scholarly journals Arthropods from North Greenland: exceptional data in the ‘Cambrian explosion’ debate

1992 ◽  
Vol 6 ◽  
pp. 44-44
Author(s):  
Graham E. Budd
Keyword(s):  
Morphological Changes ◽  
Three Dimensional ◽  
Cambrian Explosion ◽  
Burgess Shale ◽  
Phylogenetic Methods ◽  
Fossil Material ◽  
Body Patterning ◽  
Bare Bones ◽  
Early Metazoan ◽  
North Greenland

'Sirius Passet’ fauna arthropods from the Lower Cambrian Buen Formation of North Greenland form the major component of this exceptionally preserved biota. Early mineralisation of body cavities led to internal anatomy being preserved more readily than external structures such as limbs. Musculature and gut are known in three dimensional form. Many of the taxa present are more easily compared to extant arthropods than to flattened fossil material such as from the Burgess Shale.The most common arthropod is represented by some 1600 specimens. Although widely differing in preservational style, these specimens may be reconciled to provide a coherent model of the three-dimensional anatomy of the arthropod. The affinities of this arthropod lie with the ‘Cheliceromorph’ rather than the Crustacean biramous-limbed arthropods, and may represent a fairly advanced lineage within the clade.Recent discussions of the patterns produced by the early metazoan radiations have concentrated on data available from the Burgess Shale. The continuing discovery and description of other Cambrian lagerstätten such as from North Greenland and Chengjiang has highlighted the degree to which the Burgess Shale fauna should be considered to be an aliquot taken from the foment of the ‘Cambrian Explosion’. The discovery of more taxa is tending to flesh out the bare bones of the Burgess fauna. Conclusions about phylogentic patterns drawn from the Burgess Shale alone may thus be premature.Body patterning in the arthropods, and the validity of the ‘Bauplan’ concept may be investigated by consideration of the actual mechanisms available for profound morphological change. One promising route is provided by the ‘homeotic’ and other hierarchically arranged developmental genes. When the mode of action of these genes is considered in conjunction with phylogenetic methods, it may prove possible to assess evolutionary pathways in terms of the feasibility of the morphological changes required by them rather than relying on what seems inherently reasonable or on marginal advantages in parsimony. Exceptionally preserved biotas also contain the evidence for the evolution of the developmental mechanisms themselves.

A new arthropod Pygmaclypeatus daziensis from the Early Cambrian Chengjiang Lagerstätte, South China

2000 ◽  
Vol 74 (5) ◽  
pp. 979-982 ◽  
Author(s):  
Xingliang Zhang ◽  
Jian Han ◽  
Degan Shu
Keyword(s):  
South China ◽  
Fossil Record ◽  
South Australia ◽  
Early Cambrian ◽  
Burgess Shale ◽  
Closely Related Species ◽  
Stratigraphic Position ◽  
Chengjiang Lagerstätte ◽  
Early Metazoan ◽  
North Greenland

The early Cambrian Chengjiang Lagerstatte, generally regarded as late Atdabanian (Qian and Bengtson, 1989; Bengtson et al., 1990), has become celebrated for perhaps the earliest biota of soft-bodied organisms known from the fossil record and has proven to be critical to our understanding of early metazoan evolution. The Sirius Passet fauna from Peary Land, North Greenland, another important repository of soft-bodied and poorly sclerotized fossils, was also claimed as Early Cambrian (Conway Morris et al., 1987; Budd, 1995). The exact stratigraphic position of the Sirius Passet fauna (Buen Formation) is still uncertain, although the possibility of late Atdabanian age was proposed (Vidal and Peel, 1993). Recent work dates it in the “Nevadella” Biozone (Budd and Peel, 1998). It therefore appears to be simultaneous with or perhaps slightly younger than Chengjiang Lagerstatte, Eoredlichia Biozone (Zhuravlev, 1995). The Emu Bay Shale of Kangaroo Island, South Australia, has long been famous as a source of magnificent specimens of the trilobites Redlichia takooensis and Hsunaspis bilobata. It is additionally important as the only site in Australia so far to yield a Burgess-Shale-type biota (Glaessner, 1979; Nedin, 1992). The Emu Bay Shale was considered late Early Cambrian in age (Daily, 1956; Öpik, 1975). But Zhang et al.(1980) reassessed its age based on data from the Chinese Early Cambrian. The occurrence of Redlichia takooensis and closely related species of Hsunaspis indicates an equivalence to the Tsanglangpuian in the Chinese sequence, and the contemporary South Australia fauna correlate with the Botomian of Siberia (Bengtson et al., 1990). Thus the Emu Bay Shale is younger than the upper Atdabanian Chengjiang Lagerstatte, Chiungchussuian.

scholarly journals Minerals in the gut: scoping a Cambrian digestive system

2016 ◽  
Vol 3 (11) ◽  
pp. 160420 ◽  
Author(s):  
K. M. Strang ◽  
H. A. Armstrong ◽  
D. A. T. Harper
Keyword(s):  
Calcium Phosphate ◽  
Digestive System ◽  
Three Dimensional ◽  
Elemental Mapping ◽  
Burgess Shale ◽  
High Concentration ◽  
Acidic Conditions ◽  
Electron Imaging ◽  
Crystal Seed ◽  
North Greenland

The Sirius Passet Lagerstätte of North Greenland contains the first exceptionally preserved mat-ground community of the Cambrian, dominated, in terms of abundance, by trilobites but particularly characterized by iconic arthropods and lobopods, some also occurring in the Burgess shale. High-resolution photography, scanning electron imaging and elemental mapping have been carried out on a variety of specimens of the non-mineralized arthropod Campanamuta mantonae (Budd 2011 J. Syst. Palaeontol. 9 , 217–260 ( doi:10.1080/14772019.2010.492644 )) which has three-dimensional gut and muscle preservation. Results show that the guts contain a high concentration of calcium phosphate (approximating to the mineral francolite), whereas the adjacent muscles are silicified. This indicates a unique, tissue-specific taphonomy for this Cambrian taxon. We hypothesize that the precipitation of calcium phosphate in the guts occurs rapidly after death by ‘crystal seed’ processes in suboxic, slightly acidic conditions; critically, the gut wall remained intact during precipitation. We postulate that the calcium phosphate was derived from ingested cellular material. Silicification of the muscles followed as the localized water chemistry became saturated in silica, high in Fe 2+ , and low in oxygen and sulfate. We document here the unique occurrence of two distinct but mechanistically similar taphonomic pathways within a diverse suite of possibilities in an Early Cambrian Lagerstätte.

scholarly journals A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources

2019 ◽  
Vol 286 (1908) ◽  
pp. 20191079 ◽  
Author(s):  
J. Moysiuk ◽  
J.-B. Caron
Keyword(s):  
British Columbia ◽  
Feeding Ecology ◽  
Food Sources ◽  
Cambrian Explosion ◽  
Feeding Apparatus ◽  
Burgess Shale ◽  
Apex Predators ◽  
Oral Cone ◽  
Fossil Material ◽  
Spinous Processes

Radiodonts, a clade of Cambro-Devonian stem group euarthropods, have classically been regarded as nektonic apex predators. However, many aspects of radiodont morphology and ecology have remained unclear because of the typically fragmentary nature of fossil material. Here, we describe a new hurdiid radiodont based on abundant and exceptionally well-preserved fossils from the Burgess Shale (Marble Canyon area, British Columbia, Canada). Cambroraster falcatus gen. et sp. nov . is characterized by an extra-large horseshoe-shaped head carapace, bearing conspicuous posterolateral spinous processes, and partially covering a short trunk with eight pairs of lateral flaps. Each of the pair of frontal appendages possess five mesially curving rake-like endites equipped with a series of anteriorly directed hooked spines, altogether surrounding the oral cone. This feeding apparatus suggests a micro to macrophagous sediment-sifting feeding ecology. Cambroraster illuminates the evolution of Hurdiidae and evinces the exploitation of the diversifying infauna by these large and specialized nektobenthic carnivores in the aftermath of the Cambrian explosion.

Thermal characterization of ABS-Graphene blended three dimensional printed functional prototypes for electro chemical energy storage

2018 ◽  
Vol 1 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Kamaljit Singh Boparai ◽  
Rupinder Singh
Keyword(s):  
Energy Storage ◽  
Structural Changes ◽  
Fused Deposition Modeling ◽  
Morphological Changes ◽  
Three Dimensional ◽  
Thermal Characterization ◽  
Chemical Energy ◽  
Flow Index ◽  
Fused Deposition

This study highlights the thermal characterization of ABS-Graphene blended three dimensional (3D) printed functional prototypes by fused deposition modeling (FDM) process. These functional prototypes have some applications as electro-chemical energy storage devices (EESD). Initially, the suitability of ABS-Graphene composite material for FDM applications has been examined by melt flow index (MFI) test. After establishing MFI, the feedstock filament for FDM has been prepared by an extrusion process. The fabricated filament has been used for printing 3D functional prototypes for printing of in-house EESD. The differential scanning calorimeter (DSC) analysis was conducted to understand the effect on glass transition temperature with the inclusion of Graphene (Gr) particles. It has been observed that the reinforced Gr particles act as a thermal reservoir (sink) and enhances its thermal/electrical conductivity. Also, FT-IR spectra realized the structural changes with the inclusion of Gr in ABS matrix. The results are supported by scanning electron microscopy (SEM) based micrographs for understanding the morphological changes.

Articulated halkieriids from the Lower Cambrian of North Greenland and their role in early protostome evolution

1995 ◽  
Vol 347 (1321) ◽  
pp. 305-358 ◽  
Keyword(s):  
Body Size ◽  
Molecular Biology ◽  
Lower Cambrian ◽  
Burgess Shale ◽  
Internal Anatomy ◽  
Middle Cambrian ◽  
Functional Consequence ◽  
Primitive State ◽  
North Greenland

Articulated halkieriids of Halkieria evangelista sp. nov. are described from the Sirius Passet fauna in the Lower Cambrian Buen Formation of Peary Land, North Greenland. Three zones of sclerites are recognizable: obliquely inclined rows of dorsal palmates, quincuncially inserted lateral cultrates and imbricated bundles of ventro-lateral siculates. In addition there is a prominent shell at both ends, each with radial ornamentation. Both sclerites and shells were probably calcareous, but increase in body size led to insertion of additional sclerites but marginal accretion of the shells. The ventral sole was soft and, in life, presumably muscular. Recognizable features of internal anatomy include a gut trace and possible musculature, inferred from imprints on the interior of the anterior shell. Halkieriids are closely related to the Middle Cambrian Wixaxia , best known from the Burgess Shale: this clade appears to have played an important role in early protostome evolution. From an animal fairly closely related to Wixaxia arose the polychaete annelids; the bundles of siculate sclerites prefigure the neurochaetae whereas the dorsal notochaetae derive from the palmates. Wixaxia appears to have a relic shell and a similar structure in the sternaspid polychaetes may be an evolutionary remnant. The primitive state in extant polychaetes is best expressed in groups such as chrysopetalids, aphroditaceans and amphinomids. The homology between polychaete chaetae and the mantle setae of brachiopods is one line of evidence to suggest that the latter phylum arose from a juvenile halkieriid in which the posterior shell was first in juxtaposition to the anterior and rotated beneath it to provide the bivalved condition of an ancestral brachiopod. H. evangelista sp. nov. has shells which resemble those of a brachiopod; in particular the posterior one. From predecessors of the halkieriids known as siphogonuchitids it is possible that both chitons (polyplacophorans) and conchiferan molluscs arose. The hypothesis of halkieriids and their relatives having a key role in annelid—brachiopod—mollusc evolution is in accord with some earlier proposals and recent evidence from molecular biology. It casts doubt, however, on a number of favoured concepts including the primitive annelid being oligochaetoid and a burrower, the brachiopods being deuterostomes and the coelom being an archaic feature of metazoans. Rather, the annelid coelom arose as a functional consequence of the transition from a creeping halkieriid to a polychaete with stepping parapodial locomotion.

scholarly journals Right Ventricular Global and Regional Remodeling in American-Style Football Athletes: A Longitudinal 3D Echocardiographic Study

2021 ◽  
Vol 11 (8) ◽  
pp. 3357
Author(s):  
Amir Hodzic ◽  
Gabriel Bernardino ◽  
Damien Legallois ◽  
Patrick Gendron ◽  
Hélène Langet ◽  
...  
Keyword(s):  
Right Ventricular ◽  
Morphological Changes ◽  
Three Dimensional ◽  
Computational Method ◽  
Physiological Adaptation ◽  
Volumetric Assessment ◽  
American Style ◽  
Few Data ◽  
The Right ◽  
Field Position

Few data exist concerning the right ventricular (RV) physiological adaptation in American-style football (ASF) athletes. We aimed to analyze the RV global and regional responses among ASF-trained athletes. Fifty-nine (20 linemen and 39 non-linemen) ASF athletes were studied before and after inter-seasonal training. During this period, which lasted 7 months, all athletes were exposed to combined dynamic and static exercises. Cardiac longitudinal changes were examined using three-dimensional transthoracic echocardiography. A computational method based on geodesic distances was applied to volumetrically parcellate the RV into apical, outlet, and inlet regions. RV global and regional end-diastolic volumes increased significantly and similarly in linemen and non-linemen after training, with predominant changes in the apex and outlet regions. RV global and regional ejection fractions were preserved. Morphological changes were uniformly distributed among the four cardiac chambers, and it was independent of the field position. Assessment of RV end-diastolic global, inlet and apical volumes showed low intra-observer (3.3%, 4.1%, and 5.3%, respectively) and inter-observer (7%, 12.2%, and 9%, respectively) variability, whereas the outlet regional volumetric assessment was less reproducible. To conclude, ASF inter-seasonal training was associated with a proportionate biventricular enlargement, regardless of the field position. Regional RV analysis allowed us to quantify the amount of exercise-induced remodeling that was larger in the apical and outlet regions.

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.

scholarly journals Chance, Evolution, and the Metaphysical Implications of Paleontological Practice

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.

scholarly journals Early fossil record of Euarthropoda and the Cambrian Explosion

2018 ◽  
Vol 115 (21) ◽  
pp. 5323-5331 ◽  
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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