Concluding remarks

1985 ◽  
Vol 311 (1148) ◽  
pp. 187-192 ◽  
Keyword(s):  
Soft Part ◽  
Burgess Shale ◽  
Exceptional Preservation ◽  
Mazon Creek ◽  
Research Programmes ◽  
Evolutionary Context ◽  
History Of ◽  
Partial Success ◽  
Solnhofen Limestone

Charles Walcott’s discovery of the Burgess Shale was by no means the first exceptional fossil locality with soft-part preservation to be unearthed, but in many ways his publications (spanning 1910-1931) provide a landmark in the history of the documentation of soft-bodied fossil biotas. Over the last 50 years the record and interpretation of exceptional preservation has grown dramatically. Milestones include the recognition of the exquisitely preserved microbiotas of the Precambrian Gunflint Chert (Barghoorn & Tyler 1965) and Bitter Springs Chert (Schopf 1968) (see also Knoll, this symposium), the superb palaeoecological and taphonomic documentation of the Carboniferous Mecca and Logan quarries (Zangerl & Richardson 1963), the continuing research programmes on deposits such as the Carboniferous Mazon Creek (Nitecki 1979; see also Baird et al. (this symposium) and Broadhurst (this symposium)), the Jurassic Solnhofen Limestone (Barthel 1978) and comparable lithographic limestones such as those of Cerin (Jurassic), Lebanon (Cretaceous) and M ontana (Carboniferous), the Jurassic Posidonia Shales (Seilacher 1982; Seilacher et al. , this symposium) and other bituminous deposits (Martill, this symposium) and the various Ediacaran sequences (Glaessner 1984; Fedonkin, this symposium). There have been impressive advances in our understanding of these and many other biotas, not least the meticulous morphological descriptions of exquisitely preserved material. The broad aim of this meeting was to try and set such exceptional deposits in a broader ecological and evolutionary context, and while we may hope to claim partial success there remain a series of interrelated points, five of which receive brief attention here.

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 A review of dinosaurian body fossils from British Columbia, Canada

2015 ◽  
Author(s):  
Iain J Reid
Keyword(s):  
United States ◽  
British Columbia ◽  
Western United States ◽  
Burgess Shale ◽  
History Of ◽  
Prairie Provinces

Since the 1900s, dinosaur fossils have been discovered from Jurassic to Cretaceous age strata, from all across the prairie provinces of Canada and the Western United States, yet little material is known from the outer provinces and territories. In British Columbia, fossils have long been uncovered from the prevalent mid-Cambrian Burgess Shale, but few deposits date from the Mesozoic, and few of these are dinosaurian. The purpose of this paper is to review the history of dinosaurian body fossils in British Columbia. The following dinosaurian groups are represented: coelurosaurians, thescelosaurids, iguanodontians, ankylosaurs and hadrosaurs.

The “evolution” of Anomalocaris and its classification in the arthropod class Dinocarida (nov.) and order Radiodonta (nov.)

1996 ◽  
Vol 70 (2) ◽  
pp. 280-293 ◽  
Author(s):  
Desmond Collins
Keyword(s):  
British Columbia ◽  
Sea Cucumber ◽  
Great Difficulty ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
The Past ◽  
History Of ◽  
The Many ◽  
Life On Earth ◽  
Mistaken Identification

The remarkable “evolution” of the reconstructions of Anomalocaris, the extraordinary predator from the 515 million year old Middle Cambrian Burgess Shale of British Columbia, reflects the dramatic changes in our interpretation of early animal life on Earth over the past 100 years. Beginning in 1892 with a claw identified as the abdomen and tail of a phyllocarid crustacean, parts of Anomalocaris have been described variously as a jellyfish, a sea-cucumber, a polychaete worm, a composite of a jellyfish and sponge, or have been attached to other arthropods as appendages. Charles D. Walcott collected complete specimens of Anomalocaris nathorsti between 1911 and 1917, and a Geological Survey of Canada party collected an almost complete specimen of Anomalocaris canadensis in 1966 or 1967, but neither species was adequately described until 1985. At that time they were interpreted by Whittington and Briggs to be representatives of “a hitherto unknown phylum.”Here, using recently collected specimens, the two species are newly reconstructed and described in the genera Anomalocaris and Laggania, and interpreted to be members of an extinct arthropod class, Dinocarida, and order Radiodonta, new to science. The long history of inaccurate reconstruction and mistaken identification of Anomalocaris and Laggania exemplifies our great difficulty in visualizing and classifying, from fossil remains, the many Cambrian animals with no apparent living descendants.

scholarly journals Waptia fieldensis Walcott, a mandibulate arthropod from the middle Cambrian Burgess Shale

2018 ◽  
Vol 5 (6) ◽  
pp. 172206 ◽  
Author(s):  
Jean Vannier ◽  
Cédric Aria ◽  
Rod S. Taylor ◽  
Jean-Bernard Caron
Keyword(s):  
Evolutionary History ◽  
The Body ◽  
Formal Description ◽  
Front Part ◽  
Burgess Shale ◽  
Middle Cambrian ◽  
History Of ◽  
Ellipsoid Bodies ◽  
Active Swimming ◽  
Prey Items

Waptia fieldensis Walcott, 1912 is one of the iconic animals from the middle Cambrian Burgess Shale biota that had lacked a formal description since its discovery at the beginning of the twentieth century. This study, based on over 1800 specimens, finds that W. fieldensis shares general characteristics with pancrustaceans, as previous authors had suggested based mostly on its overall aspect. The cephalothorax is covered by a flexible, bivalved carapace and houses a pair of long multisegmented antennules, palp-bearing mandibles, maxillules, and four pairs of appendages with five-segmented endopods—the anterior three pairs with long and robust enditic basipods, the fourth pair with proximal annulations and lamellae. The post-cephalothorax has six pairs of lamellate and fully annulated appendages which appear to be extensively modified basipods rather than exopods. The front part of the body bears a pair of stalked eyes with the first ommatidia preserved in a Burgess Shale arthropod, and a median ‘labral’ complex flanked by lobate projections with possible affinities to hemi-ellipsoid bodies. Waptia confirms the mandibulate affinity of hymenocarines, retrieved here as part of an expanded Pancrustacea, thereby providing a novel perspective on the evolutionary history of this hyperdiverse group. We construe that Waptia was an active swimming predator of soft prey items, using its anterior appendages for food capture and manipulation, and also potentially for clinging to epibenthic substrates.

Lateglacial environmental change in Scotland

2017 ◽  
Vol 110 (1-2) ◽  
pp. 173-198 ◽  
Author(s):  
Mike WALKER ◽  
John LOWE
Keyword(s):  
Environmental Change ◽  
Ice Cores ◽  
Future Research ◽  
Spatial And Temporal Patterns ◽  
Exposure Dating ◽  
Time Period ◽  
Stratigraphic Subdivision ◽  
Event Stratigraphy ◽  
Research Programmes ◽  
History Of

ABSTRACTThis paper reviews the evidence for environmental change during the Lateglacial period (c.14.7–11.7 ka), perhaps the most intensively studied episode in the Quaternary history of Scotland. It considers first the stratigraphic subdivision and nomenclature of the Lateglacial, before proceeding to a discussion of the various lines of proxy evidence that have been used to reconstruct the spatial and temporal patterns of environmental change during this time period. These include pollen and plant macrofossil data; coleopteran and chironomid records; diatom data; stable isotope and geochemical records; and evidence for human activity. The paper then considers the principal methods that have been employed to date and correlate Lateglacial events: radiocarbon dating; surface exposure dating; varve chronology; and tephrochronology. This is followed by an examination of the constraints imposed on environmental reconstructions, an account of the ways in which the evidence can be employed in the development of an event stratigraphy for the Lateglacial in Scotland, and a proposal for a provisional Lateglacial type sequence (stratotype) at Whitrig Bog in SE Scotland. Emphasis is placed throughout on the potential linkages between the Scottish records and the isotopic signal in the Greenland ice cores, which forms the stratigraphic template for the N Atlantic region. The paper concludes with a discussion of the strategies and approaches that should underpin future research programmes on Lateglacial environmental change in Scotland.

Late Proterozoic–Early Phanerozoic ‘Taphonomic Windows’: The Environmental and Temporal Distribution of Recurrent Modes of Exceptional Preservation

2014 ◽  
Vol 20 ◽  
pp. 289-313
Author(s):  
Patrick J. Orr
Keyword(s):  
Evolutionary Biology ◽  
Intermediate Phase ◽  
Temporal Distribution ◽  
Exceptional Preservation ◽  
Global Environmental ◽  
History Of ◽  
Type Preservation ◽  
Late Neoproterozoic ◽  
Diagenetic History ◽  
Organic Remains

Exceptional biotas—those in which the non-biomineralized tissues of organisms are preserved—are an important record of the evolutionary biology of the late Neoproterozoic—early Phanerozoic interval. Most of these biotas exhibit one of four modes of preservation: preservation of either 1) internal and external detail (Doushantuo-type preservation) or, 2) external cuticles (Orsten-type preservation) in calcium phosphate; 3) coating in pyrite films and infills (Beecher's Bed-type preservation); and 4) preservation of organic remains (Burgess Shale-type preservation). The global environmental and temporal distribution of each mode of preservation is reasonably well constrained, but not why these taphonomic windows existed when they did. The late Neoproterozoic – early Phanerozoic interval is characterized by complex, interlinked, physical, geochemical and biological changes to the Earth's biosphere and geosphere. The changing ecology of marine environments (from matground to mixgrounds: the ‘Agronomic Revolution’) occurred via an intermediate phase of stiffened, but not microbially bound sediments that extended the interval over which exceptional preservation occurred. Prolonged eustatic sea-level rise across flat-lying continental platforms ensured environments conducive to exceptional preservation were developed and, critically, sustained over large contiguous areas. During this, regolith on continental surfaces was recycled, providing an integral source of sediment and ions relevant to mineral authigenesis. Superimposed on these broad-scale changes are specific drivers that controlled the duration of individual taphonomic windows; elucidating these requires a better understanding of the environmental context and diagenetic history of fossiliferous successions at the intra-basinal scale.

The disparity of the Burgess Shale arthropod fauna and the limits of cladistic analysis: why we must strive to quantify morphospace

Paleobiology ◽  
1991 ◽  
Vol 17 (4) ◽  
pp. 411-423 ◽  
Author(s):  
Stephen Jay Gould
Keyword(s):  
Evolutionary Relationship ◽  
Cladistic Analysis ◽  
Difficult Problem ◽  
High Rank ◽  
Burgess Shale ◽  
Taxonomic Rank ◽  
Arthropod Fauna ◽  
Active Stabilization ◽  
History Of

Three major arguments have been raised against the crucial claim, documented by Whittington and colleagues for the Burgess Shale fauna, and so contrary to traditional views, that disparity of anatomical design reached an early maximum in the history of multicellular life: (1) the presence of many early taxa with low membership and high rank is an artifact of naming; (2) cladistic analysis of Burgess arthropods negates the claim for greater early disparity; and (3) Whittington's argument is a retrospective fallacy based on assigning high rank to differentia only by virtue of their later capacity to define major branches. I show that all these arguments are either false or illogical, and that the claim for increased early disparity is justified: (1) Taxonomic rank is an artifact, but no one has ever based a claim for greater disparity on this false criterion. (2) Cladistics can only deal with branching order, whereas disparity is a phenetic issue. These two legitimate aspects of evolutionary “relationship” are logically distinct. The rooting of a cladogram only illustrates monophyletic ancestry (which no one doubts, as we are not creationists), and cannot measure disparity. (3) The active stabilization of the differentia ofBaupläne(for genetic and developmental reasons only dimly understood) provides a powerful rationale for weighting these characters in considerations of disparity; nothing had so stabilized in the Burgess fauna. If these differentia were steadily changing contingencies, rather than actively stabilized features with “deep” architectural status, then the retrospective argument would be justified. Although the three arguments are wrong, the claim for greater early disparity cannot be confidently established until we develop quantitative techniques for the characterization of morphospace and its differential filling through time. This is a dauntingly difficult problem, much harder than cladistic ordering, but not intractable.

scholarly journals The Aquilegia genome: adaptive radiation and an extraordinarily polymorphic chromosome with a unique history

2018 ◽  
Author(s):  
Danièle Filiault ◽  
Evangeline S. Ballerini ◽  
Terezie Mandáková ◽  
Gökçe Aköz ◽  
Nathan Derieg ◽  
...  
Keyword(s):  
Adaptive Radiation ◽  
Evolutionary History ◽  
Wide Distribution ◽  
Allele Sharing ◽  
Sequencing Data ◽  
High Coverage ◽  
The World ◽  
Entire Chromosome ◽  
Evolutionary Context ◽  
History Of

AbstractThe columbine genus Aquilegia is a classic example of an adaptive radiation, involving a wide variety of pollinators and habitats. Here we present the genome assembly of A. coerulea ‘Goldsmith’, complemented by high-coverage sequencing data from 10 wild species covering the world-wide distribution. Our analyses reveal extensive allele sharing among species and demonstrate that introgression and selection played a role in the Aquilegia radiation. We also present the remarkable discovery that the evolutionary history of an entire chromosome differs from that of the rest of the genome – a phenomenon which we do not fully understand, but which highlights the need to consider chromosomes in an evolutionary context.

scholarly journals Alveolar soft part sarcoma of extremity

2020 ◽  
Vol 8 (10) ◽  
pp. 3735
Author(s):  
Shilpa Kaushal ◽  
Muninder K. Negi
Keyword(s):  
Vascular Invasion ◽  
Soft Part ◽  
External Beam Radiotherapy ◽  
Distant Metastases ◽  
Surgical Excision ◽  
Alveolar Soft Part Sarcoma ◽  
High Likelihood ◽  
Histopathological Feature ◽  
History Of ◽  
Slow Growing

Alveolar soft-part sarcoma (ASPS) is an extremely rare connective tissue tumor, predominantly seen in adolescents and young adults, with a female preponderance. Alveolar soft-part sarcoma (ASPS) is a slow growing tumor, but with high likelihood of metastasis, leading to high mortality. A classical histopathological feature of an alveolar pattern from the biopsy of the lesion favors the diagnosis. We report a case of 14 years old male patient who presented with a history of single painless swelling over thigh for which surgical excision was done. Histopathology was suggestive of Alveolar soft-part sarcoma (ASPS). There was no evidence of distant metastases. He was treated with external beam radiotherapy in view of vascular invasion.

Sign in / Sign up

Export Citation Format

Share Document