The macro‐ and microfossil record of the Cambrian priapulid <i>Ottoia</i>

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).

show abstract

“…A; Smith et al . ) though the thinner‐walled basal pad has been secondarily lost from all but a few specimens (e.g. Fig.…”

Section: Small Carbonaceous Fossilsmentioning

confidence: 99%

A cryptic record of Burgess Shale‐type diversity from the early Cambrian of Baltica

et al. 2016

Self Cite

View full text Add to dashboard Cite

show abstract

“…The contribution by Hejnol and co-workers [32] describes the organization of the nervous system in the larva of the penis worm, a member of Priapulida. Priapulida is recognized as an ecdysozoan that is little different from fossil priapulids from Early [33] and Mid-Cambrian Lagerstätten [34], in which traces of a nervous system with ganglion-like arrangements have been identified [35]. Here the authors describe the larval a nervous system using a palette of antisera raised against cytoskeletal proteins and neuropeptides to resolve the early development of a circumstomodeal rstb.royalsocietypublishing.org Phil.…”

Section: Organization and Contributions To This Issuementioning

confidence: 99%

Introduction to ‘Homology and convergence in nervous system evolution’

Strausfeld

Hirth

2016

Phil. Trans. R. Soc. B

View full text Add to dashboard Cite

The origin of brains and central nervous systems (CNSs) is thought to have occurred before the Palaeozoic era 540 Ma. Yet in the absence of tangible evidence, there has been continued debate whether today's brains and nervous systems derive from one ancestral origin or whether similarities among them are due to convergent evolution. With the advent of molecular developmental genetics and genomics, it has become clear that homology is a concept that applies not only to morphologies, but also to genes, developmental processes, as well as to behaviours. Comparative studies in phyla ranging from annelids and arthropods to mammals are providing evidence that corresponding developmental genetic mechanisms act not only in dorso–ventral and anterior–posterior axis specification but also in segmentation, neurogenesis, axogenesis and eye/photoreceptor cell formation that appear to be conserved throughout the animal kingdom. These data are supported by recent studies which identified Mid-Cambrian fossils with preserved soft body parts that present segmental arrangements in brains typical of modern arthropods, and similarly organized brain centres and circuits across phyla that may reflect genealogical correspondence and control similar behavioural manifestations. Moreover, congruence between genetic and geological fossil records support the notion that by the ‘Cambrian explosion’ arthropods and chordates shared similarities in brain and nervous system organization. However, these similarities are strikingly absent in several sister- and outgroups of arthropods and chordates which raises several questions, foremost among them: what kind of natural laws and mechanisms underlie the convergent evolution of such similarities? And, vice versa: what are the selection pressures and genetic mechanisms underlying the possible loss or reduction of brains and CNSs in multiple lineages during the course of evolution? These questions were addressed at a Royal Society meeting to discuss homology and convergence in nervous system evolution. By integrating knowledge ranging from evolutionary theory and palaeontology to comparative developmental genetics and phylogenomics, the meeting covered disparities in nervous system origins as well as correspondences of neural circuit organization and behaviours, all of which allow evidence-based debates for and against the proposition that the nervous systems and brains of animals might derive from a common ancestor.

show abstract

“…Generally, the Cambrian cycloneuralians were preserved mainly either as centimeter-sized flattened forms in the Burgess Shale-type preservation (Conway Morris, 1977;Briggs et al, 1994;Chen, 2004;Hou et al, 2004;Conway Morris and Peel, 2010;Peel, 2010;Erwin and Valentine, 2013), or as millimeter-sized three dimensional forms in the Orsten-type preservation (Bentson and Yue, 1997;Dong et al, 2004Dong et al, , 2005aDong et al, , 2010Maas et al, 2007bMaas et al, , 2009Zhang, X.G. et al, 2011;Liu et al, 2014b), with some minor reports as small carbonaceous fossils (Smith et al, 2015). They have comparatively great individual abundance (Conway Morris, 1979;Zhao et al, 2014) and played an important role in the Cambrian ecosystems (Maas, 2013).…”

Section: Introductionmentioning

confidence: 96%

“…Except for some loriciferan worms (Maas et al, 2007a(Maas et al, , 2009Peel, 2010) and a possible larval roundworm (Maas et al, 2007b), the majority of the cycloneuralian worms might represent at least Cycloneuralia, or even Scalidophora, but an assignment to an in-group taxon is not possible either due to missing data or because they were derivatives of the stem-lineage toward modern forms (Budd, 2001; A c c e p t e d M a n u s c r i p t 3 Shale-type preservation (Butterfield, 2003) guarantees that the worm bodies are completely preserved, but the details, e.g., the morphology and arrangement pattern of the pharyngeal teeth and the introvert scalids, are generally difficult to discern, and the ambiguity of these key features hampers a conclusive phylogenetic assignment ; but see Smith et al, 2015). In contrast, the Orsten-type preservation (Maas et al, 2006) provides excellent details of the cuticular structures in three dimensions, with a maximal resolution of 0.5 µm, as well as the early ontogenetic stages that belong to the same species (Müller, 1985;Müller and Walossek, 1985;Walossek, 1993;Maas et al, 2003Maas et al, , 2006Dong et al, 2005b;Zhang, H.Q.…”

Section: Introductionmentioning

confidence: 99%