In this study, a new assemblage of  Ediacaran metazoan fossils is reported from the basal Stáhpogieddi Formation on the Digermulen Peninsula of Arctic Norway, including Anulitubus n. gen. Moczydłowska in Moczydłowska et al., Anulitubus formosus n. gen. n. sp. Moczydłowska in Moczydłowska et al., Coniculus n. gen. Moczydłowska in Moczydłowska et al., Coniculus elegantis n. gen. n. sp. Moczydłowska in Moczydłowska et al., Fistula n. gen. Moczydłowska in Moczydłowska et al., Fistula crenulata n. gen. n. sp. Moczydłowska in Moczydłowska et al. The specimens are three-dimensionally preserved and include tubular and conical skeletons that are morphologically distinguished by their body wall constructions, radial symmetry, polarity, segmentation, and annulation. The skeletons are interpreted to be biomineralized by primary silica based on computed micro-tomographic, petrographic, geochemical and spectroscopic evidence of originally rigid body wall with layers of constant thicknesses, composed of opal, microcrystalline quartz and admixture of carbonaceous material, which differ from the host sediment mineralogy and do not show replacement or encrustation. The fossil-bearing interval immediately overlies strata of Gaskiers age and can be bracketed within 580–541 Ma, but it is estimated to be ~575 Ma on the basis of averaged sedimentation rates and biostratigraphic correlations with Ediacaran biota found in up-section deposits of ~558–555 Ma. Future new findings of such fossils in different preservation modes and further multi-collector inductively coupled plasma mass spectrometry, which shows the silicon fractionation and trace its biogenic origin vs inorganic mineralization, may corroborate the interpretation of biogenic silicification of these earliest skeletal fossils.

The fossils were studied under a reflected light microscope (RLM), a transmitted andpolarized light microscope (PLM), an environmental scanning-transmission electron microscope (STEM) equipped with energy-dispersive X-ray detector for energy dispersive spectroscopy (STEM EDS), and a field emission electron probe microanalyzer (EMP) also equipped with EDS detector. Three-dimensional rendering and visualization of internal structures was also undertaken using a Nikon H225 ST Micro-Computed Tomography (CT) at the University of Oslo (Supplementary Data). Petrographic thin-sectioning was also carried out with geochemical and acid tests, as well as STEM EDS, EMP EDS, and Laser-Raman spectroscopy to determine mineralization (Supplementary Data). The mineral composition of the surrounding mudstone matrix was examined using Laser-Raman spectroscopy and X-ray diffraction (XRD; Supplementary Data).