Palaeopascichnida is a problematic group of extinct organisms that is globally distributed in Ediacaran sequences of Avalonia, Baltica, Siberia, South China and Australia. The fossils related to Palaeopascichnida consist of serially or cluster-like arranged, millimetre- to centimetre-scale globular or allantoid chambers, which are characterized by substantial differences in preservation, leading to no consistent diagnosis for these organisms. Here we integrate morphometric variation, stratigraphic distribution and habitat settings of more than 1200 specimens from all known fossil localities. The results of the morphological analysis demonstrate variation in chamber shape and size, and allow us to recognize six valid species within the group. Statistical analysis of the specimen distribution with respect to sedimentary environments indicates a significant difference in palaeoecological settings between species, making a significant contribution to the evolution and systematic palaeontology of these problematic organisms and perspective on their use in Neoproterozoic biostratigraphy. Our revision and systematic study sheds new light on one of the least studied groups of the late Ediacaran biota.

The need to re-examine Rangea has been motivated by two factors: first, by the recent progress in the understanding of three-dimensional mouldic preservation of Vendian fossils, and second, by discoveries of this taxon outside Gondwana albeit in the same sedimentary environment as seen in Namibia. Several important features are revealed, including the in situ posture in the sediment, the double-layered quilted structure, the tripartite stemless body and the mucous-supported sheath in the sediment. It is suggested that Rangea represents an infaunal organism, and that the similarity with other members of the Nama-type biota reflects convergence in functional and fabricational constraints in relation to infaunal life habit.

Single grains of detrital white mica from two different synorogenic sediments in the Southern Urals were analysed using the in situ ultraviolet laser ablation Ar–Ar dating technique to discriminate between age signatures associated with a high-pressure signal (phengites) from those related to muscovite only. Two disparately aged sandstone formations of Neoproterozoic (Upper Vendian) and Upper Devonian (Famennian) age were formed by the erosion of high-relief source areas with contemporaneously exhumed high-pressure rocks. A bimodal distribution of ages and chemical compositions can be detected in the two detrital populations. There is no age overlap between the two populations, reflecting completely different source areas containing high-pressure rocks of different ages. Within the Upper Vendian sandstones, detrital white mica from a 571–609 Ma age group is phengitic in composition (Si 3.3–3.41 per formula unit), while an older 645–732 Ma age group is comprised of muscovite composition grains only. The first group is compatible with the time of late exhumation and emplacement of a source area containing high-pressure rocks, the Neoproterozoic Beloretzk terrane. The older age range is compatible with a long history of cooling and the allochthonous nature of this terrane. Detrital white mica from the Famennian sandstones (Zilair Formation) comprises one age group (342–421 Ma) containing phengite (Si 3.21–3.39 per formula unit) and muscovite, and a second group (446–496 Ma) containing muscovite only. While the derivation of the second group cannot be correlated with any as yet known regional data, the first age group indicates the earliest arrival of high-pressure rocks at the surface along the suture zone after Late Devonian arc–continent collision.