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

2014 ◽  
Vol 20 ◽  
pp. 123-146 ◽  
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.

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

2004 ◽  
Vol 78 (6) ◽  
pp. 1138-1145 ◽  
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.

The Burgess Shale arthropod Mollisonia (M. sinica new species): new occurrence from the Middle Cambrian Kaili fauna of southwest China

2002 ◽  
Vol 76 (6) ◽  
pp. 1106-1108 ◽  
Author(s):  
Xingliang Zhang ◽  
Yuanlong Zhao ◽  
Ruidong Yang ◽  
Degan Shu
Keyword(s):  
Southwest China ◽  
Middle Part ◽  
Guizhou Province ◽  
Cambrian Explosion ◽  
Early Cambrian ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Lowermost Part ◽  
Dark Green ◽  
Chengjiang Lagerstätte

The Early Cambrian Chengjiang Lagerstätte, Yunnan Province, Southwest China, has become one of the most celebrated Cambrian fossil Lagerstatten not only for perhaps the earliest biota of soft-bodied organisms in the Phanerozoic (Yuan and Zhao, 1999; Zhang et aI., 2001; but see Budd and Jensen, 2000), but also for a number of significant discoveries (Shu et al., 1996a, 1996b, 1999a, 1999b, 2001), proven to be of particular importance for our understanding the Cambrian explosion. Also in Southwest China, Guizhou Province, there is a very significant, although less acclaimed, Middle Cambrian soft-bodied fauna as well, namely the Kaili fauna, which occurs in the Kaili Formation in Kaili area (Kuizhou). The age of the Kaili Formation ranges from late Early to early Middle Cambrian. Regionally, the Kaili Formation is about 222 m thick and consists of three parts. The lowermost part (late Early Cambrian, about 55 m thick) is dominated by thin, calcareous siltstone strata interbedded with limestone layers at the base. The middle part (early Middle Cambrian, ca. 123 m) consists of dark green mudstone and shale, while the uppermost part (ca. 44 m) is composed of interbedded limestone and silty shale. The Kaili fauna is derived from mudstones in the middle part of the formation (Zhao et aI., 1994; Zhu et aI., 2000).

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

2015 ◽  
Vol 370 (1666) ◽  
pp. 20140313 ◽  
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 .

Nectocaridid ecology, diversity, and affinity: early origin of a cephalopod-like body plan

Paleobiology ◽  
10.1666/12029 ◽  
2013 ◽  
Vol 39 (2) ◽  
pp. 297-321 ◽  
Author(s):  
Martin R. Smith
Keyword(s):  
Body Plan ◽  
Cambrian Explosion ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Low Reynolds Number Flow ◽  
Reynolds Number Flow ◽  
Number Flow ◽  
Early Origin ◽  
First Time ◽  
Cephalopod Evolution

Nectocaridids are soft-bodied early to middle Cambrian organisms known from Burgess Shale-type deposits in Canada, China, and Australia. Originally described as unrelated species, they have recently been interpreted as a clade; their flexible tentacles, camera-type eyes, lateral fins, internal gills, axial cavity, and funnel point to a relationship with the cephalopods. However, aspects of this reinterpretation, including the relevance of the group to cephalopod evolution, have been called into question.Here, I examine new and existing nectocaridid material, including a large new form that may represent a sexual dimorph of Nectocaris pteryx. Differences between existing taxa largely represent taphonomic variation between sites and specimens—which provides further constraint on the organisms' anatomy. I revise the morphology of the tentacles and fins, and describe mouthparts and phosphatized gills for the first time. A mathematical analysis supports the presence of the earliest known camera-type eyes, and fluid mechanical considerations suggest that the funnel is optimized for efficient jet propulsion in a low Reynolds number flow regime.Nectocaridids closely resemble coleoid cephalopods, but a position deeper within Cephalopoda raises fewer stratigraphic challenges. Whether its coleoid-like construction reflects common ancestry or profound convergence, the Nectocaris body plan adds substantially to Cambrian disparity, demonstrating the rapid colonization of nektobenthic niches after the Cambrian explosion.

Burgess Shale-type preservation of both non-mineralizing and ‘shelly’ Cambrian organisms from the Mackenzie Mountains, northwestern Canada

1996 ◽  
Vol 70 (6) ◽  
pp. 893-899 ◽  
Author(s):  
N. J. Butterfield ◽  
C. J. Nicholas
Keyword(s):  
Granular Material ◽  
Surface Texture ◽  
Hydrofluoric Acid ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Small Shelly Fossils ◽  
Polygonal Surface ◽  
Acid Processing ◽  
Mackenzie Mountains ◽  
Type Preservation

Lower to Middle Cambrian shales of the Mount Cap Formation in the Mackenzie Mountains, northwestern Canada, host a variety of Burgess Shale-type macrofossils, including anomalocarid claws, several taxa of bivalved arthropod, articulated hyolithids, and articulated chancelloriids. Hydrofluoric acid processing has also yielded a broad range of organic-walled fossils, most of which are derived from forms more typically known as shelly fossils; e.g., trilobites, inarticulate brachiopods, small shelly fossils (SSF), hyolithids, and chancelloriids. Organic-walled hyolithids include conchs, opercula and helens; the proximal articulation of the helens is erosive, suggesting that they were formed “instantaneously” and periodically replaced. Organic-walled chancelloriid sclerites exhibit a polygonal surface texture and an inner “pith” of dark granular material with distally oriented conoidal divisions; such a pattern is similar to that seen in the fibers of some modern horny sponges and points to a poriferan relationship for the chancelloriids. The robust nature but minimal relief of most of these fossils suggests that primary biomineralization was minimal.

scholarly journals Beyond the Burgess Shale: Cambrian microfossils track the rise and fall of hallucigeniid lobopodians

2013 ◽  
Vol 280 (1767) ◽  
pp. 20131613 ◽  
Author(s):  
Jean-Bernard Caron ◽  
Martin R. Smith ◽  
Thomas H. P. Harvey
Keyword(s):  
Whole Body ◽  
Cambrian Explosion ◽  
Burgess Shale ◽  
Animal Evolution ◽  
Middle Cambrian ◽  
Animal Body ◽  
Cuticular Structures

Burgess Shale-type deposits are renowned for their exquisite preservation of soft-bodied organisms, representing a range of animal body plans that evolved during the Cambrian ‘explosion’. However, the rarity of these fossil deposits makes it difficult to reconstruct the broader-scale distributions of their constituent organisms. By contrast, microscopic skeletal elements represent an extensive chronicle of early animal evolution—but are difficult to interpret in the absence of corresponding whole-body fossils. Here, we provide new observations on the dorsal spines of the Cambrian lobopodian (panarthropod) worm Hallucigenia sparsa from the Burgess Shale (Cambrian Series 3, Stage 5). These exhibit a distinctive scaly microstructure and layered (cone-in-cone) construction that together identify a hitherto enigmatic suite of carbonaceous and phosphatic Cambrian microfossils—including material attributed to Mongolitubulus , Rushtonites and Rhombocorniculum —as spines of Hallucigenia -type lobopodians. Hallucigeniids are thus revealed as an important and widespread component of disparate Cambrian communities from late in the Terreneuvian (Cambrian Stage 2) through the ‘middle’ Cambrian (Series 3); their apparent decline in the latest Cambrian may be partly taphonomic. The cone-in-cone construction of hallucigeniid sclerites is shared with the sclerotized cuticular structures (jaws and claws) in modern onychophorans. More generally, our results emphasize the reciprocal importance and complementary roles of Burgess Shale-type fossils and isolated microfossils in documenting early animal evolution.

A new helcionelloid mollusk from the middle Cambrian Burgess Shale, Canada

2013 ◽  
Vol 87 (6) ◽  
pp. 1067-1070 ◽  
Author(s):  
Simon Conway Morris ◽  
John S. Peel
Keyword(s):  
British Columbia ◽  
New Species ◽  
Cambrian Explosion ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Marine Life ◽  
A New Species

Burgess Shale-type faunas provide unique insights into the Cambrian “explosion”. Their degree of representativeness of Cambrian marine life in general is, however, less easy to establish. One line of evidence is to consider only the skeletal component of a Burgess Shale-type fauna and compare that with a typical Cambrian assemblage. This paper describes a new species of helcionelloid mollusk (Totoralia reticulata n. sp.) from the middle Cambrian Burgess Shale of British Columbia. Whilst much rarer than the co-occurring smooth shelled helcionelloid Scenella amii, the strongly costate morphology of Totoralia reinforces comparisons with Cambrian shelly faunas. The extension of the range of Totoralia from Argentina to Canada adds support to the proposed derivation of the Precordillera terrane of Mendoza from Laurentia.

scholarly journals Burgess Shale fossils shed light on the agnostid problem

2019 ◽  
Vol 286 (1894) ◽  
pp. 20182314 ◽  
Author(s):  
J. Moysiuk ◽  
J.-B. Caron
Keyword(s):  
British Columbia ◽  
Digestive Tract ◽  
Soft Tissues ◽  
Sister Group ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Important Group ◽  
Alternative Hypotheses ◽  
Shed Light

Agnostids (agnostinids and eodiscinids) are a widespread and biostratigraphically important group of Cambro-Ordovician euarthropods whose evolutionary affinities have been highly controversial. Their dumbbell-shaped calcified tergum was traditionally suggested to unite them with trilobites, but agnostinids have alternatively been interpreted as stem-crustaceans, based on Orsten larval material from the Cambrian of Sweden. We describe exceptionally preserved soft tissues from mature individuals of the agnostinids Peronopsis and Ptychagnostus from the middle Cambrian (Wuliuan Stage) Burgess Shale (Walcott Quarry and Marble Canyon, British Columbia, Canada), facilitating the testing of alternative hypotheses. The digestive tract includes conspicuous ramifying cephalic diverticulae. The cephalon carries one pair of elongate spinous antennules projecting to the front, two pairs of appendages with distally setose, oar-like exopods, and three pairs of presumably biramous appendages with endopods sporting club-shaped exites. The trunk bears five appendage pairs, at least the first two of which are similar to the posteriormost cephalic pairs. The combined evidence supports a nektobenthic and detritivorous lifestyle for agnostinids. A head with six appendiferous segments contrasts strikingly with the four known in trilobites and five typical of mandibulates. Agnostinids are retrieved as the sister group to polymeroid trilobites in our phylogeny, implying that crustacean-like morphologies evolved homoplastically. This result highlights the variability in segmental composition of the artiopodan head. Finally, our study emphasizes the continued role of Burgess Shale-type fossils in resolving the affinities of problematic biomineralizing taxa.

Cambrian Naraoiids (Arthropoda): Morphology, Ontogeny, Systematics, and Evolutionary Relationships

2007 ◽  
Vol 81 (S68) ◽  
pp. 1-52 ◽  
Author(s):  
X.-L. Zhang ◽  
D.-G. Shu ◽  
D. H. Erwin
Keyword(s):  
Wide Distribution ◽  
Cambrian Explosion ◽  
Valid Species ◽  
Original Material ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
Evolutionary Changes ◽  
Life Mode ◽  
Close Relatives ◽  
Chengjiang Lagerstätte

Naraoiids, defined as lightly sclerotized arthropods with a dimidiate tergum of two sclerites separated by a single transverse articulation, have been found in the Cambrian and Silurian. During the Cambrian they had a wide distribution coinciding with trilobite realms. This pattern may be related to the breakup of a Neoproterozoic supercontinent, probably Pannotia, which implies that naraoiids originated before the Cambrian “explosion.” Based on new observations on the original material from the Burgess Shale (Middle Cambrian, British Columbia),Naraoia haliais reconsidered as a valid species. The validity is further confirmed by a new record of the occurrence of this species in the Chengjiang Lagerstätte (Lower Cambrian, China). In addition, some structures ofN. compactaof the Burgess Shale have been reinterpreted. Two more naraoiid species are redescribed in detail from the Chengjiang Lagerstätte on the basis of more than 1,000 well-preserved specimens.Naraoia spinosashows dimorphism andMisszhouia longicaudataexhibits geographical variation in the overall shape of the dorsal exoskeleton. Naraoiids may have a protaspis-like larva, but the previously assigned protaspis has proven to be a separate taxon,Primicaris. In dorsal view, naraoiids resemble a giant “degree 0” meraspis (i.e., without thorax), and could have originated from different heterochronic processes, neoteny or hypermorphosis. Naraoiids are generally accepted as vagrant benthos. A predatory/scavenging life mode is supported by functional morphology and recent analogues. A healed injury inM. longicaudatasuggests that they could be the prey of larger predators, most likely anomalocaridids. We suggest that differences in exopod composition might represent evolutionary changes through the Early–Middle Cambrian. The monophyly of the Naraoiidae is not firmly established. Similarity to liwiids, supposed to be the close relatives of naraoiids, is limited to overall shape. We exclude naraoiids from the Trilobita, though there do exist a number of similarities between them.

scholarly journals New fossil assemblages from the Early Ordovician Fezouata Biota

2022 ◽  
Author(s):  
Farid Saleh ◽  
Romain Vaucher ◽  
Muriel VIDAL ◽  
Khadija EL HARIRI ◽  
Lukáš Laibl ◽  
...  
Keyword(s):  
Cambrian Explosion ◽  
Burgess Shale ◽  
Filter Feeding ◽  
Early Ordovician ◽  
Density Flow ◽  
Fossil Assemblages ◽  
Fossil Preservation

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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