Small carbonaceous fossils (SCFs) from the Terreneuvian (lower Cambrian) of Baltica

16 Mar 2018

We describe a new assemblage of small carbonaceous fossils (SCFs) from diagenetically 9 minimally altered clays and siltstones of Terreneuvian age from the Lontova and Voosi formations of 10 Estonia, Lithuania and Russia. This is the first detailed account of an SCF assemblage from the 11 Terreneuvian, and includes a number of previously undocumented Cambrian organisms. Recognisably 12 bilaterian-derived SCFs include abundant protoconodonts (total-group Chaetognatha), and distinctive 13 cuticular spines of scalidophoran worms. Alongside these metazoan remains are a range of protistan-14 grade fossils, including Retiranus balticus gen. et sp. nov., a distinctive funnel-shaped or sheet-like 15 problematicum characterized by terminal or marginal vesicles, and Lontohystrichosphaera grandis 16 gen. et sp. nov., a large (100–550 μm) ornamented vesicular microfossil. Together these data offer a 17 fundamentally enriched view of Terreneuvian life in the epicratonic seas of Baltica, from an episode 18 where records of non-biomineralized life are currently sparse. Even so, the recovered assemblages 19 contain a lower diversity of metazoans than SCF biotas from younger (Stage 4) Baltic successions that 20 represent broadly equivalent environments, echoing the diversification signal recorded in the coeval 21 shelly and trace-fossil records. Close comparison to the biostratigraphic signal from Fortunian small 22 shelly fossils (SSFs) supports a late Fortunian age for most of the Lontova/Voosi succession, rather 23 than a younger (wholly Stage 2) range.