New fossil assemblages from the Early Ordovician Fezouata Biota

Abstract The Fezouata Biota (Morocco) is an exceptionally well-preserved fossil community of Early Ordovician age and although its oldest units are comparable with Burgess Shale-type localities of the Cambrian Explosion, little attention has been paid to the younger units despite potential to reveal the conditions of the Ordovician Radiation. Herein, we describe a new middle to upper Floian Fezouata locality (Taichoute) encompassing an assemblage dominated by large bivalved euarthropods and giant filter-feeding radiodonts, which were transported and preserved in concretions associated with density-flow deposits. Taichoute captures the closing of the taphonomic window that characterizes exceptional fossil preservation during the Cambrian Explosion (i.e., carbonaceous compressions) as well as the faunal transition to assemblages dominated by typical Palaeozoic taxa.

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Burgess Shale-type Preservation and its Distribution in Space and Time

The Paleontological Society Papers ◽

10.1017/s1089332600002837 ◽

2014 ◽

Vol 20 ◽

pp. 123-146 ◽

Cited By ~ 37

Author(s):

Robert R. Gaines

Keyword(s):

Soft Tissues ◽

Cambrian Explosion ◽

Burgess Shale ◽

Seawater Chemistry ◽

Middle Cambrian ◽

Space And Time ◽

Fossil Assemblages ◽

Type Preservation ◽

Diagenetic Environment

Burgess Shale-type fossil assemblages provide a unique record of animal life in the immediate aftermath of the so-called “Cambrian explosion.” While most soft-bodied faunas in the rock record were conserved by mineral replication of soft tissues, Burgess Shale-type preservation involved the conservation of whole assemblages of soft-bodied animals as primary carbonaceous remains, often preserved in extraordinary anatomical detail. Burgess Shale-type preservation resulted from a combination of influences operating at both local and global scales that acted to drastically slow microbial degradation in the early burial environment, resulting in incomplete decomposition and the conservation of soft-bodied animals, many of which are otherwise unknown from the fossil record. While Burgess Shale-type fossil assemblages are primarily restricted to early and middle Cambrian strata (Series 2–3), their anomalous preservation is a pervasive phenomenon that occurs widely in mudstone successions deposited on multiple paleocontinents. Herein, circumstances that led to the preservation of Burgess Shale-type fossils in Cambrian strata worldwide are reviewed. A three-tiered rank classification of the more than 50 Burgess Shale-type deposits now known is proposed and is used to consider the hierarchy of controls that regulated the operation of Burgess Shale-type preservation in space and time, ultimately determining the total number of preserved taxa and the fidelity of preservation in each deposit. While Burgess Shale-type preservation is a unique taphonomic mode that ultimately was regulated by the influence of global seawater chemistry upon the early diagenetic environment, physical depositional (biostratinomic) controls are shown to have been critical in determining the total number of taxa preserved in fossil assemblages, and hence, in regulating many of the important differences among Burgess Shale-type deposits.

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Extraordinary fossils reveal the nature of Cambrian life: a commentary on Whittington (1975) ‘The enigmatic animal Opabinia regalis , Middle Cambrian, Burgess Shale, British Columbia’

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2014.0313 ◽

2015 ◽

Vol 370 (1666) ◽

pp. 20140313 ◽

Cited By ~ 5

Author(s):

Derek E. G. Briggs

Keyword(s):

British Columbia ◽

Royal Society ◽

Early Evolution ◽

Cambrian Explosion ◽

Burgess Shale ◽

Critical Interval ◽

Middle Cambrian ◽

Early Ordovician ◽

History Of ◽

350Th Anniversary

Harry Whittington's 1975 monograph on Opabinia was the first to highlight how some of the Burgess Shale animals differ markedly from those that populate today's oceans. Categorized by Stephen J. Gould as a ‘weird wonder’ ( Wonderful life , 1989) Opabinia , together with other unusual Burgess Shale fossils, stimulated ongoing debates about the early evolution of the major animal groups and the nature of the Cambrian explosion. The subsequent discovery of a number of other exceptionally preserved fossil faunas of Cambrian and early Ordovician age has significantly augmented the information available on this critical interval in the history of life. Although Opabinia initially defied assignment to any group of modern animals, it is now interpreted as lying below anomalocaridids on the stem leading to the living arthropods. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society .

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A new Late Silurian (Pridolian) naraoiid (Euarthropoda: Nektaspida) from the Bertie Formation of southern Ontario, Canada—delayed fallout from the Cambrian explosion

Journal of Paleontology ◽

10.1017/s0022336000043948 ◽

2004 ◽

Vol 78 (6) ◽

pp. 1138-1145 ◽

Cited By ~ 10

Author(s):

Jean-Bernard Caron ◽

David M. Rudkin ◽

Stuart Milliken

Keyword(s):

Late Ordovician ◽

Cambrian Explosion ◽

Burgess Shale ◽

Soft Bottom ◽

Southern Ontario ◽

Middle Cambrian ◽

Holotype Specimen ◽

Extinction Events ◽

Lazarus Effect ◽

Mass Extinction Events

The discovery of a new naraoiid nektaspid in the Upper Silurian (Pridolian) of southeastern Ontario significantly extends the range of this unusual group. Nektaspids are nonmineralized arthropods typical of Early and Middle Cambrian soft-bottom communities, but were thought to have become extinct in the Late Ordovician. The unique holotype specimen of Naraoia bertiensis n. sp. comes from a Konservat–Lagerstätte deposit renowned for its eurypterid fauna (the Williamsville Member of the Bertie Formation). Naraoia bertiensis lacks thoracic segments and is morphologically similar to Naraoia compacta from the Middle Cambrian Burgess Shale, save for the presence of a long ventral cephalic doublure and a subtly pointed posterior shield. To examine the phylogenetic relationships of the new naraoiid, we coded characters of the holotype specimen and of nine previously described nektaspids. The results confirm a sister taxon relationship between Naraoia compacta and Naraoia bertiensis and the monophyly of nektaspid forms lacking thoracic segments (family Naraoiidae). This latter group may have arisen from an ancestral segment-bearing form through heterochronic loss of thoracic segments early in the Cambrian. The disjunct occurrence of a naraoiid nektaspid in the Late Silurian resembles the reappearance of other “Lazarus taxa” that were thought to have been eliminated during mass extinction events. The naraoiid lineage survived the Late Ordovician biotic crisis, but in this case the “Lazarus effect” seems likely to be taphonomic in origin.

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Chance, Evolution, and the Metaphysical Implications of Paleontological Practice

10.1007/978-3-030-75797-7_7 ◽

2021 ◽

pp. 119-143

Author(s):

Alan C. Love

Keyword(s):

Evolutionary Process ◽

Cambrian Explosion ◽

Burgess Shale ◽

Stephen Jay Gould ◽

History Of

AbstractFor several decades, a debate has been waged over how to interpret the significance of fossils from the Burgess Shale and Cambrian Explosion. Stephen Jay Gould argued that if the “tape of life” was rerun, then the resulting lineages would differ radically from what we find today, implying that humans are a happy accident of evolution. Simon Conway Morris argued that if the “tape of life” was rerun, the resulting lineages would be similar to what we now observe, implying that intelligence would still emerge from an evolutionary process. Recent methodological innovations in paleontological practice call into question both positions and suggest that global claims about the history of life, whether in terms of essential contingency or predictable convergence, are unwarranted.

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Early fossil record of Euarthropoda and the Cambrian Explosion

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1719962115 ◽

2018 ◽

Vol 115 (21) ◽

pp. 5323-5331 ◽

Cited By ~ 34

Author(s):

Allison C. Daley ◽

Jonathan B. Antcliffe ◽

Harriet B. Drage ◽

Stephen Pates

Keyword(s):

Fossil Record ◽

Trace Fossils ◽

Cambrian Explosion ◽

Burgess Shale ◽

Crown Group ◽

Total Group ◽

Stem Lineage ◽

Coherent Picture ◽

Insight Into ◽

Phosphate Deposits

Euarthropoda is one of the best-preserved fossil animal groups and has been the most diverse animal phylum for over 500 million years. Fossil Konservat-Lagerstätten, such as Burgess Shale-type deposits (BSTs), show the evolution of the euarthropod stem lineage during the Cambrian from 518 million years ago (Ma). The stem lineage includes nonbiomineralized groups, such as Radiodonta (e.g., Anomalocaris) that provide insight into the step-by-step construction of euarthropod morphology, including the exoskeleton, biramous limbs, segmentation, and cephalic structures. Trilobites are crown group euarthropods that appear in the fossil record at 521 Ma, before the stem lineage fossils, implying a ghost lineage that needs to be constrained. These constraints come from the trace fossil record, which show the first evidence for total group Euarthropoda (e.g., Cruziana, Rusophycus) at around 537 Ma. A deep Precambrian root to the euarthropod evolutionary lineage is disproven by a comparison of Ediacaran and Cambrian lagerstätten. BSTs from the latest Ediacaran Period (e.g., Miaohe biota, 550 Ma) are abundantly fossiliferous with algae but completely lack animals, which are also missing from other Ediacaran windows, such as phosphate deposits (e.g., Doushantuo, 560 Ma). This constrains the appearance of the euarthropod stem lineage to no older than 550 Ma. While each of the major types of fossil evidence (BSTs, trace fossils, and biomineralized preservation) have their limitations and are incomplete in different ways, when taken together they allow a coherent picture to emerge of the origin and subsequent radiation of total group Euarthropoda during the Cambrian.

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Using experimental decay of modern forms to reconstruct the early evolution and morphology of fossil enteropneusts

Paleobiology ◽

10.1017/pab.2015.11 ◽

2015 ◽

Vol 41 (3) ◽

pp. 460-478 ◽

Cited By ~ 14

Author(s):

Karma Nanglu ◽

Jean-Bernard Caron ◽

Christopher B. Cameron

Keyword(s):

Fossil Record ◽

Morphological Characters ◽

Early Diagenesis ◽

Body Plan ◽

Morphological Features ◽

Laboratory Setting ◽

Burgess Shale ◽

Comprehensive Understanding ◽

Fossil Preservation ◽

Experimental Decay

AbstractDecay experiments are becoming a more widespread tool in evaluating the fidelity of the fossil record. Character interpretations of fossil specimens stand to benefit from an understanding of how decay can result in changes in morphology and, potentially, total character loss. We performed a decay experiment for the Class Enteropneusta to test the validity of anatomical interpretations of the Burgess Shale enteropneust Spartobranchus tenuis and to determine how the preservation of morphological features compares with the sequence of character decay in extant analogues. We used three species of enteropneust (Saccoglossus pusillus, Harrimania planktophilus, and Balanoglossus occidentalis) representing the two major families of Enteropneusta. Comparisons between decay sequences suggest that morphological characters decay in a consistent and predictable manner within Enteropneusta, and do not support the hypothesis of stemward slippage. The gill bars and nuchal skeleton were the most decay resistant, whereas the gill pores and pre-oral ciliary organ were unequivocally the most decay prone. Decay patterns support the identification of the nuchal skeleton, gill bars, esophageal organ, trunk, and proboscis in Spartobranchus tenuis and corroborate a harrimaniid affinity. Bias due to the taphonomic loss of taxonomically informative characters is unlikely. The morphologically simple harrimaniid body plan can be seen, therefore, to be plesiomorphic within the enteropneusts. Discrepancies between the sequence of decay in a laboratory setting and fossil preservation also exist. These discrepancies are highlighted not to discredit the use of modern decay studies but rather to underline their non-actualistic nature. Paleoenvironmental variables besides decay, such as the timeframe between death and early diagenesis as well as postmortem transport, are discussed relative to decay data. These experiments reinforce the strength of a comprehensive understanding of decay sequences as a benchmark against which to describe fossil taxa and understand the conditions leading to fossilization.

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Burgess Shale-type faunas in the context of the ‘Cambrian explosion’: a review

Journal of the Geological Society ◽

10.1144/gsjgs.149.4.0631 ◽

1992 ◽

Vol 149 (4) ◽

pp. 631-636 ◽

Cited By ~ 32

Author(s):

S. CONWAY MORRIS

Keyword(s):

Cambrian Explosion ◽

Burgess Shale

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A giant nektobenthic radiodont from the Burgess Shale and the significance of hurdiid carapace diversity

Royal Society Open Science ◽

10.1098/rsos.210664 ◽

2021 ◽

Vol 8 (9) ◽

pp. 210664

Author(s):

J.-B. Caron ◽

J. Moysiuk

Keyword(s):

Trophic Ecology ◽

Cambrian Explosion ◽

Ecological Niches ◽

Burgess Shale ◽

Apex Predators ◽

Geometric Morphometric ◽

Bedding Planes ◽

Large Predators ◽

Benthic Resources ◽

High Diversity

Radiodonts, stem-group euarthropods that evolved during the Cambrian explosion, were among the largest and most diversified lower palaeozoic predators. These animals were widespread geographically, occupying a variety of ecological niches, from benthic foragers to nektonic suspension feeders and apex predators. Here, we describe the largest Cambrian hurdiid radiodont known so far, Titanokorys gainesi , gen. et sp. nov., from the Burgess Shale (Marble Canyon, Kootenay National Park, British Columbia). Estimated to reach half a metre in length, this new species bears a very large ovoid-shaped central carapace with distinct short posterolateral processes and an anterior spine. Geometric morphometric analyses highlight the high diversity of carapace shapes in hurdiids and show that Titanokorys bridges a morphological gap between forms with long and short carapaces. Carapace shape, however, is prone to homoplasy and shows no consistent relationship with trophic ecology, as demonstrated by new data, including a reappraisal of the poorly known Pahvantia . Despite distinct carapaces, Titanokorys shares similar rake-like appendages for sediment-sifting with Cambroraster, a smaller but much more abundant sympatric hurdiid from the Burgess Shale . The co-occurrence of these two species on the same bedding planes highlights potential competition for benthic resources and the high diversity of large predators sustained by Cambrian communities.

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