuliuan Stage). There is, however, no correlative basis for a causal link between the Cambrian transition and the effective or final demise of the classically Ediacaran soft-bodied biota.

Radiodonts are a diverse clade of Lower Palaeozoic stem-group euarthropods that played a key role in the emergence of complex marine trophic webs. The latest addition to the group, Cambroraster falcatus, was recently described from the Wuliuan Burgess Shale, and is characterized by a unique horseshoe-shaped central carapace element. Here we report the discovery of Cambroraster sp. nov. A, a new species from the Cambrian Stage 3 Chengjiang Lagerstätte of South China. The new occurrence of Cambroraster demonstrates that some of the earliest known radiodonts had already evolved a highly derived carapace morphology adapted to an essentially eudemersal life as sediment foragers.

A review of biodiversity curves of marine organisms indicates that, despite fluctuations in amplitude (some large), a large-scale, long-term radiation of life took place during the early Palaeozoic Era; it was aggregated by a succession of more discrete and regionalized radiations across geographies and within phylogenies. This major biodiversification within the marine biosphere started during late Precambrian time and was only finally interrupted in the Devonian Period. It includes both the Cambrian Explosion and the Great Ordovician Biodiversification Event. The establishment of modern marine ecosystems took place during a continuous chronology of the successive establishment of organisms and their ecological communities, developed during the ‘Cambrian substrate revolution’, the ‘Ordovician plankton revolution’, the ‘Ordovician substrate revolution’, the ‘Ordovician bioerosion revolution’ and the ‘Devonian nekton revolution’. At smaller scales, different regional but important radiations can be recognized geographically and some of them have been identified and named (e.g. those associated with the ‘Richmondian Invasion’ during Late Ordovician time in Laurentia and the contemporaneous ‘Boda event’ in parts of Europe and North Africa), in particular from areas that were in or moved towards lower latitudes, allowing high levels of speciation on epicontintental seas during these intervals. The datasets remain incomplete for many other geographical areas, but also for particular time intervals (e.g. during the late Cambrian ‘Furongian Gap’). The early Palaeozoic biodiversification therefore appears to be a long-term process, modulated by bursts in significant diversity and intervals of inadequate data, where its progressive character will become increasingly clearer with the availability of more complete datasets, with better global coverage and more advanced analytical techniques.

The transition between the seemingly disparate Ediacaran and Cambrian faunas is both enigmatic and body-fossil poor. The Chapel Island Formation on the Burin Peninsula, Newfoundland, Canada, contains a rich diversity of ichnofossils, providing new insight into the nature of the Ediacaran–Cambrian transition and early Fortunian ecosystems. Five ichnoguilds are recognized within the Treptichnus pedum zone. Ichnologic data are analysed from an ecospace perspective, revealing a more protracted transition between Ediacaran and Cambrian ecosystems. Our analysis documents the appearance of limbs, vertical burrows and uncontroversial equilibrium structures, as well as the retention of ‘other’ feeding styles, such as microbial grazing and chemosynthesis.

Material previously referred to as Cassubia infercambriensis was re-examined and found to represent a composite fossil of a Peytoia-like anomalocaridid frontal appendage and an arthropod of uncertain affinities comparable to some bivalved arthropod taxa. The frontal appendage is referred to the genus Peytoia based on the presence of elongated ventral spines bearing a single row of auxiliary spines. As well as representing the oldest example of an anomalocaridid in the fossil record (Series 2, Stage 3), Peytoia infercambriensis is also the only record of this group from the East European Craton, therefore extending both the temporal and geographic range of the anomalocaridid family Hurdiidae.

The robust spines and sclerites of the early to middle Cambrian ‘mollusc’ Wiwaxia are ubiquitous in suitably preserved deposits, but are strikingly absent from the Chengjiang Lagerstätte (Cambrian Stage 3, Yunnan Province, SW China). Here we provide the first record of Wiwaxia sclerites from this rich deposit, extending the record of the genus to the earliest Cambrian Series 2. This reinforces the cosmopolitan distribution of this iconic Cambrian lophotrochozoan and demonstrates the strong faunal continuity that unites distant Cambrian Lagerstätten.

Although Banffia constricta was first described in 1911, the affinities of this soft-bodied fossil animal have remained unclear. Banffia is redescribed here, on the basis of over 300 specimens. Banffia has a bipartite body measuring up to 10 cm in length. The entire body is axially twisted along a spiral, clockwise as seen from the front. The anterior section consists of two fused carapace-like units with a prominent crown-like structure at the anterior end surrounding the mouth. This crown-like structure is composed of three concentric circlets. A single antenniform outgrowth lies posterior to the mouth. The posterior section of Banffia is composed of 40 to 50 lightly sclerotised segments. The anus is terminal, and situated in a caudal notch. The gut is straight. Simple serially repeated structures along the gut may represent metameric mid-gut diverticulae. Banffia is considered to have been an epibenthic gregarious animal and possibly a deposit-feeder.

Banffia is putatively classified as an end-member of the phylum Vetulicolia, in a new class, the Banffozoa. If the vetulicolids represent a stem-group deuterostome, the absence of gills and a possible endostyle in Banffia is problematic. The presence of mid-gut diverticulae in Banffia may represent a link with the protostomes.