Exceptionally preserved 'Burgess Shale-type' fossil assemblages from the Cambrian of Laurentia, South China and Australia record a diverse array of non-biomineralizing organisms. During this time, the palaeocontinent Baltica was geographically isolated from these regions, and is conspicuously lacking in terms of comparable accessible early Cambrian Lagerst€ atten. Here we report a diverse assemblage of small carbonaceous fossils (SCFs) from the early Cambrian (Stage 4) File Haidar Formation of southeast Sweden and surrounding areas of the Baltoscandian Basin, including exceptionally preserved remains of Burgess Shale-type metazoans and other organisms. Recovered SCFs include taxonomically resolvable ecdysozoan elements (priapulid and palaeoscolecid worms), lophotrochozoan elements (annelid chaetae and wiwaxiid sclerites), as well as 'protoconodonts', denticulate feeding structures, and a background of filamentous and spheroidal microbes. The annelids, wiwaxiids and priapulids are the first recorded from the Cambrian of Baltica. The File Haidar SCF assemblage is broadly comparable to those recovered from Cambrian basins in Laurentia and South China, though differences at lower taxonomic levels point to possible environmental or palaeogeographical controls on taxon ranges. These data reveal a fundamentally expanded picture of early Cambrian diversity on Baltica, and provide key insights into high-latitude Cambrian faunas and patterns of SCF preservation. We establish three new taxa based on large populations of distinctive SCFs: Baltiscalida njorda gen. et sp. nov. (a priapulid), Baltichaeta jormunganda gen. et sp. nov. (an annelid) and Baltinema rana gen. et sp. nov. (a filamentous problematicum).
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.
The fossilized traces of burrowing worms have taken on a considerable importance in studies of the Cambrian explosion, partly because of their use in defining the base of the Cambrian. Foremost among these are the treptichnids, a group of relatively large open probing burrows that have sometimes been assigned to the activities of priapulid scalidophoran worms. Nevertheless, most Cambrian burrows have an uncertain progenitor. Here we report a suite of exceptionally preserved trace and body fossils from sandstones of the lower Cambrian (Stage 4) File Haidar Formation of southern Sweden that can unequivocally be assigned to a scalidophoran producer. We further present the first burrow casts produced via actualistic experiments on living priapulids, and demonstrate the remarkable morphological parallels between these modern and Cambrian fossil equivalents. In addition, co-occurrence of scalidophoran-derived cuticular remains permits a unique synthesis of evidence from trace fossil, body and organic remains. Comparative analysis of these exceptionally preserved fossils supports a scalidophoran producer for treptichnids and by extension suggests a latest Ediacaran origin of the ecdysozoan clade.
The Sirius Passet Lagerstätte of North Greenland is one of the oldest records of soft‐bodied metazoan‐dominated ecosystems from the early Cambrian. The Lagerstätte site itself is restricted to just a single c. 1‐km‐long outcrop located offshore from the shelf margin, in an area affected by metamorphic alteration during the Ellesmerian Orogeny (Devonian – Early Carboniferous). The recent recovery of small carbonaceous fossils (SCFs) to the south, in areas that escaped the effects of this deformation, has substantially expanded the known coverage of organic preservation into shallower water depositional settings in this region. Here, we describe additional SCF assemblages from the siliciclastic shelf succession of the Buen Formation (Cambrian Series 2, stages 3–4; c. 515 Ma), expanding the previously documented SCF biota. Newly recovered material indicates a rich diversity of non‐mineralizing metazoans, chiefly represented by arthropod remains. These include the filtering and grinding elements of a sophisticated crustacean feeding apparatus (the oldest crustacean remains reported to date), alongside an assortment of bradoriid sclerites, including almost complete, 3D valves, which tie together a number of SCFs previously found in isolation. Other metazoan remains include various trilobite cuticles, diverse scalidophoran sclerites, and a range of metazoan fragments of uncertain affinity. This shallower water assemblage differs substantially from the Sirius Passet biota, which is dominated by problematic euarthropod stem‐group members and sponges. Although some of these discrepancies are attributable to taphonomic or temporal factors, these lateral variations in taxonomic composition also point to significant palaeoenvironmental and/or palaeoecological controls on early Cambrian metazoan communities.
The landscapes and seascapes of Earth's surface provide the theatre for life, but to what 12 extent did the actors build the stage? The role of life in the long-term shaping of the 13 planetary surface needs to be understood to ascertain whether Earth is singular among known 14 rocky planets, and to frame predictions of future changes to the biosphere. Modern 15 geomorphic observations and modelling have made strides in this respect, but an under-16 utilized lens through which to interrogate these questions resides in the most complete 17 tangible record of our planetary history: the sedimentary-stratigraphic record (SSR). The 18 characteristics of the SSR have been frequently explained with reference to changes in 19 boundary conditions such as relative sea level, climate, and tectonics. Yet despite the fact that 20 the long-term accrual of the SSR was contemporaneous with the evolution of almost all 21 domains of life on Earth, causal explanations related to biological activity have often been 22 overlooked, particularly within siliciclastic strata. This paper explores evidence for the ways 23 in which organisms have influenced the SSR throughout Earth history and emphasizes that 24 further investigation can help lead us towards a mechanistic understanding of how the 2 25 planetary surface has co-evolved with life. The practicality of discerning life signatures in 26 the SSR is discussed by: 1) distinguishing biologically-dependent versus biologically-27 influenced sedimentary signatures; 2) emphasizing the importance of determining relative 28 time-length scales of processes and demonstrating how different focal lengths of observation 29 (individual geological outcrops and the complete SSR) can reveal different insights; and 3) 30 promoting an awareness of issues of equifinality and underdetermination that may hinder the 31 recognition of life signatures. Multiple instances of life signatures and their historic range 32 within the SSR are reviewed, with examples covering siliciclastic, biogenic and chemogenic 33 strata, and trigger organisms from across the spectrum of Earth's extant and ancient life. 34 With this novel perspective, the SSR is recognised as a dynamic archive that expands and 35 complements the fossil and geochemical records that it hosts, rather than simply being a 36 passive repository for them. The SSR is shown to be both the record and the result of long-37 term evolutionary synchrony between life and planetary surface processes. 38 42 precipitation from solution. Where it is tractable, in exposed outcrop, cores or seismic 43 sections, the SSR has immense value as a record of ancient surface processes. It is the 44 primary repository of deep time geochemical and fossil evidence, and the only tangible 45
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