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

Slater, Ben J.; Harvey, Thomas H. P.; Guilbaud, Romain; Butterfield, Nicholas J.

doi:10.1111/pala.12273

Cited by 43 publications

(54 citation statements)

References 132 publications

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“…3c). In contrast to sparsely fossiliferous mid-shelves, inner-and outer-shelf facies preserved most diverse SCFs assemblages, along with conspicuous burrows and bioturbation fabrics (Slater et al, 2017). These palaeontological data corroborate the geochemical signatures for oxygenated inner-and outer-shelf environments (Fig.…”

Section: Resultssupporting

confidence: 77%

Oxygen minimum zones in the early Cambrian ocean

Guilbaud¹,

Slater²,

Poulton³

et al. 2018

Geochem. Persp. Let.

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The relationship between the evolution of early animal communities and oceanic oxygen levels remains unclear. In particular, uncertainty persists in reconstructions of redox conditions during the pivotal early Cambrian (541-510 million years ago, Ma), where conflicting datasets from deeper marine settings suggest either ocean anoxia or fully oxygenated conditions. By coupling geochemical palaeoredox proxies with a record of organic-walled fossils from exceptionally well-defined successions of the early Cambrian Baltic Basin, we provide evidence for the early establishment of modern-type oxygen minimum zones (OMZs). Both innerand outer-shelf environments were pervasively oxygenated, whereas mid-depth settings were characterised by spatially oscillating anoxia. As such, conflicting redox signatures recovered from individual sites most likely derive from sampling bias, whereby anoxic conditions represent mid-shelf environments with higher productivity. This picture of a spatially restricted anoxic wedge contrasts with prevailing models of globally stratified oceans, offering a more nuanced and realistic account of the Proterozoic-Phanerozoic ocean transition.

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Section: Resultssupporting

confidence: 77%

Oxygen minimum zones in the early Cambrian ocean

Guilbaud¹,

Slater²,

Poulton³

et al. 2018

Geochem. Persp. Let.

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“…The reconstructed origins of the molluscan lineage, for example, have been overhauled in order to accommodate two emblematic Cambrian taxa, Halkieria and Wiwaxia 2–9 . These two genera bear superficially similar sclerites, which occur the world over as carbonaceous and mineralized microfossils 10–13 ; the grouping Sachitida was erected to reflect this perceived commonality 14 . The case for phylogenetic proximity was strengthened by the discovery of articulated specimens in the Burgess Shale and Sirius Passet Lagerstätten , which showed that the sclerites of both taxa were dorsal and imbricating 2,15,16 .…”

Section: Introductionmentioning

confidence: 99%

Orthrozanclus elongata n. sp. and the significance of sclerite-covered taxa for early trochozoan evolution

Zhao

Smith

Yin

et al. 2017

Sci Rep

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Orthrozanclus is a shell-bearing, sclerite covered Cambrian organism of uncertain taxonomic affinity, seemingly representing an intermediate between its fellow problematica Wiwaxia and Halkieria. Attempts to group these slug-like taxa into a single ‘halwaxiid’ clade nevertheless present structural and evolutionary difficulties. Here we report a new species of Orthrozanclus from the early Cambrian Chengjiang Lagerstätte. The scleritome arrangement and constitution in this material corroborates the link between Orthrozanclus and Halkieria, but not with Wiwaxia — and calls into question its purported relationship with molluscs. Instead, the tripartite construction of the halkieriid scleritome finds a more compelling parallel in the camenellan tommotiids, relatives of the brachiopods and phoronids. Such a phylogenetic position would indicate the presence of a scleritome in the common ancestor of the three major trochozoan lineages, Mollusca, Annelida and Brachiozoa. On this view, the absence of fossil Ediacaran sclerites is evidence against any ‘Precambrian prelude’ to the explosive diversification of these phyla in the Cambrian, c. 540–530 million years ago.

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“…This fossil bears a striking resemblance to the SCF chaetae Baltichaeta jormunganda known from younger deposits of the early Cambrian Stage 4 File Haidar Formation of Sweden (compare with Slater et al . , fig. 8, in particular specimen 8E).…”

Section: Small Carbonaceous Fossilsmentioning

confidence: 99%

“…On Baltica, sediments preserving a rich record of SCFs have been discovered from the early Cambrian of Sweden (Slater et al . ; Guilbaud et al . ; Kesidis et al .…”

mentioning

confidence: 99%

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

Slater

Willman

2019

LET

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We describe an assemblage of small carbonaceous fossils (SCFs) and acritarchs from cored siltstones of the Lappajärvi impact structure, west‐central Finland. Previous studies had detected a depauperate acritarch biota ascribed to a deep Proterozoic origin—this age, however, was based on recovery of long‐ranging poorly age‐diagnostic sphaeromorphs. To resolve the age and provenance of these crater sediments, we applied low‐manipulation processing techniques optimized for retrieval of larger organic‐walled microfossils. Our study revealed a previously undetected assemblage containing numerous metazoan SCFs consisting of flattened ‘protoconodonts’ (grasping spines assignable to total group Chaetognatha) and a distinctive fossilised chaeta, possibly representing the oldest known annelid remains. Phylogenetically problematic fossils include various acritarchs (large Leiosphaeridia sp., Tasmanites tenellus, smaller sphaeromorphs, Synsphaeridium, Archaeodiscina and Granomarginata) and filamentous forms (Palaeolyngbya‐ and Rugosoopsis‐like filaments, Siphonophycus), likely representing prokaryotic or protistan grades of organisation. As well as adding new diversity to an emerging SCFs record, these data substantially refine the age of these sediments by more than half a billion years, to an early Cambrian Terreneuvian age. More specifically, the assemblage is equivalent to that of the Lontova Formation from the Baltic States and northwest Russia, but is previously unreported from Finland. Identification of Lontova‐type SCFs/organic‐walled microfossils at Lappajärvi further constrains the poorly resolved extent of maximum flooding during the early Cambrian in Baltica. Renewed attention should be directed to strata that have thus far produced only biostratigraphically long‐ranging or ambiguous palynological assemblages—‘SCF‐style’ processing can reveal hitherto undetected, age‐informative microfossils that are otherwise selectively removed in conventional palynological studies.

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

Cited by 43 publications

References 132 publications

Oxygen minimum zones in the early Cambrian ocean

Oxygen minimum zones in the early Cambrian ocean

Orthrozanclus elongata n. sp. and the significance of sclerite-covered taxa for early trochozoan evolution

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

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