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

Abstract

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

Early Cambrian small carbonaceous fossils (SCFs) from an impact crater in western Finland

“…in Slater et al . ). Occasional spines of this type have also been reported in acritarch studies from Lontovan sediments under the name of Ceratophyton vernicosum (Volkova et al .…”

“…In comparison with the spines recovered here, flattened carbonaceous Protohertzina from the Lontova Formation can be substantially larger (occasionally exceeding 2.1 mm in length; Slater et al . ). However, this likely reflects the smaller sample size of the present study which is restricted to core material from a single locality – all spines from the Vimpeli‐302 samples fall within the known size range of Protohertzina compressa , and extrapolations of incomplete/broken specimens suggest larger spines of a comparable length were also present among this population.…”

“…Slater et al . () compared a subset of these carbonaceous spines to those found among the grasping apparatus of extant and fossil chaetognaths (McIlroy & Szaniawski , fig. ), and more specifically the SSF taxon Protohertzina , which are widely regarded to be the disarticulated phosphatized (or biophosphatic) grasping spines of early Cambrian total group chaetognaths (Szaniawski , ; Vannier et al .…”

“…These Finnish examples add to the mounting body of evidence for the importance and prevalence of chaetognaths as predators in earliest Cambrian marine ecosystems (Missarzhevsky ; Szaniawski , ; Slater et al . ; see Discussion section for details on the age of this deposit).…”

“…On Baltica, sediments displaying preservation of ‘conventional’ acritarchs akin to those at Lappajärvi have recently been found to yield such larger organic remains, detectable only when low‐manipulation processing techniques are employed (Slater et al . ). This larger class of organic microfossils have been dubbed ‘small carbonaceous fossils’ or ‘SCFs’ (see Butterfield & Harvey ), and remain a relatively underexploited source of palaeobiological and biostratigraphical data, typically encompassing a polyphyletic assortment of metazoan, algal and protistan remains.…”